Chicken Anatomy: Labeled Diagrams and Interactive 3D Model

A chicken is a bird built for walking, scratching and short bursts of flight. On the outside it has a fleshy comb and wattles, a horny beak with no teeth, feathers in distinct regions, and bare, scaly legs with four toes. Inside it has a crop to store food, a two-part stomach (the glandular proventriculus and the grinding gizzard), two long caeca, small fixed lungs ventilated by nine air sacs (some texts count eight), a four-chambered heart, kidneys but no bladder, and a single cloaca that ends at the vent.

This page describes the domestic chicken, Gallus gallus domesticus, using a laying hen as the reference animal, with notes on the rooster. Breeds differ in comb type, plumage, size, earlobe colour and even toe number, so where those differences matter they are pointed out.

Directions: cranial means towards the beak, caudal towards the tail, dorsal the back and ventral the belly and keel. Left and right are always the bird's own. Most diagrams, including the ones here, show the left side, because that is where the hen's ovary and oviduct lie.

The external anatomy of a chicken includes the comb, beak, nostrils, eyes, ear openings, earlobes and wattles on the head; the hackles and cape on the neck; the back, saddle, breast and abdomen on the body; the wing coverts, secondaries and primaries on the wing; the tail feathers and preen gland; the vent; and the thigh, drumstick, hock, shank, spur, toes and claws on the leg.

Two features cause the most confusion. First, the backward-bending joint at the bottom of the feathered leg is the hock, the bird's ankle; the knee is hidden under the body feathers. Second, the "claw" that some farm guides mention is the hind toe (the hallux), while the nails at the ends of all the toes are the claws proper.

The skin itself is thin and has almost no glands. Poultry Hub lists only two kinds: the preen (uropygial) gland at the base of the tail and the glands of the outer ear canal. Chickens have no sweat glands; they shed heat by panting, by holding the wings away from the body and through the blood-rich comb and wattles.

External anatomy is what you can see and feel on a live bird: feathers, comb, beak, legs and vent. Internal anatomy is everything under the skin: the skeleton, muscles and organs. A few internal structures can be felt from outside, which is how poultry keepers check a bird's health.

The head carries the comb on top, the wattles below the beak, an earlobe and an ear opening on each side, two large eyes and the beak with its two nostrils. Inside, a light skull with huge eye sockets protects a small brain.

• Comb: A sexual ornament that signals maturity and health, and a heat radiator: its rich blood supply lets the bird lose heat.
• Wattles: Like the comb, they are an ornament for display and help shed heat.
• Earlobes: A breed and display feature; it has no role in hearing.
• Ear opening: Lets sound into the ear canal and onto the eardrum.
• Eye: Vision. The side-facing eyes give a very wide field of view for spotting predators.
• Nostrils: Air enters here for breathing and smelling. A flap (operculum) partly covers each nostril and keeps out dust.
• Beak: Picks up food, pecks, tears and preens. Chickens have no teeth, so the beak does not chew.

Earlobes are red in many breeds and white in Mediterranean breeds such as the Leghorn. White-lobed breeds often lay white eggs and red-lobed breeds brown eggs, but that is only a rule of thumb, with exceptions.

Yes. A chicken's eye is kept moist by a small lacrimal gland and a large Harderian gland, and tears drain away through a duct. Poultry Hub describes the tears draining into a collecting sac and then, through a special duct, into the nasal cavity, in the same general way as the human nasolacrimal duct.

Each eye has an upper and a lower eyelid plus a third eyelid, the nictitating membrane, which sweeps across the eye to clean it. The Harderian gland, behind the eyeball, lubricates this third eyelid and is also an immune organ: Poultry Hub lists it among the places that receive antibody-making B-cells. Because tears drain into the nose, eye and nasal problems in chickens often appear together.

• Tear glands & duct: The Harderian gland lubricates the third eyelid and is also an immune organ; the duct drains tears into the nose.
• Eyeball & pecten: Forms images. Like most birds, chickens see colour well.
• Scleral ring: Stiffens the large eye and helps hold its shape.

A chicken's mouth has no teeth and no soft palate, so the mouth and throat form one cavity, the oropharynx. The roof has a long slit, the choana, that opens into the nasal cavity. The narrow, arrow-shaped tongue has backward-pointing barbs, and behind it sits the raised slit of the glottis, the entrance to the windpipe.

• Tongue: Moves food and water to the back of the mouth to be swallowed.
• Mouth & pharynx: Takes in food, moistens it with saliva, and passes it to the oesophagus.
• Larynx & glottis: Closes the airway during swallowing.

Poultry Hub notes that the palate has five rows of backward-pointing papillae and that taste buds sit mainly at the base of the tongue and on the floor of the mouth. The larynx has no vocal cords and no epiglottis. The chicken's voice comes from the syrinx, deep in the chest.

Inside a laying hen, the crop sits at the base of the neck; the heart lies just behind it, cradled by the two lobes of the liver; the proventriculus and gizzard lie behind the liver; the intestines fill the right and lower abdomen; the left ovary and the long oviduct fill the left abdomen; and the lungs and kidneys are pressed against the backbone. Thin air sacs (nine in most poultry references) fill the spaces between the organs.

This is the text version of the 3D model: every labeled structure of the chicken, grouped by body system, with what it does.

Food passes from the beak through the oesophagus to the crop, on to the proventriculus (glandular stomach) and the gizzard (muscular stomach), then through the duodenum, jejunum and ileum. Undigested material goes through the short colon, and some enters the two caeca. Everything ends in the cloaca and leaves through the vent.

Poultry Hub gives these sizes for an adult chicken: a duodenal loop of about 20 cm, about 120 cm of jejunum and ileum together, and two caeca of 16–18 cm each. A meal takes about 4 hours to pass through a young bird, about 8 hours in a laying hen and about 12 hours in a broody hen.

The crop (ingluvies) is a stretchy pouch of the oesophagus just before it enters the chest, at the base of the neck in front of the wishbone. It stores food so that a chicken can eat quickly and digest later. Very little digestion happens there, although some grain ferments.

A full crop is easy to feel as a soft lump at the front of the breast in the evening. It should be empty by the next morning. A crop that stays hard or full points to a blockage (impacted crop), and a sour-smelling, squashy crop to a yeast infection (sour crop).

The gizzard (ventriculus) is the chicken's grinding stomach: a thick, disc-shaped organ made of two pairs of strong muscles, lined by a tough, yellowish layer called koilin. With swallowed grit, it crushes whole grains, doing the job that teeth do in mammals.

It works as a team with the proventriculus, the spindle-shaped glandular stomach in front of it. The proventriculus secretes hydrochloric acid and pepsinogen, but food passes through it quickly; most acid digestion happens in the gizzard, and food can move back and forth between the two. A cooked gizzard, sold as a giblet, still shows the shiny tendon sheet (tendinous centre) on each side and the peeled-away koilin lining.

• Proventriculus: Secretes hydrochloric acid and pepsinogen, which start protein digestion.
• Gizzard: Grinds food mechanically, doing the job teeth do in mammals.
• Duodenum: Receives bile and pancreatic juice; most digestion and absorption begins here.
• Pancreas: Makes digestive enzymes (for protein, fat and starch) and the hormones insulin and glucagon.
• Caeca: Bacteria ferment fibre, reabsorb water and make some B vitamins.
• Meckel's diverticulum: In the embryo and newly hatched chick it carried yolk into the gut; in adults it contains lymphoid tissue.

The liver is the largest gland in the chicken: a dark red-brown organ with a right and a left lobe that wrap around the heart, lying just above the sternum. Poultry Hub gives its weight as about 50 g in an adult bird. Two bile ducts leave the right lobe, and the green gallbladder sits on that lobe.

In a laying hen the liver has an extra job: under the influence of estrogen it makes the proteins and fats of the egg yolk and sends them to the ovary in the blood. A chick's liver looks pale yellow for its first 10–14 days because it is full of absorbed yolk fat.

A chicken has one cone-shaped heart with four chambers: two atria and two ventricles. It lies low in the chest, in the midline just behind the crop, with its tip tucked between the liver lobes. The right side pumps blood to the lungs and the left side to the body, as in mammals.

Two details are bird-specific. The valve between the right atrium and right ventricle is a strong muscular flap rather than a thin, three-cusped valve, and the aorta curves to the right, not the left, as it leaves the heart. Poultry Hub describes the bird heart as relatively large for the body size.

• Heart: Pumps blood in two circuits: the right side to the lungs, the left side to the body.
• Aorta: Carries oxygen-rich blood to the body.
• Brachiocephalic arteries: Each divides into a carotid artery to the head and a large artery to the wing and breast muscles.
• Jugular veins: Drain blood from the head into the cranial venae cavae.
• Caudal vena cava: Returns oxygen-poor blood from the legs, kidneys and organs.

Chickens breathe with two small lungs that do not inflate, plus air sacs that act as bellows. Poultry Hub counts nine: one clavicular air sac (which holds the syrinx) and pairs of cervical, cranial thoracic, caudal thoracic and abdominal air sacs; the University of Kentucky also counts nine. Some anatomy texts count eight, because they treat sacs that are joined across the midline as a single sac. Air flows through the lungs in one direction, during both breathing in and breathing out.

The trachea is 15–18 cm long in a medium-sized adult, with about 108–125 complete cartilage rings. It ends at the syrinx, the voice box that makes the rooster's crow. Some air sacs extend into bones: the clavicular air sac enters the humerus, making it pneumatic (air-filled).

• Trachea: Carries air between the throat and the lungs.
• Syrinx: Makes the crow, clucks and alarm calls: vibrating membranes in its wall produce the sound.
• Lungs: Gas exchange. Air flows through tiny tubes (parabronchi) in one direction, during both breathing in and out.
• Cervical air sacs: Part of the bellows system that moves air through the lungs; they extend into the vertebrae.
• Clavicular air sac: Bellows for the lungs; its extension into the humerus makes that bone pneumatic.
• Thoracic air sacs: The cranial pair fills with air that has passed through the lungs; the caudal pair with fresh air on its way to the lungs.
• Abdominal air sacs: Hold fresh air that is pushed through the lungs when the bird breathes out.

The chicken skeleton is light but rigid. Many bones are fused: the hand bones, the shin and ankle bones, the back vertebrae into the notarium and synsacrum, and the tail tip into the pygostyle. The breastbone has a deep keel for the flight muscles, and the collarbones are fused into the wishbone (furcula).

Pneumatic bones, according to the University of Kentucky's extension article, include the skull, humerus, clavicle, keel, pelvic girdle and the lumbar and sacral vertebrae. The leg bones are not air-filled in the same way; in laying hens their marrow cavities fill with medullary bone instead.

A chicken wing has the same bones as your arm, reduced and partly fused: the humerus in the upper wing, the radius and ulna in the forearm, and a fused hand (the carpometacarpus) with three small digits. Ten primary flight feathers grow from the hand and the secondaries grow from the ulna. Coverts overlap their bases.

US poultry rules define the wing drummette as the humerus of the wing with its skin and meat, and the wing portion as the rest of the wing once the drummette is removed. When the wing is folded, the forearm and hand lie back along the body and the primaries tuck under the secondaries, so only the coverts, the triangular wing bay and the primary tips are visible.

• Humerus: Transmits the force of the breast muscles to the wing.
• Radius: Works with the ulna to extend and fold the wing.
• Ulna: Anchors the secondary flight feathers; small bumps on the bone (quill knobs) mark their attachment.
• Carpometacarpus: Carries the primary feathers.
• Wing digits: Support the outer primaries and the alula, which smooths airflow at low speeds.
• Primary feathers: Provide thrust in flight. Chickens fly only short distances, in bursts.
• Secondary feathers: Form the lifting inner part of the wing in flight.

A chicken leg has three long segments: the thigh (femur), the drumstick (tibiotarsus with the thin fibula) and the bare, scaly shank (tarsometatarsus), ending in four toes. The bird stands on its toes with the ankle (hock) high off the ground, and the knee is tucked up under the body feathers.

• Thigh: Contains the thigh muscles (dark meat) that swing the leg.
• Drumstick (lower thigh): Contains the large calf muscles that extend the foot.
• Hock: It is the bird's ankle, not its knee. It bends the opposite way to a human knee because it is a different joint.
• Shank: Carries the bird's weight. The scales protect it.
• Spur: A weapon used in fights between roosters.
• Toes: Spread the bird's weight, grip perches and scratch the ground for food.
• Claws: Scratching and gripping.

The shank and the tops of the toes are covered with keratin scales attached to the skin, which Poultry Hub describes as a carry-over from the chicken's reptile-like ancestors. Spurs grow on the back of the shank from a bony core; they are much larger in roosters, especially older ones. Breeds such as the Dorking, Silkie, Houdan and Faverolles have a fifth toe.

Chicken meat is muscle, so every supermarket cut maps onto real anatomy. White meat comes from the breast and wing drumette, whose fibres are mostly fast white fibres with little myoglobin. Dark meat comes from the thigh and drumstick, which have more red fibres for sustained work such as walking.

US rules separate drumsticks from thighs by a cut through the knee joint, take thighs off at the hip joint (they may include pelvic meat), and define a leg as the thigh and drumstick together. The tough white strands in a drumstick are tendons running down to the foot.

• Pectoralis: Pulls the wing down: the power stroke of flight.
• Thigh muscles: Swing the leg forward and back and straighten the knee for walking, scratching and perching.
• Drumstick muscles: The gastrocnemius extends the foot at the hock; the long flexor tendons curl the toes.
• Wing muscles: The biceps bends the elbow and folds the wing; the triceps straightens it.

The chicken tenderloin is the supracoracoideus, the deep breast muscle that lies alongside the keel underneath the main breast muscle. The meat trade often calls it the "pectoralis minor", but it is not the same muscle as the human pectoralis minor, and veterinary sources name it the supracoracoideus or deep pectoral muscle.

Its job is surprising: although it sits below the wing, it raises the wing. Its tendon runs up through the triosseal canal, a gap between the coracoid, scapula and furcula, and hooks over the top of the humerus like a rope over a pulley. The pectoralis on top of it pulls the wing down. Because the tenderloin sits in a tight compartment, its blood supply can fail in heavy broilers, causing deep pectoral myopathy (green muscle disease).

• Supracoracoideus: Raises the wing. Its tendon runs up through the triosseal canal at the shoulder and over the top of the humerus like a rope over a pulley.

A hen has a single working ovary and oviduct, both on the left; the right ones regress during embryonic development and do not work in the adult. A rooster has two bean-shaped testes inside the body, against the backbone near the kidneys, and two sperm ducts that open into the cloaca. Neither sex has external genitals.

Poultry Hub gives the active oviduct a length of about 70–80 cm, and US extension sources about 25–27 inches. Day-old chicks can be sexed by looking for the rudimentary male organ in the everted vent, a method developed in Japan, or by wing feathers and down colour in certain crosses.

• Ovary: Grows yolks and releases one at a time (ovulation); makes estrogen.
• Testes: Make sperm and testosterone.
• Ductus deferens: Carries and stores sperm; it is the main sperm store in the rooster.
• Papillae & phallus: Roosters have no penis: sperm passes from the papillae to the hen's cloaca when the vents touch.

A hen takes about 25–26 hours to turn a yolk into a laid egg (often rounded to "about a day"). The yolk is released from the ovary, caught by the infundibulum, and then coated in turn with egg white, shell membranes and shell as it moves down the oviduct.

1. Ovulation. A mature yolk, up to about 40 mm across, splits out of its follicle along the stigma. The next yolk is usually released within about an hour after the previous egg is laid.
2. Infundibulum (about 15–17 minutes). The muscular funnel moves to engulf the yolk. If sperm are present, fertilisation happens here.
3. Magnum (about 3 hours). Glands add the thick albumen.
4. Isthmus (about 75 minutes). The inner and outer shell membranes are added and the egg takes its shape.
5. Shell gland (20 hours or more). Water and salts plump up the albumen, then the calcium carbonate shell is laid down. Brown pigment is added in the last hours.
6. Vagina and vent. The egg enters the vagina small end first, turns, and is pushed out through the cloaca, usually blunt (large) end first.

Because the cycle is a little longer than a day, each egg in a clutch is laid a little later in the day. The University of Kentucky's extension article notes that hens almost never ovulate after about 3 p.m., so a hen that laid late in the day may skip a day before starting a new clutch. An egg needs no rooster: an unfertilised egg is laid in exactly the same way.

• Infundibulum: Captures the yolk; fertilisation happens here if sperm are present. The yolk stays about 15–17 minutes.
• Magnum: Adds about half of the egg white (albumen), mainly the thick albumen, in about 3 hours.
• Isthmus: Adds the inner and outer shell membranes and a little albumen, and sets the egg's shape (about 75 minutes).
• Shell gland: First adds water and salts to the albumen ('plumping'), then lays down the calcium carbonate shell, the pigment and the cuticle.
• Vagina: Pushes the finished egg out during laying, and stores sperm in small glands near its junction with the shell gland.

A chicken egg has, from outside in: the cuticle (bloom), the porous calcium-carbonate shell, the outer and inner shell membranes, the air cell at the blunt end, layers of thin and thick albumen (egg white), two twisted chalazae, and the yolk wrapped in the vitelline membrane, with the pale germinal disc on top.

By weight, a fresh egg is roughly 32% yolk, 58% albumen and 10% shell, according to the egg-quality handbook published by the Queensland Department of Primary Industries; Poultry Hub gives ranges of 32–35% yolk, 52–58% albumen and 9–14% shell. Mississippi State University Extension notes that the air cell grows as an egg ages, so a small air cell is a sign of a fresh egg, and that a chick pierces the air cell to take its first breaths before hatching.

The cloaca is the shared chamber at the end of the digestive, urinary and reproductive tracts, and the vent is its opening under the tail. It has three compartments: the coprodeum receives faeces from the colon, the urodeum receives urine from the ureters and the oviduct or sperm ducts, and the proctodeum opens at the vent.

Chickens have no urinary bladder. Their kidneys excrete nitrogen as uric acid, which reaches the cloaca as a thick white paste: the white cap on a chicken dropping. Poultry Hub notes that urine can be moved back into the colon by reverse peristalsis so that water is reabsorbed. The bursa of Fabricius, an immune organ of young birds, opens into the dorsal wall of the proctodeum.

• Cloaca: The coprodeum receives faeces, the urodeum receives urine and the oviduct or sperm ducts, and the proctodeum opens at the vent.
• Vent: The exit of the cloaca. Mating is a brief 'cloacal kiss' in which the vents of rooster and hen touch.
• Kidneys: Filter the blood and remove nitrogen waste as uric acid.
• Ureters: Carry thick, pasty urine full of uric acid.
• Bursa of Fabricius: Trains B-cells, the white blood cells that make antibodies. B-cells were discovered through this organ.

Chicken skin has three layers, the epidermis, dermis and hypodermis, and is thin and loose. Feathers grow only from feather tracts called pterylae, separated by bare strips called apteria, which is why a plucked chicken shows rows of follicles. Poultry Hub lists five feather types in chickens: contour feathers, plumules, filoplumes, chick down and bristles.

The preen gland on top of the tail base secretes oil that the bird spreads over its feathers. Moult, the yearly replacement of feathers, usually happens in autumn, and males moult before females.

The chicken brain has smooth cerebral hemispheres at the front, large optic lobes on the sides of the midbrain, a ridged cerebellum at the back, small olfactory bulbs and a brainstem that joins the spinal cord. Poultry Hub describes the optic lobes as very large compared with those of other species, which fits an animal that relies mainly on sight.

• Cerebrum: Controls learning, behaviour, feeding and social recognition (pecking order).
• Optic lobes: Process vision.
• Cerebellum: Coordinates balance, posture and movement.
• Olfactory bulbs: Process smell.
• Brainstem: Controls breathing and heart rate.
• Spinal cord: Carries messages between brain and body and controls reflexes.
• Sciatic nerve: Carries motor and sensory signals for most of the leg below the hip.

Chickens have eyes on the sides of the head, giving a wide field of view. Only about 26° directly in front is seen with both eyes. Chicks reach their peak sharpness of vision within 48 hours of hatching. The ear has no outer flap, and a single bone, the columella, replaces the three middle-ear bones of mammals.

A chicken's main hormone glands in the body cavity are two separate thyroid glands at the entrance to the chest and two small adrenal glands at the front end of the kidneys, next to the gonads. The thyroid hormones control metabolic rate, growth and moult; the adrenals make corticosterone, the main stress hormone of birds. The tiny parathyroid glands just behind the thyroids control blood calcium, which a laying hen needs for every eggshell.

• Thyroid glands: Make thyroid hormones (thyroxine, T4, and triiodothyronine, T3) that set the metabolic rate and control growth, moult and feather development.
• Adrenal glands: Make corticosterone (the main stress and metabolic hormone in birds), aldosterone, and adrenaline and noradrenaline.

Chickens have two primary lymphoid organs: the bursa of Fabricius, where B-cells mature, and the thymus, where T-cells are trained. Poultry Hub notes that B-cells move into the bursa from about day 15 of incubation until about 10 weeks of age, and that early damage from Gumboro or Marek's disease stops this programming for life. The bursa is present in birds under about a year old.

• Bursa of Fabricius: Trains B-cells, the white blood cells that make antibodies. B-cells were discovered through this organ.
• Thymus: Trains T-cells.
• Spleen: Filters blood and is a meeting place for B- and T-cells; chickens have no true lymph nodes.

A laying hen makes a new shell almost every day, and much of it forms at night, when she is not eating. She bridges the gap with medullary bone: a spongy, temporary bone that grows inside the marrow cavities of her long bones. Canoville and colleagues describe it as a sex-specific, estrogen-dependent tissue that, among living reptiles, birds and mammals, is found only in female birds. In laying pullets it has been seen in most of the skeleton, although only in small amounts in the skull, humerus and feet. (Canoville, Schweitzer & Zanno (2019): systemic distribution of medullary bone in the avian skeleton, BMC Evolutionary Biology.)

The numbers show why it matters. Poultry Hub notes that medullary bone starts forming about 10–14 days before the first egg, and that a shortage of calcium can lead to cage layer fatigue. The University of Kentucky's extension article puts the share of shell calcium that comes from bone at 47%, with the rest from the diet. When you read a chicken skeleton diagram, remember that the hollow-looking leg bones of a laying hen are, in life, partly filled with this calcium store. (Poultry Hub (Australia): skeletal system of the fowl.)

The wild type is the single comb, one upright blade of tissue. Two dominant mutations change it. Pea comb, caused by an amplified stretch of DNA inside the SOX5 gene, shrinks the comb and wattles into three low rows; Wright and colleagues linked this to cold climates, where a small comb loses less heat. (Wright et al. (2009): copy number variation in SOX5 causes the Pea-comb phenotype, PLoS Genetics.)

Rose comb is caused by a large chromosomal inversion that switches on the MNR2 gene where it should be silent, giving a flat, bumpy comb with a spike at the back. In homozygous males the same rearrangement also reduces sperm motility. A bird with both rose and pea alleles has a walnut comb, the classic example of epistasis that Bateson and Punnett described over a century ago. (Imsland et al. (2012): the Rose-comb mutation in chickens, PLoS Genetics.)

The two breast muscles sit in different compartments. The pectoralis lies on the surface; the supracoracoideus (the tenderloin) lies underneath it, pressed against the keel. In fast-growing meat chickens the deep muscle is tightly enclosed, and its blood supply can fail during vigorous wing flapping. The result is deep pectoral myopathy, seen at necropsy as a necrotic supracoracoideus under an apparently normal superficial breast muscle. (MSD Veterinary Manual: deep pectoral (supracoracoideus) myopathy in chickens (image).)

Researchers are still studying how the two muscles interact. A 2025 study of broilers examined injury and fibrosis where the pectoralis major and supracoracoideus join their tendinous sheets (the myoaponeurotic junction), and found coagulative necrosis in the supracoracoideus of one bird. For anatomy students, the takeaway is simple: the breast is two muscles with opposite jobs, one pulling the wing down and one lifting it, and both attach to the keel. (Kawasaki et al. (2025): pectoralis major and supracoracoideus myoaponeurotic junction in broilers, Journal of Poultry Science.)

Most chicken diagrams are drawn from the left side, because that is where the hen's single ovary and oviduct lie. Start with landmarks you can feel on a live bird: the crop at the base of the neck, the keel down the middle of the breast, the pubic bones on each side of the vent. Then place the organs between them. The heart sits just behind the crop, the liver lobes wrap around it, and the gizzard sits behind the liver. (Poultry Hub: digestive system of the fowl.)

Feathers make a chicken look much larger than its skeleton. In the 3D model, fade the feathers and notice how far the knee and the keel sit inside the outline. The visible bend at the bottom of the feathered leg is the hock (ankle), not the knee, and the thigh bone is hidden under the body plumage. Many worksheet mistakes come from labeling the hock as the knee. (Jacob, University of Kentucky / Extension Foundation: external anatomy of chickens.)

Use the 3D model or the diagrams above to answer these.

1. Which joint is the visible backward bend of a chicken's leg? (The hock, or ankle.)
2. Name the two parts of a chicken's stomach. (Proventriculus and gizzard.)
3. On which side is the hen's working ovary? (The left.)
4. Which muscle is the tenderloin? (The supracoracoideus.)
5. Where does an egg spend most of its 25–26 hours? (The shell gland, about 20 hours.)
6. Which bone is inside a wing drumette? (The humerus.)
7. What is the white cap on a chicken dropping? (Uric acid from the kidneys.)
8. How many air sacs does a chicken have? (Nine in most poultry references; some texts count eight.)