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- Herausgeber: John Wiley & Sons
- Kategorie: Fachliteratur
- Sprache: Englisch
Comprehensive reference describing in-depth physical anatomy and histology of domestic avian species chicken, depicted through high quality macro- and micro-photographs Atlas of Anatomy and Histology of the Domestic Chicken is a state-of-the-art atlas of avian anatomy that provides a complete collection of both original gross anatomy and histology photographs and texts of all body systems of the birds based on the domestic chicken to depict anatomic features. Using cutting-edge technology to create visualizations of anatomic structure, this specialist reference includes both gross anatomical structures/organs and their histological details next to each other. This approach enables readers to understand the macro- and micro-pictures of each organ/structure under study. The text includes a total of more than 200 high-resolution, high quality color images and diagrams. Written by two highly qualified professors with significant experience in the field, Anatomy and Histology of the Domestic Chicken includes information on: * External features of the body, including regions, features, ornaments, shape, feathers, skin, and the uropygial gland * Musculoskeletal characteristic including cartilage and bone formation and classification, flight and ambulatory muscles * Digestive system, including the beak, esophagus, crop, proventriculus, ventriculus, intestines, and accessory glands * Respiratory system, including external nares, the nasal cavity, trachea, upper larynx, syrinx, lungs, and air sacs * Urinary system, including kidneys and the ureter, cloaca-urodeum, and genital system, covering differences between males and females * Endocrine system, including pituitary, pineal, adrenal, pancreas, thyroid, and parathyroid glands * Nervous system with central and peripheral divisions and sense organs including eye and ear * Lymphatic system, with descriptions of the primary and secondary lymphatic organs * Egg anatomy and development of the chick embryo * Applied anatomical concepts important for clinical maneuvers and necropsy With comprehensive coverage of the subject and highly detailed photographs included throughout the text, Anatomy and Histology of the Domestic Chicken is an indispensable resource for breeders, veterinarians, researchers, avian biologists, pathologists, and students in animal sciences and veterinary fields.
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Table of Contents
Cover
Table of Contents
Title Page
Copyright Page
Dedication
List of Contributors
Foreword
Preface
Acknowledgments
Lists of Abbreviations
1 External Features of Chicken
1.1 Skin
1.2 Structures Associated with the Skin
1.3 Feathers
1.4 Lamellar Corpuscles
1.5 Molting
1.6 Debeaking
1.7 Eyelids Including Third Eyelid
1.8 Vent
1.9 Uropygial Gland
1.10 Brood Pad
1.11 Bursa Sterni
1.12 Legs
1.13 Thermoregulation
References
2 Skeletal System
2.1 Introduction
2.2 Cartilage and Bone Embryonic Origin
2.3 Cartilage Cell Types
2.4 Type of Cartilages
2.5 Cartilage Development
2.6 Calcium Homeostasis
2.7 Bone Cell Types
2.8 Ossification
2.9 Axial Skeleton
2.10 Sesamoid Bones
2.11 Pneumatic Bones
2.12 Pectoral Girdle
2.13 Pectoral Limb (Wing)
2.14 Pelvic Girdle
2.15 Pelvic Limb
2.16 Arthrosis (Joints)
References
3 Muscular System
3.1 Introduction
3.2 Muscle Histology
3.3 Muscle Nomenclature
3.4 Types of Skeletal Muscle Fibers
3.5 Muscle Cells
3.6 Skeletal Muscle Blood Supply
3.7 Skeletal Muscle Innervation
3.8 Muscle Spindle
3.9 Tendon
3.10 General Description of Skeletal Muscle
3.11 Cutaneous Muscles
3.12 Flight Muscles
3.13 Muscles of the Pelvic Region
3.14 Abdominal Muscles
References
4 Digestive System
4.1 Introduction
4.2 Oral Cavity and Pharynx
4.3 Hyoid Apparatus (Hyoglossal, Hyolingual, or Hyobranchial)
4.4 Esophagus (Pars cervicalis, Crop, and Pars thoracica)
4.5 Stomach (Proventriculus and Ventriculus)
4.6 Small Intestine
4.7 Large Intestine
4.8 Cloaca
4.9 Vent
4.10 Liver (Hepar, Jecur)
4.11 Pancreas
References
5 Respiratory System
5.1 Introduction
5.2 Nostrils and Nasal Cavity
5.3 Larynx (Larynx Cranialis), Upper Larynx
5.4 Trachea
5.5 Syrinx (Larynx Caudalis), Lower Larynx
5.6 Lungs
5.7 Direction of Airflow
5.8 Blood‐Gas Barrier
5.9 Air Sacs
References
6 Urinary System
6.1 Introduction
6.2 Kidney
6.3 Ureter
6.4 Urodeum
6.5 Blood Supply
6.6 Innervation
6.7 Urine
References
7 Reproductive System
7.1 Male Reproductive System
7.2 Female Reproductive System
References
8 Endocrine System
8.1 Introduction
8.2 Physiological Balance
8.3 Major Endocrine Glands
References
9 Sense Organs
9.1 The Eye
9.2 The Ear
References
10 The Cardiovascular System
10.1 Introduction
10.2 Heart
10.3 General Arterial System
10.4 Venous System
10.5 Sites for Blood Collection
10.6 Hepatic Portal System
10.7 Renal Portal System
10.8 Carotid Body/Carotid Sinus
References
11 The Lymphatic System
11.1 Introduction
11.2 Cells of the Lymphatic System
11.3 Common Terms Used with the Lymphatic System
11.4 Primary Lymphatic Organs
11.5 Secondary Lymphatic Organs
11.6 Maternal Transfer of Immunity
11.7 Lymphatic Vessels
References
12 Nervous System
12.1 Introduction
12.2 Neuron
12.3 Ganglion
12.4 Glial Cells (Neuroglia)
12.5 Peripheral Nervous System Cells
12.6 Meninges
12.7 Brain Ventricles
12.8 Cerebrospinal Fluid (CSF)
12.9 Blood Brain Barrier
12.10 Cerebrum
12.10.4 Metencephalon (Cerebellum)
12.10.5 Myelencephalon (Medulla Oblongata)
12.11 Reticular Formation
12.12 Spinal Cord
12.13 Glycogen Bodies
12.14 Autonomic Nervous System
References
13 Applied Chicken Anatomy
13.1 Examining from a Distance
13.2 Physical Examination
13.3 Specialized Clinical Procedures
References
14 Chicken Necropsy
14.1 Introduction
14.2 Euthanasia and Carcass Disposal
14.3 Chicken Disposal
14.4 Facilities and Materials Needed
14.5 Whole Carcass Conservation
14.6 Necropsy Protocol
Further Reading
15 The Egg Anatomy
15.1 Introduction
15.2 The Germinal Disc
15.3 The Yolk
15.4 The Albumen
15.5 The Eggshell
15.5.3 Cuticle
References
16 Fertilization and Chick Embryo Development
16.1 Introduction
16.2 Avian Fertilization
16.3 Chick Embryo Development
References
Index
End User License Agreement
List of Tables
Chapter 7
Table 7.1 Functions of different segments of the hen’s oviduct with respect...
Chapter 16
Table 16.1 Simplified table describing the developmental stage of chick emb...
List of Illustrations
Chapter 1
Figure 1.1 (A and B) Histology sections of abdominal chicken skin. This extr...
Figure 1.2 Female (A) and male (B) head external features. (a) Single comb, ...
Figure 1.3 Comb of young (A) and adult rooster (B) showing keratinized strat...
Figure 1.4 Wattle of a rooster showing thin keratinized stratified squamous ...
Figure 1.5 (A) Ventral view of a plucked adult rooster. (a) Lateral cervical...
Figure 1.6 Rooster alular feathers (short flight feathers, usually three) no...
Figure 1.7 Adult feather from the tail. (a) Inferior umbilicus, (b) calamus ...
Figure 1.8 Wing feathers of a chicken. (a) Alulae, (b) primary feathers, (c)...
Figure 1.9 Relative size of feathers. (A) Primary feather covert from dorsal...
Figure 1.10 Relative size of contour feathers with after feathers (arrows) f...
Figure 1.11 (A and B) Adult rooster vent showing the transition of the epith...
Figure 1.12 Vent of a hen. (a) Dorsal lip, (b) ventral lip, (c) commissure, ...
Figure 1.13 Histology photos of the uropygial gland of a chicken showing the...
Figure 1.14 Dorsal view of a right metatarsal and digits of adult male chick...
Figure 1.15 (A and B) Digital pad of an adult hen showing a highly keratiniz...
Chapter 2
Figure 2.1 Hindlimbs radiograph of a chicken showing the (a) radiopaque oute...
Figure 2.2 Chicken skeleton showing the directional terms.
Figure 2.3 Different anatomical regions of a long bone (example used is tibi...
Figure 2.4 Chicken skull lateral view (a) premaxilla, (b) maxilla, (c) openi...
Figure 2.5 Shoulder girdle and the sternum articulating with the synsacrum a...
Figure 2.6 Thoracic vertebra with a pair of ribs attached to it showing (a) ...
Figure 2.7 Chicken sternum showing (a) manubrial spine (sternum rostrum), (b...
Figure 2.8 Left chicken humerus, (a) caput (head) of the humerus with (b) pn...
Figure 2.9 Pectoral (shoulder) girdle showing the scapula and the coracoid b...
Figure 2.10 The chicken furcula shows (a) ramus and (b) hypocledium.
Figure 2.11 (A and B). Left medial and lateral chicken humerus, (A) medial v...
Figure 2.12 Right chicken wing without the humerus, (A) medial view and (B) ...
Figure 2.13 A chicken radiograph showing the (a) scapula, (b) coracoid, (c) ...
Figure 2.14 Left femur of chicken (A) caudomedial view and (B) caudolateral ...
Figure 2.15 Chicken right tibiotarsus and fibula (A) cranial view, (a) patel...
Chapter 3
Figure 3.1 The inner cloacal surface of a chicken shows (a) smooth muscles w...
Figure 3.2 A section in the wall of the chicken intestine shows the three la...
Figure 3.3 The longitudinal section of chicken cardiac muscle shows striatio...
Figure 3.4 A section in the outer region of the cloacal opening shows (a) no...
Figure 3.5 A cross section of the thigh red muscle of adult chicken. Notice ...
Figure 3.7 Dissected dorsal view of the muscles of the back of the chicken. ...
Figure 3.8 Dissected chicken, ventral view. (a) Trachea, (b) esophagus, (c) ...
Figure 3.9 Dissected chicken left lateral view. (a) Trachea, (b) esophagus, ...
Figure 3.10 (A) Ventral aspect of the wing of adult rooster, feathers plugge...
Figure 3.11 Dissected chicken, dorsal view. (a) and (b) latissimus dorsi m.,...
Figure 3.12 Lateral aspect of the left musculature of the adult rooster. (a)...
Figure 3.13 Medial aspect of the thigh of adult male chicken. (a) Cranial il...
Figure 3.14 Medial aspect of the thigh of embalmed adult male chicken. (a) I...
Chapter 4
Figure 4.1 Dissected chicken digestive tract. Tongue (a), larynx (b), cervic...
Figure 4.2 Open mouth of a male chicken (left), floor (middle), and roof (ri...
Figure 4.3 Palatine mucosa histological section. H&E stain. Palatine papilla...
Figure 4.4 Left side view of the head of a female chicken. The beak is point...
Figure 4.5 Histological transverse section of the tongue. Trichrome stain. T...
Figure 4.6 Floor (left) and roof (right) of the oropharyngeal cavity. In the...
Figure 4.7 Dorsal view of the hyoid bone (left drawing based on McLelland 19...
Figure 4.8 Right lateral view of the cervical and thoracic regions. (a) Phar...
Figure 4.9 Section of the cervical portion of the esophagus. Trichrome. The ...
Figure 4.10 Chicken stomach seen from the left side. (A) External and (B and...
Figure 4.11 (A) Histological section of the proventriculus of the chicken st...
Figure 4.12 Histological section of the intermediate zone (isthmus) of the c...
Figure 4.13 Gizzard (ventriculus). H&E stain A, B, and C. Koilin (a), surfac...
Figure 4.14 Abdominal organs of a male adult chicken (liver and spleen are r...
Figure 4.15 Histological section of the chicken duodenum. H&E stain. Villi (...
Figure 4.16 Histological section of the jejunum. Trichrome stain. Villi (a),...
Figure 4.17 Histological section of the ileum. Trichrome stain. Villi (a), s...
Figure 4.18 Histological section of the rectum (colorectum). H&E stain. The ...
Figure 4.19 (A) Histological section of the ileum (a) and ceca (b) H&E stain...
Figure 4.20 Ventral view of the chicken final portion of the digestive tract...
Figure 4.21 Histological sections of the female cloaca. Trichrome stain (A)....
Figure 4.22 Vent of a female chicken images, (A) macroscopic and (B) histolo...
Figure 4.23 Parietal (A) and visceral (B) views of a chicken liver. (A) Righ...
Figure 4.24 Histology of the chicken liver (A, B, and C). H&E stain. Central...
Figure 4.25 Histology of the chicken pancreas. (A) H&E (B) Trichrome stains....
Chapter 5
Figure 5.1 A sagittal section of a chicken head showing the nasal cavity. (a...
Figure 5.3 (A and B) Histological section of the middle nasal concha. H&E (a...
Figure 5.4 (A and B) Histological section of the rostral part of upper laryn...
Figure 5.5 Histological section of the caudal part of the upper larynx of th...
Figure 5.6 Histological section of the upper larynx. Trichrome (a) Laryngeal...
Figure 5.7 (A and B) Histological section of the trachea of a chicken. Trich...
Figure 5.8 Syrinx and surrounding structures of a chicken. (a) Trachea, (b) ...
Figure 5.9 Chicken lungs, dorsal view. (a) Trachea, (b) heart, and (c) right...
Figure 5.10 A diagrammatic representation of the trachea and air sacs of a c...
Figure 5.13 (A and B) Histological section (H&E stain) of the lung histology...
Figure 5.14 Histological section of the lung parenchyma, parabronchus. P.A.S...
Figure 5.15 (A) Histological section of the lung parenchyma and parabronchus...
Figure 5.16 Diagrams of the trachea, air sacs, and the direction of airflow ...
Chapter 6
Figure 6.1 Ventro‐dorsal view of the celomic cavity/abdominal to pelvic regi...
Figure 6.2 A cross section of several lobules within the chicken kidney, (a)...
Figure 6.3 A section in one lobule with its (a) blood vessel, (b) within the...
Figure 6.4 Half a lobule of a chicken kidney showing (a) thin connective tis...
Figure 6.6 A cross section of one renal lobule of the chicken showing the (a...
Figure 6.7 Mammalian (outer cortical) type nephron showing juxtaglomerular a...
Figure 6.8 Kidney section passing through both the cortex and part of the me...
Figure 6.9 Mammalian (cortical) type nephron in the chicken kidney showing t...
Figure 6.10 Medulla of the chicken kidney showing the mammalian type nephron...
Figure 6.11 (A) Chicken ureter cross section with (a) star‐shaped lumen, (b)...
Chapter 7
Figure 7.1 Images of the location of the testes inside the abdominal cavity ...
Figure 7.2 Histological sections of mature (A, B, C) and immature (D) chicke...
Figure 7.3 Diagrammatic representation of the extratesticular genital duct s...
Figure 7.4 Histological sections of epididymis (A and B). H&E stain. (a) Epi...
Figure 7.5 Location of the epididymis and deferent duct inside the celomic c...
Figure 7.6 Histological sections of deferent duct close to its termination t...
Figure 7.7 Diagram redrawn and based on King (1975) and (1993) of the ventra...
Figure 7.8 Higher magnification of seminiferous tubules inside the testis. H...
Figure 7.9 Diagram of a rooster sperm morphological features. (A) Entire spe...
Figure 7.10 Female reproductive tract of a mature hen (in situ). (a) Mature ...
Figure 7.11 Ovaries of a hen. (A) Mature and active ovary with follicles at ...
Figure 7.12 Histological section of a hen’s ovary (A and B). H&E stain. (a) ...
Figure 7.13 Mature follicles (yolk) of different size or developmental stage...
Figure 7.14 Excised hen’s oviduct. (a) Entrance of the infundibulum, white w...
Figure 7.15 Histological section of a hen’s infundibulum (A and B). H&E stai...
Figure 7.16 Histological section of a hen’s magnum wall (A and B). H&E stain...
Figure 7.17 Histological cross section of a hen’s uterus (shell gland). H&E ...
Figure 7.18 Histological cross section of a hen’s vagina (A and B). Trichrom...
Chapter 8
Figure 8.1 (A, B) Histological section of the chicken adenohypophysis showin...
Figure 8.2 (A, B) Histological section of chicken adrenal cortical and medul...
Figure 8.3 Histological section of the thyroid gland (A) and inset (B). (a) ...
Figure 8.4 Histological section of the thyroid gland of a chicken with part ...
Figure 8.5 (A, B) Chicken ultimobranchial body close to the bifurcation of t...
Figure 8.6 Carotid body of chicken. (a) Aggregates of carotid body (chemosen...
Figure 8.7 (A, B) Chicken pancreas showing (a) thin connective tissue capsul...
Figure 8.8 Histological section of a chicken ovary showing: (a) developing f...
Chapter 9
Figure 9.1 Chicken skull showing bones including scleral ossicle and structu...
Figure 9.2 Histological section of the chicken cornea showing (a) anterior n...
Figure 9.3 Corneal conjunctival junction, (a) cornea with non‐keratinized st...
Figure 9.4 A section through the eyeball showing the (a) cornea, (b) lens, (...
Figure 9.5 Ciliary processes arise from the (a) pars plicata (connective tis...
Figure 9.6 Histological section of the chicken lens showing (a) lens capsule...
Figure 9.7 Female chicken head showing (a) upper eyelid, (b) iris, (c) lower...
Figure 9.8 Upper eyelid of the chicken showing: (a) relatively thin stratifi...
Figure 9.9 The third eyelid of the chicken (a) attached and (b) free ends. T...
Figure 9.10 Harderian gland of the chicken (lacrimal gland of the third eyel...
Figure 9.11 Lateral view of the head of a chicken showing the external ear o...
Figure 9.12 Diagram of the chicken ear. (a) External ear, (b) middle ear, ty...
Chapter 10
Figure 10.1 Chicken heart, ventral view, (a) trachea, (b) syrinx, (c) heart ...
Figure 10.2 Chicken heart left lateral view, (a) aorta, (b) right brachiocep...
Figure 10.3 The left auricle wall sectioned at the pectinate muscle showing ...
Figure 10.4 A cross section in the wall of the chicken heart at the left ven...
Figure 10.5 A section passing through the myocardium of the chicken shows (a...
Figure 10.6 A cross section of the ascending aorta of chicken (two magnifica...
Figure 10.7 Large muscular artery with (a) thick tunica media as well as (b)...
Figure 10.8 Common carotid artery of the chicken with (a) tunica intima, (b)...
Figure 10.10 A small‐size muscular artery (a) and a vein with red blood cell...
Figure 10.11 Terminal blood vessels showing (a) arteriole, (b) venule, withi...
Figure 10.12 The ventral aspect of the chicken wing shows the course of the ...
Figure 10.13 Branches of cranial mesenteric artery in chicken. (a) Cranial m...
Figure 10.14 Chicken hindlimb showing the metatarsal blood vessel which is u...
Figure 10.15 Cervical region of the chicken showing the left external jugula...
Figure 10.16 Ventral view of the abdominal coelomic cavity showing the blood...
Figure 10.17 The illustration portrays the blood flow within the chicken's r...
Chapter 11
Figure 11.1 Chicken blood smear (stain) showing RBCs (a), monocytes (b), lym...
Figure 11.2 Chicken blood smear (stain) showing RBCs (a), heterophils (b), p...
Figure 11.3 Bursa of Fabricius (b) of a young chicken (17 weeks) inside the ...
Figure 11.4 Bursa of Fabricius, H&E stain. Follicle filled with lymphocytes ...
Figure 11.5 Chicken thymus. Right lateral (superior) and left lateral (infer...
Figure 11.6 Adult chicken thymus. (A) H&E stain showing cortex (a) and medul...
Figure 11.7 Chicken spleen. Left liver lobe (a), spleen (b), gallbladder (c)...
Figure 11.8 Chicken spleen, H&E stain. Capsule (a), red pulp (b), white pulp...
Figure 11.9 Celomic cavity with digestive organs. Cloaca (a), colorectum (b)...
Figure 11.10 Cecal tonsil of adult chicken, H&E stain. Notice the lymphatic ...
Figure 11.11 Description of the lymphatic system reaction toward pathogens a...
Figure 11.12 Harder gland section. H&E stain sections. Notice the secretory ...
Chapter 12
Figure 12.1 Histological section of a dorsal root ganglion. (a) Neuronal cel...
Figure 12.2 Autonomic ganglion of a chicken showing (a) neuronal cell bodies...
Figure 12.4 Submucosal ganglion within the wall of the upper digestive syste...
Figure 12.5 Longitudinal section of the ischiatic nerve of a chicken showing...
Figure 12.6 Chick embryo with the neural tube development and the body segme...
Figure 12.7 Dorsal view of the brain after removal of the calvarium and meni...
Figure 12.8 Sagittal section of adult chicken head. (a) Olfactory bulb, (b) ...
Figure 12.9 Section of the chicken cerebellum, (a) white matter, (b) molecul...
Figure 12.10 Sagittal section of a chicken head and neck (formalin fixed) sh...
Chapter 13
Figure 13.1 (A) The normal chicken has its thorax orientation on a horizonta...
Figure 13.2 A chicken with Marek’s disease which has the classical sign of o...
Figure 13.3 This is the Turken breed of chicken. The Turken is also known as...
Figures 13.4 (A, B) These photos are examples of feather lice (insects). (A)...
Figure 13.5 (A, B) These photos are examples of the most common feather mite...
Figure 13.6 (A, B) The cloaca should be clean and free of any fecal material...
Figure 13.7 (A) Showing a clinically healthy chicken (rooster) leg. Note the...
Figure 13.8 This photo depicts the signs of bumblefoot (pododermatitis) in w...
Figure 13.9 (A) Depicting an open mouth of the chicken which has a prominent...
Figure 13.10 (A) Depicting blood collection from the brachial (wing) vein. (...
Chapter 14
Figure 14.1 Collection of samples for microbiology, either for culture or mo...
Figure 14.2 External examination of the head. (A) Secretion associated with ...
Figure 14.3 (A) Subcutaneous observation of structures and lesions. (a) Trac...
Figure 14.4 Demonstration on how to access the celomic cavity. (A) A small i...
Figure 14.5 (A) The heart is identified inside the pericardial sac (a), in c...
Figure 14.6 (A) The liver is evaluated for position (caudal to the heart (a)...
Figure 14.7 Once the liver and heart are removed, the proventriculus (a), gi...
Figure 14.8 (A) Once the lung is dissected from the thoracic cavity, several...
Figure 14.9 Gastrointestinal tract
in situ
(A) and
ex situ
(B). (a) Esophagu...
Figure 14.10 Body of a young hen once the digestive system has been removed....
Figure 14.11 Bones and bone marrow (arrows) can be examined once other organ...
Chapter 15
Figure 15.1 Regular brown chicken egg. The pole that is more pointed is the
Figure 15.2 The two major compartments of a cracked fresh egg: the albumen (...
Figure 15.3 A diagram of a hen’s egg in a longitudinal section.
Figure 15.4 A schematic diagram section through the eggshell parts (testa an...
Chapter 16
Figure 16.1 Diagram to show the steps for sperm binding to and penetration o...
Figure 16.2 Day 2 chicken embryo. (a) Blastoderm as a clear color disc on th...
Figure 16.3 Day 3 chicken embryo. Development of extraembryonic circulation ...
Figure 16.4 Dorsal view of whole mount embryos (18 hours of development). (a...
Figure 16.5 Light micrographs of transverse sections from embryos at differe...
Figure 16.6 Diagram of a chick embryo in a longitudinal section showing the ...
Guide
Cover Page
Table of Contents
Title Page
Copyright Page
Dedication
List of Contributors
Foreword
Preface
Acknowledgments
Lists of Abbreviations
Begin Reading
Index
WILEY END USER LICENSE AGREEMENT
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Anatomy and Histology of the Domestic Chicken
Edited by
Wael Khamas
College of Veterinary MedicineWestern University of Health SciencesPomona, USA
Josep Rutllant
College of Veterinary MedicineWestern University of Health SciencesPomona, USA
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Library of Congress Cataloging‐in‐Publication Data
Names: Khamas, Wael, editor. | Rutllant, Josep, editor.Title: Anatomy and histology of the domestic chicken / edited by Wael Khamas, Josep Rutllant.Description: Hoboken, New Jersey : Wiley‐Blackwell, [2024] | Includes bibliographical references and index.Identifiers: LCCN 2024003433 (print) | LCCN 2024003434 (ebook) | ISBN 9781119841722 (cloth) | ISBN 9781119841753 (adobe pdf) | ISBN 9781119841746 (epub) | ISBN 9781119841739 (oBook)Subjects: MESH: Chickens–anatomy & histologyClassification: LCC SF767.P6 (print) | LCC SF767.P6 (ebook) | NLM SF 767.P6 | DDC 636.50891–dc23/eng/20240229LC record available at https://lccn.loc.gov/2024003433LC ebook record available at https://lccn.loc.gov/2024003434
Cover Design: WileyCover Images: © Wael Khamas and Josep Rutllant
Dedication
To My beloved family. I dedicate this book to you with profound gratitude and a heart full of love. Your support, patience, and endless encouragement have been the guide on this journey. May this book be a token of my appreciation and a reminder of the unbreakable bonds we share.
Wael Khamas
This book is dedicated to my parents, who have consistently instilled in me the treasured values of learning, diligent work, integrity, civility, and the significance of friendship. “Mai us podré tornar tot el que heu fet per mi” – I can never fully repay you for all that you've done for me. To Helena and Laura, for the boundless love and unwavering support you have graciously bestowed upon me. Lastly, to Joaquín Camón, a cherished mentor who introduced me to the world of anatomy and firmly believed in my potential. You are all notes of my music.
Josep Rutllant
List of Contributors
Wael KhamasCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Manel Lopez‐BejarCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
and
College of Veterinary SciencesUniversitat Autónoma de BarcelonaBellaterra, Spain
Thomas MarinoCollege of Veterinary MedicineWestern University of Health SciencesPomona CAUSA
Teresa Y. MorishitaCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Ken NoriegaCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Robert E. Porter JrCollege of Veterinary MedicineUniversity of MinnesotaMinneapolis, MNUSA
Josep RutllantCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Miguel D. SaggeseCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Hrvoje SmodlakaCollege of Veterinary MedicineWestern University of Health SciencesPomona, CAUSA
Foreword
The chicken…one of the most unassuming animals in the world yet its importance in agricultural food production cannot be underestimated. As a food source, chicken is the leading protein source for most of the global population. Chickens have been recommended for farming in developing countries to supply both meat and eggs. In addition, the chicken has been increasing in popularity among individual families to have them roaming in backyards for insect control, nostalgia, and food sustainability. This was most evident during the global COVID‐19 pandemic where families sought to have their own egg source for their families. In addition, the chicken has become more of a family pet so ensuring their health and welfare is also important from a veterinary medical standpoint. Unfortunately, there is a scarcity of literary resources that one can consult when working with the chicken.
Having spent my entire career working in poultry and avian medicine, I know that there is a lack of resources that are readily available. It is with great anticipation that I await the Anatomy and Histology of the Domestic Chicken. Drs. Wael Khamas and Josep Rutllant‐Labeaga have assembled a team of anatomists and veterinarians to create a most comprehensive 16‐chapter reference of the chicken anatomy and histology. The authors document all areas of the chicken starting from the external anatomy and going through each organ system, including the special senses. In addition, the authors cover a much‐needed area, which is the avian egg along with fertilization and chicken development. Never before has there been one comprehensive source on the chicken. Moreover, in addition to covering all major body parts of the chicken, the authors were very insightful to also include related clinical anatomy of the chicken, including the necropsy of the chicken which would be very useful for diagnostics and clinical poultry medicine. Moreover, the book is composed of many visually stunning photographs, including the internal anatomy of the cloaca. Many references in the past used schematic diagrams, but this is a masterpiece for readers.
This book will serve as a resource for so many individuals, from researchers to educators. At the undergraduate and graduate level, I envision this book serving as a resource for students learning zoology and biology in comparative anatomy courses; and for animal science courses, where students can learn about the chicken, a major species in agricultural production. This book will also be of interest to evolutionary biologists and paleontologists since the chicken is a descendant of the dinosaurs, and diseases of the chicken have been used as a model for the potential diseases that may have affected dinosaurs. At the professional education levels, this book will be very valuable for those studying veterinary medicine and learning about the chicken as the chicken is also the model for other avian species. This book will serve as a resource for those veterinarians and scientists working with the chicken. Hence, it is with great anticipation that I look forward to having this book in my library and adding it to my collection of chicken‐related books. Not only does it provide resources in chicken anatomy and histology, but the book is composed of stunning photography for the chicken aficionado and hobbyist. There is no doubt that this book will be a timeless, valuable global resource for the chicken.
Teresa Y. Morishita, DVM. PhD. Dipl. ACPV
Preface
The domestic chicken, Gallus gallus domesticus, has played an integral role in human history and sustenance for thousands of years. From its origins as wild junglefowl to becoming one of the most widespread and versatile domesticated animals today, chickens have captured the imagination and attention of researchers, breeders, veterinarians, and enthusiasts alike.
This book, “Anatomy and Histology of the Domestic Chicken,” is a comprehensive and meticulously crafted resource that delves into the intricacies of the avian body. Addressing a diverse audience, including veterinary professionals, veterinary students, animal science students, poultry researchers, chicken breeders, and backyard chicken keepers, this work aims to provide a deep understanding of the anatomy, histology, and physiological systems of domestic chicken.
In sixteen meticulously organized chapters, this book covers all major body systems, including the musculoskeletal, respiratory, cardiovascular, digestive, urogenital, and nervous systems. Each chapter is structured to provide a comprehensive overview of the relevant anatomy and histology, coupled with insights into the physiological functions specific to chickens. Additionally, special emphasis has been placed on clinical applications, as understanding the anatomical and histological basis is essential for diagnosing and treating poultry diseases and disorders.
The journey through the avian body does not stop with the mature bird. This book delves into the miraculous world of the egg and chick embryonic development, exploring the fascinating aspects of fertilization and embryology. Understanding the intricate processes of embryonic growth can significantly impact the poultry industry and backyard enthusiasts, optimizing breeding practices, and enhancing the well‐being of these feathered companions.
As our understanding of avian biology continues to evolve, this book seeks to provide readers with the most up‐to‐date information available up to its publication date. We hope that this work serves as a valuable reference, both in the academic realm and practical applications, assisting veterinarians in diagnosing and treating poultry ailments, researchers in pushing the boundaries of avian science, and chicken enthusiasts in raising healthy and thriving flocks.
The development of this book would not have been possible without the contributions of numerous experts in the fields of veterinary anatomy and medicine, and poultry science. Their passion for advancing knowledge in avian anatomy and histology has enriched the contents of this volume.
As we embark on this journey through the anatomy and histology of the domestic chicken, we invite our readers to explore the wonders of avian life, marvel at the intricacies of their anatomy, and embrace the opportunities to enhance the well‐being of these remarkable creatures.
We hope that this book serves as an indispensable guide for all those interested in the fascinating world of domestic chicken, contributing to the advancement of poultry science and the welfare of these cherished birds.
Acknowledgments
We would like to express our gratitude to numerous individuals who have played a vital role in the preparation of this book. We owe a debt of thanks to our colleagues, students, and technical staff, all of whom have contributed significantly to this endeavor.
Our veterinary medicine students have been instrumental in shaping the content of this book. Their inquisitive nature and thoughtful questions during laboratory sessions, particularly in bird cases, encouraged us to delve deeper into the subject matter. We carefully considered their queries while planning each chapter, ensuring that we addressed their concerns.
A special acknowledgment goes to Dr. Teresa Morishita, whose belief in our capabilities led her to involve us in writing two separate chapters: one on Backyard Poultry Medicine and Surgery and another on Gamebird Medicine and Management. Her unwavering support and encouragement were instrumental in our commitment to completing this book.
We are also grateful to the technical staff, led by Kevin Mondragon and his team, at the College of Veterinary Medicine, Western University of Health Sciences. Their expertise in specimen preservation, skeleton preparation, and camera settings greatly facilitated our work, especially during the photography sessions. Their dedication deserves our sincere appreciation.
We extend our heartfelt thanks to all the chapter writers who generously shared their expertise by contributing to this book. Your willingness to share your knowledge is truly commendable.
Dr. Alexandra Gean played a pivotal role in enhancing the readability of several chapters. Her valuable input and organization of paragraphs ensured a smooth transition of information from one topic to the next. Her support and encouragement to this project were contagious. Thanks Ally.
We extend our heartfelt gratitude to Dr. Miguel Saggese for his generous and invaluable contributions to the review of chapters for this book. His expertise and meticulous attention to detail have greatly enriched the quality of our work. We are profoundly thankful for his commitment and collaborative spirit, which have made a significant difference in the success of this book.
We would like to acknowledge the contributions of Wiley's collaborators, who provided invaluable insights that guided our writing process, particularly in the initial chapters. Your assistance saved us time and kept us on track.
Finally, we are grateful to Western University of Health Sciences for their support, financial and logistic. Their continuous encouragement has been instrumental in our efforts to complete this book and make it accessible to all who wish to learn from it.
Lists of Abbreviations
Chapter 2
None
Chapter 2
None
Chapter 3
ATP
adenosine triphosphate
M
muscle
Chapter 4
cm
centimeter
SEM
scanning electron microscope.
Chapter 5
mm
millimeter
μm
micrometer
Chapter 6
JG
juxtaglomerular
MD
macula densa
PAS
periodic acid‐Schiff
Chapter 7
SST
sperm storage tubules
UVJ
utero‐vaginal junction
LMSP
male sperm precedence
LH
luteinizing hormone
OIH
ovulatory‐inducing hormone
GnRH
gonadotropin‐releasing hormone
ZPs
zona pellucida glycoproteins
AR
acrosome reaction
PTX
pertussis toxin
Chapter 8
GH
growth hormone
HPA
hypothalamic‐pituitary‐adrenal
PLP
prolactin‐like protein
IGF1
insulin‐like growth factor‐1
PVN
paraventricular nucleus
POA
preoptic area
ARC
arcuate nucleus
PVNP
araventricular nucleus
SCNS
uprachiasmatic nucleus
TRH
thyrotropin‐releasing hormone
CRH
corticotropin‐releasing hormone
GnRH
gonadotropin‐releasing hormone
FSH
follicle‐stimulating hormone
LH
luteinizing hormone
ACTH
adrenocorticotropic hormone
PRL
prolactin
TSH
prolactin, thyroid‐stimulating
ADH
antidiuretic hormone
MSH
melanocyte‐stimulating hormone
T4
thyroxine
T3
triiodothyronine
PTH
parathyroid hormone
UB
ultimobranchial bodies
Chapter 9
mm
millimeter
HZ
hertz
Chapter 10
AV
atrioventricular node
a
artery
H. & E.
hematoxylin and eosin
Chapter 11
MALT
mucosal associated lymphoid tissues
GALT
gut‐associated lymphoid tissues
Ab
antibody
Ig
immunoglobulin
mRNA
messenger ribonucleic acid
Ig
immunoglobulin
M cell
microfold cell
MHC
major histocompatibility complex
PALS
periarterial sheaths
PELS
peri‐ellipsoidal lymphocytes sheaths
CALT
conjunctival associated lymphoid tissue
MALT
mucosal‐associated lymphoid tissue
BALT
bronchiole‐associated lymphoid tissue
Chapter 12
CNS
central nervous system
PNS
peripheral nervous system
CSF
cerebrospinal fluid
L2
lumbar 2
L3
lumbar 3
L4
lumbar 4
S1
sacral 1
S2
sacral 2
Chapter 13
PCR
polymerase chain reaction
gm
gram
Chapter 14
LED
a light‐emitting diode
spp
species
Chapter 15
None
Chapter 16
SST
sperm storage tubules
UVJ
utero‐vaginal junction
LMSP
last male sperm precedence
OIH
ovulatory‐inducing hormone
ZP
zona pellucida
AR
acrosome reaction
PTX
pertussis toxin
1External Features of Chicken
Wael Khamas and Josep Rutllant
College of Veterinary Medicine, Western University of Health Sciences, Pomona, CA, USA
1.1 Skin
The chicken skin is thin, loosely attached to the hypodermis, and in most bird species, it has pale pink or bluish pink color. In some species, it can be yellow and even blackish colored based on the presence of xanthin, carotenes, and melanocytes. When compared to mammals, the avian skin is, for most species, dry, often translucent, and inelastic over most of the body, which makes it prone to tears (Nett and Tully 2003). As an additional adaptation for flying, the bird loosely fits inside its skin over most of the body. In some regions, it is strongly attached to the underlying tissue with little or no modification with a very small dermis, like in the skull and the wing tips.
The integument is highly modified on the beak, feet, and certain parts of the bird body such as the ornaments (wattles and crest). The avian skin is the largest organ and acts as the first line of defense against pathogens. It is also involved in heat regulation and prevents the loss of body fluids. It is the largest sensory organ in the body, having receptors for temperature, pain, pressure, and tactile discriminations (Lucas and Stettenheim 1972, p. 1975, pp. 485–486).
The skin has two main types of keratins: (i) soft keratin, which is present in the body and ornaments (alpha keratin) and (ii) hard keratin, found on the scales, spurs, beak, and feathers (beta keratin) (Greenwold et al. 2014). Both male and female may develop thickened areas within the dermis on the ventral abdominal region corresponding with the brooding or incubation patches.
Most of the skin is covered with feathers and no glands are present except for the aural, third eyelid, vent, and uropygial regions. The absence of sweat glands indicates that birds thermoregulate by panting and gular fluttering, among other mechanisms and behaviors. The thick coat of feathers limits the exchange of heat with the environment, a significant difference with mammal's skin. In certain regions of the chicken body, the epidermal cells of the skin produce a holocrine lipidic secretion, such as in the rictus, interdigital web, and in the uropygial gland (Menon et al. 1981).
The chicken skin is divided into the external epidermis and the deeper dermis that is anchored to the underlying hypodermis.
1.1.1 Epidermis
The epidermis is thin in feathered regions and thick in bare regions. The epidermis is composed of stratified squamous epithelium; the number of layers varies depending on the body region. The epidermis, except in the comb and wattle, is mostly composed of different strata (singular stratum): germinativum or basale, spinosum, granulosum, lucidum, and corneum. Not all layers/strata described in mammals are present in the epidermis of the thin skin of the chicken like the stratum lucidum. The avian epidermis is composed of one to six layers of epithelial cells depending on the body region. This includes the basal (germinal) layer, composed of simple cuboidal cells, an intermediate section of several layers composed of cuboidal cells (stratum spinosum), and the stratum corneum, composed of flattened cells without nuclei. The stratum corneum varies in thickness from region to region (Figure 1.1A and B).
Figure 1.1 (A and B) Histology sections of abdominal chicken skin. This extremely thin skin layer shows (a) slightly keratinized stratified squamous epithelium, (b) dermis, (c) blood vessels. (A) H&E and (B) trichrome stains.
1.1.2 Dermis
The dermis consists of irregular connective tissue of variable thickness between the subepithelial region to the deep dermis close to the hypodermal layer and adipose tissue. Three layers can be identified, the stratum superficialis being the more superficial, and consisting of irregular connective tissue with low innervation and in close contact with the stratum basale of the epidermis. A deeper layer, the stratum profundum, on the contrary, is richly innervated, and can be subdivided into two distinct regions or sublayers, the stratum compactum and the stratum laxum. The stratum compactum by name is a thick irregular connective tissue rich in collagen and with a small number of elastic fibers. This layer is filled with blood vessels of variable sizes and with bundles of nerve fibers. The stratum laxum consists of loosely arranged connective tissue, smooth muscle, and abundant adipose tissue. Homberger and Silva (2000) reported that the fat deposits in the stratum compactum and stratum laxum of the avian skin act as a non‐compressible hydraulic tissue for the movement of feathers inside the dermis. This region mostly harbors contour feathers which are seen surrounded by a layer of collagen fibers (Bharathi et al. 2018).
1.1.3 Hypodermis (Subcutis)
The hypodermis, subcutis, or subcutaneous layer underlays the dermis, but it is not considered part of the skin. It consists of a layer of connective tissue rich in collagen bundles but with few elastic fibers. It is highly vascularized, innervated, and has lymphatic drainage. In gross anatomy, this layer is the superficial fascia and can be divided into three different layers: (i) the superficial layer, which is immediately below the dermis, (ii) a middle layer that may have adipocytes and called panniculus adiposus in mammals which extends in between skeletal muscles (intermuscular fascia), and (iii) the deeper layer or fascia, located between the skeletal muscles and the bone, and blending with the periosteum.
1.1.4 Blood Supply of the Skin and Nerve Ending
The blood supply to the chicken skin derives from larger blood vessels present in the hypodermis that branch into smaller arteries and arterioles when they penetrate the dermis. Blood capillaries branch from them to reach the subepithelial region, directly supplying blood to the upper portion of the dermis and the epithelium through diffusion. Certain regions of the skin and its associated structures, such as the ornaments, comb, wattle, and ear lobes, are highly vascularized.
Arteries and veins are usually accompanied by nerve fibers. Mechanoreceptors in the skin correspond to the mammalian Vater Pacini (Pacinian) corpuscle, called Herbst corpuscles in birds. They are present in the feathered skin, beak, and distal leg (Hodges 1974, pp. 11–12). The small type Herbst corpuscles are usually superficially located closer to the feather bulbs while the larger ones are localized deep in the dermis. These encapsulated structures are composed of an inner bulb surrounded by several layers of loose connective tissue. Another corpuscle, described by Gottschaldt (1985) is the Grandry corpuscle, equivalent to the Meissner corpuscles in mammals, present in the beak skin of geese and ducks that respond rapidly to active movement in aquatic environments.
1.2 Structures Associated with the Skin
1.2.1 Patagium (pl. patagia)
The patagia are thin, feathered membranous folds of skin that connect the humeral bone and shoulder with the distal ulna/radius and the carpus that sits along the cranial border of the wing. The cervical extension of the patagium (referred to as parapatagium), present in front of the shoulder joint which is not part of the wing. The patagium is composed of four parts (prepatagium, metapatagium, postpatagium and alular patagium). The main patagium of the wing is the prepatagium (wing web), between the shoulder and the carpus. This prepatagium is rich in elastic connective tissue which enables the chicken to hold the wings close to the body without muscular effort. The free prepatagium is a triangular fold or thin double fold of skin laying between the radius and ulna and the humerus. The thin free edge of the prepatagium is directed anteriorly (Lucas and Stettenheim 1972, p. 57). The metapatagium is also triangular, a very small fold of skin located between the thorax and the wing. Its edge attached to the wing along the caudal border of the triceps humeralis muscle. The postpatagium is a chevron‐shaped skin web that lies caudal to the forewing and the carpal/metacarpal bones, extends from the elbow to the longest digit, and bears the primary and the secondary remiges. The alular patagium is a small web that lies between the adductor indicis muscle (Hudson and Lanzillotti 1972, p. 43) and the tendon to digit III. Its free edge directed toward the tip of the wing (Lucas and Stettenheim 1972, p. 57).
1.2.2 Operculum
The operculum is a cover or a lid present dorsal to the anterior nares (nasal openings) of a bird at the base of the beak (Figure 1.2). The shape and structure may vary from one breed to another.
1.2.3 Ornaments
1.2.3.1 Comb
The most distinctive skin protuberance in the head of the chicken is the comb. Its shape varies among different breeds of chicken. It could be a single crested, rose, pea shaped, or strawberry type of comb depending on the breed. Rooster’s combs are always bigger than that of a hen. In poultry production, the comb’s size and color are used as features to determine the health and egg production status of the hens. The comb size is related to androgen levels in the male, and this may be associated with the degree of aggressiveness and dominance behavior in both male and female (Candyland 1969). One of the main functions of the comb is to assist in thermoregulation by absorbing light and contributes to the social communication and structure of the flock. The comb is an essential feature to help identify individual animals. Color breed variations reflect also on the color of chicken comb. Fölsch et al. (1994) compared the crest size of Hisex white hens with Hisex brown hens and observed larger and paler combs in white hens compared with brown hens. They stated that this tendency is clearer under artificial light conditions, less light, and higher temperature of the environment in chickens housed in battery cage systems. The comb epidermis has a thin keratinized stratified squamous epithelium. A single basal cuboidal layer (stratum basale) and two to three intermediate layers (stratum intermedium) correspond to the mammalian spinosum layer in young birds that increase in number in adult birds. The superficial layer is flattened squamous epithelial cells located below the stratum corneum. The dermis has a stratum superficialis, which is an irregular connective tissue highly vascularized, with arterioles, venules, and capillaries situated close to the stratum basale. The stratum profundum also has two sublayers: the stratum compactum and the stratum laxum. The stratum compactum is composed of thick, irregular connective tissue rich with collagen but with little elastic fibers. This stratum is filled with medium and small muscular arteries, arterioles, and capillaries, accompanied by bundles of nerve fibers. The glomera of arterioles (a group of arterioles branching and anastomosing with epithelioid cells) are present at the junction of the stratum compactum with the stratum laxum. The presence of these arterioles acts to reduce the need for heat production when oxygen is low (O’Dea 1990). Therefore, keeping the comb warm does not put burden on the blood circulation. The stratum laxum separates the skin from both the hypodermis and the skeletal muscles. It has less connective tissue fibers with larger blood vessels embedded within white adipose tissue. Chicken comb is reported to be rich in hyaluronic acid, which can be used in human medicine for joint lubrication (Almond 2007) (Figures 1.2 and 1.3).
Figure 1.2 Female (A) and male (B) head external features. (a) Single comb, (b) wattle, (c) ear lobe, (d) tomium, (e) culmen, (f) operculum, (g) external nares (nasal opening), (h) maxillary rictus, (i) mandibular rictus, (j) superior eyelid, (k) inferior eyelid, (l) third eyelid (nictitating membrane), and (m) aural feathers.
1.2.3.2 Wattle
The wattles are an elongated extension or flap of featherless skin below the head and on both sides of the head. The wattle size and shape vary from breed to breed as the comb does. In general, it is larger in males compared to females, becoming even larger in older males. It is highly vascularized, which results in typical red coloration of the comb. Both wattle and comb become congested during mating season because of the high vascularity in the subcutis which results in increasing the rigidity and in the intense color of these structures (Nickel et al. 1977, p. 159). The skin of the wattle is composed of epidermis and dermis. The epidermis is thin keratinized stratified squamous epithelium of five to six cell layers. The basal layer (stratum basale) is simple columnar followed by two to three cuboidal layers of middle layer (stratum intermedium). The outermost layer is simple squamous flattened cells below the thin keratinized layer (stratum corneum). The dermis has a more superficial layer which is highly vascularized (arterioles, venules, and capillaries) close to the stratum basale and a thinner connective tissue with blood vessels and nerve fibers. The dermis of the wattle is a thin loose connective tissue filled with blood vessels and nerve fibers (Figures 1.2 and 1.4).
1.2.3.3 Ear Lobes
The earlobes are featherless skin extending down below the external ear openings. It is usually red in color because of the presence of extensive blood supply (capillaries and venous sinuses) which are present immediately under the epidermis (Figure 1.2). Though, in certain breeds, they could be white. The color of the earlobe usually is correlated with the color of eggs in laying hens. Chickens with red earlobes tend to lay brown eggs while those with white earlobes tend to lay white eggs (Morishita et al. 2021, p. 464). The ear lobe is covered by keratinized stratified squamous epithelium of five to six layers total thickness. These cells are two to three cuboidal cell layers and two to three flatted squamous superficial cells. The dermis forms a highly vascularized dense irregular connective tissue below the epithelium. Deeper, the dermis is less dense than the superficial layer with the presence of elastic fibers and large blood vessels. Resident macrophages (histiocytes) are present in addition to the regularly present fibroblast/fibrocyte. Elastic fibers and variable amount of connective tissue density were observed by the authors depending on the sectioned region of the ear lobe. The epithelial layer thickness of the ear lobe increases along the attachment side to the head. Herbst corpuscle close to the feather’s follicle is small, while deeper corpuscles are larger.
Figure 1.3 Comb of young (A) and adult rooster (B) showing keratinized stratified squamous epithelium with higher number of stratifications of cells within the epidermis (a), dense irregular connective tissue of the dermis (b). H&E stain.
Figure 1.4 Wattle of a rooster showing thin keratinized stratified squamous epithelium (a), highly vascularized upper layer of the dermis (b), thin loose connective tissue from middle layer of the dermis (c), and deeper layer of the dermis (d). Trichrome stain.
1.2.3.4 External Ear Opening
The external ear canal opening of the chicken is caudal to the quadrate bone. Auricular glands are present on the ventral wall of the canal. These glands open into a duct and can be visualized under higher magnification (König et al. 2016, p. 243). Aural sebaceous glands around the external ear secrete a waxy substance (Menon and Salinukul 1989). Six classes of neutral lipids are identified by thin layer chromatography of the lipid materials extracted separately from the secretion as well as from the isolated whole glands present in the skin of the floor of the external ear canal of the domestic fowl (Dutta et al. 1997).
1.3 Feathers
Feathers are important structures and perform several functions during the bird lifetime including flight, thermoregulation, water repellent, communication, water transport, transfer of plant seeds, sound production, and brooding (incubation of eggs) (Lucas and Stettenheim 1972, pp. 257, 276).
1.3.1 Development
The somatopleure (ectoderm and somatic mesoderm) expansion and closure leads to the juxtaposition of the ventral pteryla. The embryonic proximal somatopleural mesoderm is destined to form a feather‐forming dermis at two days of incubation (Fliniaux et al. 2004). Other researchers stated that early development of the feathers from pterylae start at day six of incubation of having a dermal pulp (sheath and basal layers) (Prum and Dyke 2003). Epidermal placode elongates forming a short bud with a tubular central dermal tissue. The epidermis forms the barb ridges and barbs of the first natal down. The pulp starts from the germ cells to produce the entire feather. Feathers are replaced/renewed throughout the entire life of the bird in a sequence of (continue for most species) events called molt. Feathers are entirely epidermal in origin and lined with epidermal cells which are anchored inside the dermis after passing through the epidermis and sometimes the hypodermis. Prum and Brush (2002) stated that a feather follicle differs from a hair follicle in that the follicular invagination is not merely a depression in the epidermis but a circular trough that encircles a persistent dermal papilla. Both primary and secondary feathers attach close to the periosteal layer of the bones.
1.3.2 Description of Feathers
Feathers are skin appendages like the glands of mammalian skin. They are tubular and widely variable in shape and chemical composition of the arrangement and numbers of keratinocytes (Prum and Dyke 2003) depending on their location and/or function. Morphologically, feathers are considered homologous of reptilian scales. However, in development, morphogenesis, gene structure, protein shape, sequence, filament formation and structure, feathers are different from scales (Brush 1996).
Researchers have noted the role of feathers in repelling parasites alone or in conjunction to earth elements. In a study conducted by Martin and Mullens (2012), they permitted chickens infested with lice to apply sand, litter, or kaolin (a fine clay) to their feathers for dusting. The use of kaolin resulted in significant reductions in lice populations, whereas dusting with sand or litter had little to no effect. Likewise, Vezzoli et al. (2015) reported that dusting with sand showed no impact on ectoparasitic mites.
1.3.3 Ptilosis and Pterylosis
Ptilosis refers to the complete set of feathers (plumage) associated with the feather’s follicles, while pterylosis is the arrangement of feathers within certain tracts over the bird skin. On one plucked adult rooster (the authors prepared), different tracts including ventral and dorsal views were labeled (Figure 1.5A–C). The term pteria is a part of the bird skin where feathers grow, while apteria is the naked spaces between feathered skin, for example, on both sides of the chicken neck. Detailed feather tracts (pterylosis) of the chicken are described by Lucas and Stettenheim 1972, pp. 74–75).
Figure 1.5 (A) Ventral view of a plucked adult rooster. (a) Lateral cervical tract, (b) pectoral tract, (c) sternal tract, (d) pectoral apterium, (e) sternal apterium, (f) secondary coverts, (g) secondary feathers, and (h) crural tract. (B) Ventral view of plucked adult male chicken. (a) Pectoral tract, (b) pectoral apterium, (c) sternal apterium, (d) sternal tract, (e) abdominal tract, (f) abdominal apterium, and (g) anal circulet. (C) Dorsal view of a plucked adult male chicken. (a) Dorsal cervical tract, (b) lateral cervical apterium, (c) interscapular tract, (d) scapular apterium, (e) humeral tract, (f) post humeral tract, (g) upper secondary feathers, (h) primary feathers, (i) dorsopelvic tract, (j) dorsal caudal tract, and (k) crural tract.
1.3.4 Feathers Color
Feathers can be of any color or mix of colors. However, color, structure, and shape may vary after molting. Melanin is a common pigment in chicken skin. Melanin is produced by melanocytes (a neural crest cell in origin). These cells are situated at the basement membrane of the skin and have pseudopodia to extend between the keratinocytes (all epidermal cells) of the epidermis. Through the process of transcellular movements, the melanosomes (melanin pigment within a single layer membrane) are phagocytosed by the keratinocytes (Sharlow et al. 2000). The second most common pigment is the carotenoid, a large group of pigments produced by plants and other organisms. Once absorbed, carotenoids are transported in fat globules through the blood to the dermal feather pulp where they are selectively absorbed by the keratinocytes (Brush 1978). Red coloration comes from carotenoids, yellow from either carotenoid or melanin, while pink is a mixture of both red and yellow. If melanin pigments reach the epidermis in substantial amounts, these black pigments result in darkening the entire skin of the chicken, like in Silkie chickens. Green color comes from the lipochrome in the epidermis and melanin in the dermis. Other colors result from the combination of different pigments and physical properties of the feathers (Getty 1975, pp. 2071–2081).
