Veterinary Anatomy Flashcards

Question

The following are classified as tonsil with crypt, EXCEPT: a palatine tonsil of horse b tubal tonsil of pig c paraepiglottic tonsil of cat d lingual tonsil of pig

Answer 1

c ## Footnote Tonsillar crypts are invaginations or furrows that can be found on the surface of some tonsils. The primary function of tonsillar crypts is to increase the surface area of the tonsils, allowing for greater exposure of lymphoid tissue to the substances passing through. This facilitates the immune response by capturing and trapping antigens. The trapped substances are then presented to immune cells.

Answer 2

b ## Footnote It is constant in all domestic animals that the number of sternal ribs is one more than the number of sternebrae.

Answer 3

b ## Footnote Occipital myotomes are the origin of the tongue muscles that migrate rostrally into the swellings on the floor of the pharynx.

Answer 4

b ## Footnote The corona radiata is the innermost layer of the cells of the cumulus oophorus and is directly adjacent to the zona pellucida, the inner protective glycoprotein layer of the ovum. For fertilization to occur, sperm cells rely on hyaluronidase (an enzyme found in the acrosome of spermatozoa) to disperse the corona radiata.

Answer 5

b ## Footnote The left and right liver lobes of ruminants are undivided, unlike in carnivores and pigs. In horses, only the right liver lobe is undivided.

Answer 6

b ## Footnote The ovary of a mare has an exact location where the ovum is being ovulated. This is called the ovulation fossa and is unique in the ovary of mares.

Answer 7

a ## Footnote The sclera is the white part of the eye. Together with the transparent outer cornea, they form the fibrous tunic of the eye.

Answer 8

b ## Footnote Supracondylar foramen is a unique foramen in the distal end of the humerus of a cat. The structure is located at the medial side.

Answer 9

d ## Footnote Sartorius is a long muscle of the cranial part of the thigh. Aside from horse, cats have undivided sartorius muscle.

Answer 10

d ## Footnote Placentome is the term used for the combined caruncle (dam component) and cotyledon (fetal component) in the placenta. This is present in all female ruminants like cow, ewe and doe. This is absent in male animals like bull.

Answer 11

a ## Footnote In an adult ruminant, the rumen is the largest compartment of the forestomach. However, in a newly-born and young ruminants, the abomasum is the largest. The change in size correlates with the change in the diet from milk to grass.

Answer 12

a ## Footnote During early embryonic development, the gut tube is divided into three segments: the foregut, midgut, and hindgut. The foregut is located closest to the head and gives rise to several important organs, including the esophagus, stomach, liver, gallbladder, and pancreas. The pancreas arises as two buds from the foregut endoderm. The ventral pancreatic bud arises from the ventral wall of the foregut, while the dorsal pancreatic bud arises from the dorsal wall. These buds eventually fuse together to form the mature pancreas.

Answer 13

d ## Footnote In the thoracic limb, the cephalic vein is superficially located and easily accessible for drawing blood.

Answer 14

c ## Footnote Although variation exists depending on the reference and breed of the animal, dog’s heart are normally located between the 3rd and 7th rib.

Answer 15

d ## Footnote Brown Adipose Tissue (BAT) is composed by mitochondrial rich, multilocular adipocytes. This is abundant in rodents located at their interscapular region. Brown fat produces heat to help maintain body temperature in cold conditions.This tissue is important in hibernating animals like rodents.

Answer 16

c ## Footnote Omasal lymph node is a subdivision of the gastric lymph node in ruminants. Gastric lymph node is part of the coeliac lymphocenter.

Answer 17

a ## Footnote The udder of ruminants and horses are located in the inguinal region; thoracoabdominal in cats; thoracoabdominoinguinal in dogs and pigs.

Answer 18

a ## Footnote In dogs, thymus is situated at the cranial mediastinum.

Answer 19

b ## Footnote The spinal accessory, CN XI, carries sensory and motor information for the muscles of the head and upper neck. Brachiocephalicus is a muscle that extends from the arm to the head covering the neck region of the dog. Vagus (CN X) is the longest cranial nerve and provides sensory and motor control for the major internal organs, including the heart and the digestive tract Trochlear nerve (CN IV) is the smallest cranial nerve and carries motor neurons that control other muscles of the eye. Hypoglossal nerve (CN XII) is the last cranial nerve and acts as motor nerves to the tongue.

Answer 20

b ## Footnote Large ruminant kidneys are lobated like a bunch of grapes and lack renal pelvis. Formed urine directly move from minor to major renal calyces then to the ureter without the renal pelvis.

Answer 21

d ## Footnote Kidneys are described to be located in the retroperitoneal space. Organs are retroperitoneal if they have peritoneum on their anterior side only. The kidneys of most animal species are bean-shaped and located in the dorsal part of the abdominal cavity just ventral to the first few lumbar vertebrae. The right is always higher in most domestic animals except in pigs which are of the same level.

Answer 22

a ## Footnote Eggs can be classified based on the amount of yolk and based on its distribution. Based on the amount: Alecithal egg - the egg contains no yolk Microlecithal egg -the egg contains small or negligible amount of yolk Mesolecithal egg - the egg contains moderate amount of yolk Macrolecithal - the egg contains large amount of yolk Based on the distribution: Isolecithal - the very little amount of yolk present is uniformly distributed throughout Telolecithal - eggs containing moderate or large quantities of yolk and the distribution of yolk is not uniform. lt is concentrated more toward the vegetal pole.

Answer 23

b ## Footnote The capacity for exchange between maternal and fetal tissues is enhanced by the increased surface area. This is made possible by a folded, villous, or lamellar interface. In the folded placenta, the fetal–maternal contact surface is increased by the presence of vascularized macroscopic folds (plicae) of varying magnitude and microscopic ridges (rugae) of varying height (sow). In the villous placenta, the allantochorion forms cotyledons (i.e., arborizing chorionic villi with vascular mesenchymal cores that fit into corresponding caruncular crypts). Together, the villi and crypts form macroscopic (ruminants) or microscopic placentomes (mares), or independently, the villous tree extends into the maternal intervillous blood space (humans). In lamellar placentation, the trophoblast of the allantochorion forms an intercommunicating network that envelopes the endothelium of maternal blood vessels (carnivores), or it is in direct contact with maternal blood in trophoblast-lined vascular channels (rats, mice, rabbits).

Answer 24

b ## Footnote Nissl bodies are composed of rough endoplasmic reticulum (RER) at the cytoplasm of neurons and are responsible for the synthesis of proteins. They are named after the German neurologist and psychiatrist, Franz Nissl, who first described them.

Answer 25

b ## Footnote Triceps brachii, from the name itself, is a muscle with three heads. This is true in all domestic animals, except in dogs with the addition of the accessory head. The triceps brachii is considered as the strongest extensor of the elbow.

Answer 26

d ## Footnote Male ruminants and pigs have fibroelastic-type of penis. Erection is made possible by the straightening of the sigmoid flexure.

Answer 27

d ## Footnote Large ruminant tongue has a dorsal bulge called torus linguae.

Answer 28

b ## Footnote There are three lobes in the bird kidneys: cranial, middle and caudal lobes.

Answer 29

a ## Footnote The joints between the three sacral vertebrae are fused completely, forming a single sacrum with the segments joined by synostoses. Synostosis is the osseous union between cartilaginous or fibrous tissues in syndesmosis, symphysis, or synchondrosis.

Answer 30

a ## Footnote Mare has a distinct bean-shaped or kidney-shaped ovaries because of the presence of ovulation fossa.

Answer 31

a ## Footnote Four fetal membranes develop in a conceptus. Two arise from the trophoblast layer of the blastocyst (and are continuous with the somatopleure of the embryo). Two arise from the inner cell mass of the blastocyst (and are continuous with splanchnopleure of the embryo). 1. Chorion - forms the outer boundary of the entire conceptus (from trophoblast). 2. Amnion - encloses the embryo within a fluid-filled amnionic cavity; formed by folds of the chorion in domestic mammals. 3. Allantois - is highly vascular and provides the functional vessels of the placenta, via umbilical vessels. 4. Yolk sac - continuous with midgut splanchnopleure (develops early with hypoblast formation from inner cell mass). Supplied by vitelline vessels, it forms an early temporary placenta in the horse and dog. Yolk sac is most important in egg-laying vertebrates.

Answer 32

b ## Footnote The pulmonary and aortic valves can be located almost at the same level, but pulmonary valve is slightly more cranial in position.

Answer 33

a ## Footnote Thoracocentesis is an invasive procedure to remove air or liquid from pleural spaces for therapeutic or diagnostic purposes. The site for thoracocentesis can be identified through the use of landmarks. In the horse, it is the 7th - 8th intercostal space on left side and 6th and 7th intercostal space on the right side.

Answer 34

a ## Footnote In dogs, the left subclavian artery arises from the aortic arch together with the brachiocephalic trunk. This is also true in pigs. However, in large animals like cattle and horse, only the brachiocephalic trunk arises from the aortic arch and their left subclavian artery arises from the brachiocephalic trunk.

Answer 35

a ## Footnote Dog has a vascular or musculocavernous-type of penis. Ruminants and pig have fibroelastic-type of penis.

Answer 36

b ## Footnote Renal notch is a shallow concavity at the right hepatic lobe of all domestic animals except pig. Note that the right kidney is always higher than the left (except in pigs). This arrangement caused a concavity to accomodate the kidney which is just below the liver.

Answer 37

b ## Footnote The spleen of a chicken is round and is attached closed to the gizzard. It is boot-shaped in dog, falciform or hook-like in horse, tongue-like in pig, leaf-like in small ruminants and strap-like in large ruminants.

Answer 38

c ## Footnote The ribs of birds are different from mammals as it has a hook-shaped projection called uncinate process. This process is present at the vertebral ribs of the chicken and it projects caudally.

Answer 39

c ## Footnote The frog is the wedge-shaped structure between the sole, bars, and bulb of the equine hoof. It is often called the heart of the horse's foot because its compression forces blood out of the foot back toward the body. The frog is homologous with other species' digital pads.

Answer 40

a ## Footnote Lymph nodes can be palpable and can be used in assessing the condition of the animals especially in dogs. Among the choices, the medial retropharyngeal lymph node is the deepest and lies between the larynx and wing of the atlas. It is not normally palpable. The rest of the choices are normally palpable.

Answer 41

b ## Footnote Birds lack colon. The ileum is connected directly to the rectum at the ileocecal junction.

Answer 42

c ## Footnote The heart is composed of three layers, which are, from the outermost to the innermost: Epicardium: This is the outermost layer of the heart, also known as the visceral pericardium. It is a thin, smooth layer of connective tissue that covers the surface of the heart and forms part of the pericardium. Myocardium: This is the middle and thickest layer of the heart, and it is composed of specialized cardiac muscle tissue. The myocardium is responsible for the contraction and relaxation of the heart, which generates the force needed to pump blood throughout the body. Endocardium: This is the innermost layer of the heart, which lines the interior of the heart chambers and covers the heart valves. It is composed of a thin layer of endothelial cells that help to prevent blood clots and regulate blood flow through the heart.

Answer 43

b ## Footnote During embryonic development, the liver initially forms as a simple, hollow tube, known as the hepatic diverticulum or liver bud, which arises from the endoderm of the foregut. The hepatic diverticulum then grows and divides to form the complex structure of the liver. As the liver bud grows, it gives rise to several outgrowths, including a small outpouching known as the cystic diverticulum or cystic bud. The cystic bud eventually gives rise to the gallbladder and cystic duct, which play important roles in the storage and transport of bile. Rats (and some other rodents) do not have a gallbladder.

Answer 44

a ## Footnote The spermatic cord is a bundle of connective tissue, blood vessels, nerves, and ducts that extend from the abdomen to the testicles. It includes the testicular artery, veins, lymph, and the deferent duct. The seminiferous tubule forms the parenchyma of the testes and is where the spermatozoa are produced.

Answer 45

d ## Footnote Supratrochlear foramen is a direct opening between the radial and olecranon fossae of the dog's humerus. This is present only in dogs and interestingly, no structures pass through it.

Answer 46

b ## Footnote The cloaca of a bird is composed of three segments, the coprodeum, urodeum and proctodeum, serving different functions. Anatomically, the coprodeum is the first segment right after the rectum.

Answer 47

c ## Footnote The upper dental arcade of small and large ruminants lacks incisors. In replacement, they have a dental pad which is described as a thick, hard gum line.

Answer 48

c ## Footnote Mc III or the cannon bone is the only functional and weight-bearing metacarpal bone of horses. Mc II and Mc IV are attached to the Mc III and are called splint bones. Mc I and Mc V are missing.

Answer 49

c ## Footnote A zygote is the first diploid cell that is formed by the fusion of male and female gametes resulting in the formation of an embryo. The zygote stage development occurs in the first week of fertilization. The correct sequence of embryonic development is: Zygote - Morula - Blastula - Gastrula - Embryo.

Answer 50

c ## Footnote A hemipenis (plural hemipenes) is one of a pair of intromittent organs of male squamates (snakes, lizards and worm lizards). They are usually held inverted within the body, and are everted during reproduction.

Answer 51

a ## Footnote The primitive urogenital sinus gives rise to urinary bladder, urethra and vestibule in the female embryo. In the male embryo, it gives rise to the bladder and penile urethra. The cervix arises from paramesonephric duct.

Answer 52

b ## Footnote The coeliac artery is one of the unpaired branches of the abdominal aorta. Only the left gastric artery, splenic artery and hepatic artery arises from it. The right gastric artery arises from the hepatic artery.

Answer 53

d ## Footnote All statements are anatomically correct.

Answer 54

a ## Footnote The nodes of Ranvier, also known as myelin sheath gaps, are regularly spaced gaps in the myelin sheath that surrounds axons of neurons in the nervous system. The myelin sheath is a fatty insulating layer that increases the speed of nerve impulses along the axon. The nodes of Ranvier are important for the efficient propagation of action potentials, which are the electrical signals that neurons use to communicate with each other. These gaps allow the action potential to "jump" from one node to the next, a process known as saltatory conduction. This allows the signal to travel quickly down the axon, while conserving energy and resources for the neuron.

Answer 55

d ## Footnote Sudan IV (Red) is a fat-soluble dye that stains lipids red. Two layer indicates the presence of water-insoluble substances like fats, with red color on the top layer.

Answer 56

c ## Footnote The horse has a total number of 18 rib pairs. Take note that the number of rib pairs is equal to the total number of thoracic vertebrae. Ruminants have 13, the pig has 14 and dog has 13 rib pairs.

Answer 57

c ## Footnote Onychectomy (declaw removal) is an elective surgery that requires removal of the third phalanx that renders cats unable to scratch.

Answer 58

b ## Footnote The primitive gut, also known as the embryonic gut tube, is the precursor to the digestive system and associated organs in developing embryos. The gut tube initially consists of a single layer of cells, but it soon undergoes a process of elongation and folding that divides it into three main segments: the foregut, midgut, and hindgut.

Answer 59

c ## Footnote Chicken lacks male accessory sex gland. The ejaculate is composed of sperm and scant additional secretions produced by the testes and the walls of the ducts.

Answer 60

d ## Footnote In case of Marek's disease, there will be a unilateral enlargement of the sciatic nerve. This is suggestive of the neural form of the disease.

Answer 61

d ## Footnote During embryonic development, the fourth aortic arch gives rise to the proximal portion of the right subclavian artery. The subclavian arteries are major arteries that supply blood to the arms, chest, and back. They arise from the brachiocephalic trunk (in the case of the right subclavian artery) or directly from the aortic arch (in the case of the left subclavian artery).

Answer 62

b ## Footnote Placentation can be classified based on placental shape and contact (diffuse, cotyledonary, zonary or discoid) or based on the layers between fetal and maternal blood (epitheliochorial, endotheliochorial, hemichorial or syndesmochorial). Dogs and cats have endotheliochorial, zonary type of placentation.

Answer 63

a ## Footnote Prostate gland is located around the pelvic urethra forming a ring-like structure as it encloses the structure. Enlargement as in the case of cancer impedes the flow of urine as in the case of dogs.

Answer 64

b ## Footnote The cranial drawer test is performed in dogs to detect rupture of the cranial cruciate ligament that results in cranial displacement of the tibia relative to femur. The caudal cruciate ligament has antagonistic action to the CrCL, and is rarely affected.

Answer 65

b ## Footnote Thymus gradually involute until the animal reaches sexual maturity. Regression starts at the cranial, cervical part of the organ, so that the thoracic part remains longer. As it decreases in size and loses its lymphoid structure, it is replaced by fat.

Answer 66

a ## Footnote The hyoid apparatus is located at the intermandibular space which stabilizes the tongue and the larynx by suspending them from the skull. The chronological order of hyoid bone is Stylohyoid, Epihyoid, Ceratohyoid, Basihyoid, and Thyrohyoid. (Remember: Sick Elephants Can Be Treated)

Answer 67

b ## Footnote The term "interzone" refers to the region between two developing skeletal elements in the embryo, where joint formation occurs. Specifically, the interzone is the area where mesenchymal cells condense and differentiate into chondrocytes, which form the cartilage template of the joint. The interzone is important in the development of synovial joints, which are the most common type of joint in the body.

Answer 68

b ## Footnote Among the pads of dogs, the metacarpal pad (or even the metatarsal pad) is characteristically heart-heart shaped as shown in paw prints. Note that dogs lack tarsal pads.

Answer 69

d ## Footnote Among domestic animals, the follicles in the ovary of sow are very evident and look like a bunch of small grapes.

Answer 70

c ## Footnote Bursa of Fabricius is the dorsal outpouching of the proctodeum or most distal portion of the cloaca.

Answer 71

b ## Footnote Horse stomach is relatively small in relation to its size. It is divided into a glandular and non-glandular part by a distinct structure called margo plicatus. Note that horse is an example of hindgut fermenter in which the cecum plays a very important role in the digestion of feedstuff.

Answer 72

a ## Footnote The hamstring group of muscles includes the biceps femoris (lateral), semitendinosus (middle) and semimembranosus (medial). These are the superficial muscles of the hip and thigh and attach proximal and distal to the stifle joint.

Answer 73

b ## Footnote Supraspinatus is an intrinsic muscle of the thoracic limb. It originates from the supraspinous fossa of the scapula and inserted at the greater tubercle of the humerus. Take note that both supraspinatus and infraspinatus are inserted at the greater tubercle. They only differ in the origin.

Answer 74

a ## Footnote The hoof wall is composed of three distinct layers of stratum corneum. Stratum externum, or periople, is the thin, outermost layer of the hoof wall. Stratum medium, or tubular horn, is the middle and thickest layer of the hoof wall. This layer also may contain pigment. Stratum internum is the innermost layer of the hoof wall. This layer is produced by the epithelium of the laminar epidermis and is fused to the stratum medium, forming a relatively contiguous hoof wall.

Answer 75

d ## Footnote All the statements correctly described the position of the ovaries of bitch.

Answer 76

d. prosencephalon ## Footnote The three primary brain vesicles include the prosencephalon (cranial), mesencephalon (middle) and rhombencephalon (caudal). The prosencephalon will further subdivide into telencephalon (future cerebrum) and diencephalon (future thalamus and hypothalamus).

Answer 77

c. proventriculus ## Footnote Petechial hemorrhages in the proventriculus can be a pathognomonic lesion in Newcastle disease.

Answer 78

b. vein ## Footnote Arteries have thick walls. Veins have thin walls but typically have wider lumen. Their walls are considerably less elastic, less muscular, and their lumens are correspondingly larger in diameter, allowing more blood to flow with less vessel resistance. However, lumen size may vary depending on the specific artery or vein.

Answer 79

b. pituitary gland ## Footnote The term "sella turcica" is derived from Latin and means "Turkish saddle" due to its distinctive shape. It is named so because it resembles a saddle used in horseback riding, with its anterior and posterior clinoid processes resembling stirrups. It is a bony structure located at the base of the skull, in the sphenoid bone. It houses the pituitary gland.

Answer 80

b. liver ## Footnote During fetal development, the organ that occupies most of the space in the abdominal cavity is the liver. As the liver grows and develops, it pushes the developing midgut out of the abdominal cavity and into the umbilical cord, a process known as physiological herniation. The umbilical herniation of the midgut is a temporary and normal process that allows for the proper development of the gastrointestinal tract in the fetus.

Answer 81

c. presence of angular process in the mandible of dog ## Footnote Angular process is present at the angle of the mandible of carnivores like dogs thus goats lack this structure. Both coronoid and condyloid processes are present in both animals. Coronoid process is higher than the condyloid process in all species except in pig. The same height of condyloid and coronoid processes is a feature of a pig’s mandible.

Answer 82

c. T13 ## Footnote The anticlinal vertebra of ruminants is the last thoracic vertebra. Anticlinal vertebra is defined as the thoracic vertebra with the most vertically oriented spinous process and is important as landmark especially in radiology.

Answer 83

a. it will degenerate ## Footnote The second aortic arch regresses early, but a remnant forms portions of the hyoid and stapedial arteries.

Answer 84

b. radial nerve ## Footnote The triceps brachii is the strongest extensor of the thoracic limb. From its name, it has three heads (long, lateral, and medial heads) with the addition of accessory head in dogs. All heads of the triceps brachii are innervated by the branches of the radial nerve.

Answer 85

b. shape like a hook ## Footnote The spleen of a horse is falciform or hook-liked in appearance. Dog has a boot-shaped, chicken has a marble-shaped, pig has a tongue-shape and goat and sheep have a leaf-shaped spleen.

Answer 86

a gizzard ## Footnote The ventriculus or gizzard serves as the muscular or mechanical stomach of the birds. Normally, there are grits inside the organ to assist in the physical grinding of feeds.

Answer 87

a ## Footnote The greater omentum is the first structure seen after removing the abdominal muscle.

Answer 88

a ## Footnote The vestibular apparatus is part of the inner ear and is responsible for sensing head movements and changes in position. It consists of the semicircular canals, the utricle, and the saccule. The inner ear, including the vestibular apparatus, arises from the otic placode, which is a thickened patch of ectodermal cells that forms on the surface of the developing embryo. During embryonic development, the otic placode invaginates to form the otic vesicle, which eventually gives rise to the cochlea and the vestibular apparatus.

Answer 89

b ## Footnote Lymph heart is an elongated, dorsoventrally flattened organ of birds located outside the body cavity. It is situated at the caudal end of the synsacrum, dorsal to the transverse process of the first free caudal vertebra. In species with a well-developed copulatory apparatus and a protrusible phallus, such as ratites and water birds, the lymph heart is usually integrated into the specialized lymphatic system of the copulatory organ

Answer 90

a ## Footnote The number of premolar teeth of horses varies from 3 to 4 with a total number of 40 – 42 teeth. 1st Premolar is usually absent and when present, it is almost always seen only in the upper arcade and is termed wolf tooth, which is smaller and does not come into wear.

Answer 91

c ## Footnote A plane is a surface, real or imaginary, along which any two points can be connected by a straight line. Median plane – divides the head, body, or limb longitudinally into equal right and left halves Sagittal plane - passes through the head, body, or limb parallel to the median plane. Transverse plane - cuts across the head, body, or limb at a right angle to its long axis, or across the long axis of an organ or a part. Dorsal plane or Frontal plane- runs at right angles to the median and transverse planes and divides the body or head into dorsal and ventral portions.

Answer 92

c ## Footnote The pulmonary trunk arises from the primitive pulmonary artery, which is a structure that develops from the embryonic truncus arteriosus. During early embryonic development, the heart tube undergoes a series of complex morphological changes that eventually give rise to the mature heart. One of the key structures that forms during this process is the truncus arteriosus, which is a single outflow tract that connects the developing heart to the aortic sac.

Answer 93

c ## Footnote The retina is the only member of the inner or nervous tunic of the eyeball.

Answer 94

a ## Footnote Medial retropharyngeal lymph node lies between the larynx and wing of the atlas. Although considered as the largest lymph node of the head and neck, it is not normally palpable. It is present in all domestic animals.

Answer 95

d ## Footnote The coronary sinus is located ventral to the caudal vena cava. It receives the venous return for most of the blood from the heart itself.

Answer 96

d ## Footnote Interdigital pouches are found above the hoof of all limbs of the sheep. It is not found in horses. The rest of the pairing in the choices are correct.

Answer 97

a ## Footnote Unlike other domestic animals, the Supraorbital foramen is uniquely missing in dogs. The rest among the choices are present.

Answer 98

b ## Footnote The distal end of the deferent duct or vas deferens is enlarged and has secretions. This is called the ampullary gland.

Answer 99

a ## Footnote Hinge joint - extension and flexion. Ball-and-socket joint - abduction/adduction, flexion/extension, circumduction.

Answer 100

c ## Footnote 3:3 - Epitheliochorial 2:3 - Syndesmochorial 1:3 - Endotheliochorial 0:3 - Hemochorial

Answer 101

b ## Footnote The nucleus pulposus is derived from notochord while other connective tissues of the spine are derived from sclerotome.

Answer 102

a ## Footnote Among the choices, anatomically, dog and goat, have almost the same kidney.

Answer 103

a ## Footnote Horse has a false nostril or also known as the nasal diverticulum. This is a dorsal passage through the horse’s nostril into a blind cutaneous pouch.

Answer 104

a ## Footnote Unlike other domestic animals, the apex of the heart of a dog is characteristically blunt.

Answer 105

c ## Footnote Placentation can be classified based on placental shape and contact (diffuse, cotyledonary, zonary or discoid) or based on the layers between fetal and maternal blood (epitheliochorial, endotheliochorial, hemichorial or syndesmochorial). Rodents like mouse have hemochorial, discoid type of placentation.

Answer 106

a ## Footnote The atlanoaxial joint is a joint between the atlas and the axis. The dens (odontoid process) of the axis rotates with the vertebral foramen of the atlas. Ginglymus (hinge) - joints move only in their sagittal plane. The movements in this type of joint are flexion, extension, and, in some joints, hyperextension. (Ex: fetlock) Plane joints - have only a slight gliding movement between relatively flat apposed surfaces. These surfaces are called facets. (Ex: joints between adjacent carpal bones) Trochoid (pivot) joint - one in which rotary movement occurs around one axis (atlantoaxial joint) Spheroid (ball and socket) joints – permit movement in nearly any direction. A spherical head on one bone fits into a cup-shaped depression in the other. Flexion, extension, adduction, abduction, rotation, and circumduction are all possible in spheroid joints. (Ex: coxofemoral joint)

Answer 107

c ## Footnote Birds are unique from mammals because they have renal portal system. The renal portal system is a second route by which blood moves from the caudal half of the body through the kidneys before returning to the heart. The system has been used as a justification for avoiding the caudal body as a site for injection of medications in birds.

Answer 108

b ## Footnote The liver of pig is the same with other animals except that the papillary process of the caudate lobe is missing.

Answer 109

a ## Footnote Only the left side of the female reproductive tract of hen is normally developed. The right side regresses during embryonic development.

Answer 110

a ## Footnote The muscles of the tongue include the styloglossus, hyoglossus, genioglossus, and lingual intrinsic muscles. Styloglossus – extends from the stylohyoid to the tongue. It has three muscle heads that inserts at the tongue at different level. It draws the tongue caudally. Genioglossus- thin, triangular muscle at the intermandibular space ventral to the tongue. Contraction draws the entire tongue rostrally. It depresses the tongue. Hyoglossus – located at the root of the tongue. It retracts and depresses the tongue.

Answer 111

c ## Footnote Structures found surrounding the oocyte, from innermost to outermost, are: vitelline membrane, zona pellucida, and corona radiata. Since the corona radiata is the outermost among the choices, the sperm makes first contact with it during fertilization.

Answer 112

b ## Footnote In general, the radius is more massive than the ulna. However, this is not true in birds as the ulna is more massive than the radius.

Answer 113

b ## Footnote The angular process is a projection found at the angle of the mandible of carnivores and other small mammals like rodents and rabbits. It is absent in other animals.

Answer 114

a ## Footnote In horse, ergot is a small mass of horny material on the palmar/plantar surface of the fetlock. They are buried in the feathers (long hair behind the fetlock). Chestnut or night eyes are horn-like growths on the medial sides of horses’ limbs. The front chestnuts are proximal to the carpus, and the hind chestnuts are slightly distal to the hocks. The chestnuts are thought to be vestigial metacarpal and metatarsal footpads. Contour feathers are the covering feathers giving shape and color to the birds. Digital pads are keratinized cushion-like surface on the digits in carnivores.

Answer 115

b ## Footnote Blood collection is essential in the surveillance of any disease investigation. Among the choices, jugular vein is the best option in pigs. Other possible sites include the ear vein, cranial vena cava, and the heart (non-survival).

Answer 116

c ## Footnote Ruminants have a total of 5 tarsal bones. Centroquartal bone is the fused central tarsal bone and 4th tarsal bone. The rest are found in the tarsus of other domestic animals.

Answer 117

a ## Footnote Elastic tissue is characterized by numerous regularly or irregularly arranged elastic fibers. It is exemplified by the ligamentum nuchae of grazing animals and by the vocal ligaments.

Answer 118

d ## Footnote The heart originated from the splanchnic mesoderm, which is a layer of mesodermal tissue that surrounds the developing gut. As the embryo develops, a pair of regions within the splanchnic mesoderm begin to fold and fuse together to form the primitive heart tube. This tube eventually gives rise to the four chambers of the adult heart, as well as the major blood vessels that supply blood to the body.

Answer 119

a ## Footnote The common carotid arteries can arise separately or via bicarotid trunk. They arise separately in dogs and cats. In hooved animals (ruminants, pig and horse) arise from a short common bicarotid trunk.

Answer 120

a ## Footnote The horse has the least number of lung lobes because it lacks the cardiac or the middle lobe.

Answer 121

a ## Footnote Carnivores, like dogs and cats, have only simple glandular stomach.

Answer 122

a ## Footnote Tusks are elongated, continuously growing front teeth that protrude well beyond the mouth of certain mammal species. They are most commonly canine teeth, as with pigs and walruses, or, in the case of elephants, elongated incisors.

Answer 123

b ## Footnote From the name itself, gluetobiceps is a fused muscle between the biceps femoris and superficial gluteal muscle. This muscle is present in ruminants and in pig. In other animals, these are classified as individual muscles.

Answer 124

b ## Footnote Between the right atrium and the right ventricle is the tricuspid valve. Between the left atrium and left ventricle is the bicuspid or the mitral valve. Remember, TRI before you BI.

Answer 125

c ## Footnote Among the choices, only the dog has a trachealis muscle located outside the trachea. The trachealis muscle is a muscle dorsal to the trachea “completing” the tracheal rings.

Answer 126

b ## Footnote The gallbladder arises from the hepatic diverticulum, which is an outpouching of the endodermal layer of cells that lines the developing liver bud.

Answer 127

d ## Footnote Hemal nodes, also known as hemolymph nodes or splenolymph nodes, are lymphoid organs found in various mammals (especially prominent in ruminants) and some birds. Hemal nodes appear similar to lymph nodes in the structure of their lymphoid follicles and to the spleen in the structure of its lymphoid cords. It is presumed to have the same function as the spleen.

Answer 128

a | kala ko 3 haha you got me there ## Footnote The sacral vertebrae in horses and carnivores have spinous processes that are unfused while the sacral spinal processes in ruminants fuse into a median sacral crest.

Answer 129

b ## Footnote It is located at the lateral angle of the wing of the ilium. Tuber sacrale is located medially. Tuber ischiadicum (also known as an ischiatic tuber) are large roughened caudal prominence of the ischium and is known as the pin bone.

Answer 130

d ## Footnote The intercapital ligament joins the heads of each paired ribs, forming a reinforcing band across the dorsal intervertebral disk. This prevents excessive cranial and caudal movements of the ribs, and it is absent in the first pair and the last two pairs of ribs.

Answer 131

c ## Footnote The region of the sarcomere that has both thick and thin filaments is known as the A band. The A band is located in the center of the sarcomere and appears as a dark band under the microscope due to the presence of overlapping thick (myosin) and thin (actin) filaments.

Answer 132

a ## Footnote Skin is the largest organ in the body. It serves as a protective barrier between the internal organs and the external environment. It has several important functions, including regulating body temperature, protecting against pathogens, preventing dehydration, and sensing touch, pressure, and pain. The skin consists of three layers: the epidermis, dermis, and subcutis (also known as the hypodermis or subcutaneous tissue). Next to the skin is the liver, which is the largest internal organ.

Answer 133

c ## Footnote Bird nephron has both mammalian (with Loop of Henle) and reptilian-type (without Loop of Henle). The collecting duct is always present in both type of nephron. Their kidneys are closely attached to the synsacrum. They also lack urinary bladder as formed urine is directly excreted together with their feces.

Answer 134

a ## Footnote The tracheal bronchus specifically ventilates the cranial lobe of the right lung of pig and cattle.

Answer 135

c ## Footnote During the fetal period of lung formation, the phase that involves the gland-like ramification of the bronchial tree from lobar bronchi to terminal bronchioles is called the pseudoglandular phase. During this phase, he bronchial tree undergoes extensive branching, resulting in the formation of small airways that resemble glandular structures. The conducting airways develop and differentiate, with the branching of bronchi into bronchioles, and finally into terminal bronchioles.

Answer 136

c ## Footnote The common calcanean tendon or the Tendon of Achilles is a tendon formed by the gastrocnemius and the superficial digital tendon. It is inserted on the calcaneus. Separation of the tuber will result in a decreased function of the grastrocnemius to extend the stifle. Flexion of the digit will be little affected as the digital flexor tendons would still be functional.

Answer 137

d ## Footnote The clavicle is a separate, non-articulating bone present connecting the shoulder and sternum of cats. It should not be mistaken for a bone in the esophagus of a cat on lateral radiography. It is a rudimentary structure embedded in the brachiocephalicus muscle of a dog while it is absent in horses, pigs, and ruminants.

Answer 138

b ## Footnote The stomach of a horse is relatively small compared to its size. It is divided into a glandular and non-glandular zone by a distinct line called margo plicatus.

Answer 139

b ## Footnote Crown: This is the top part of the tooth. The shape of the crown enables different functions. For example, the incisors are sharp and are for cutting into food, while the molars have a flat surface for grinding. Gumline: This is where the gum and tooth meet. Root: The root acts as an anchor that keeps teeth in place. It is embedded in the jawbone and enables teeth to withstand the force of biting and chewing. Enamel: The enamel is the outer layer of the tooth. It is the hardest and most mineralized tissue in the body. Dentin: This is the layer underneath the tooth enamel surface. Dentin makes up the majority of a tooth's structure. Pulp: Is found in the center of the tooth; the pulp is a soft tissue that consists of nerve tissue and blood vessels.

Answer 140

a ## Footnote Nissl bodies occur in the body and dendrites of neurons, though not in the axon or axon hillock. They are consist of rough endoplasmic reticulum and are the main site of protein synthesis of neurons.

Answer 141

a ## Footnote In chicken, cervical and clavicular air sacs are unpaired. The rest are paired.

Answer 142

b ## Footnote The left subclavian artery of horse arises from the brachiocephalic trunk. Only the brachiocephalic trunk arises from the aortic arch of horse.

Answer 143

c ## Footnote The rachis is the rigid shaft of the feather.

Answer 144

a ## Footnote Cornual process is a process in the frontal bones of horned ruminants. This is absent in polled ruminants.

Answer 145

b ## Footnote Cattle and pig lacks renal crest because they have individual renal papillae. Their kidneys are lobated. The lobation is obvious in cattle and other large ruminants. The kidneys of pigs are lobated internally but has a smooth surface externally. Fused lobes mean fused renal papillae. Renal crest is a result of fused renal papillae.

Answer 146

d ## Footnote The Preen gland is also known as the uropygial gland or oil gland. This gland is used by the bird to waterproof their feather

Answer 147

c ## Footnote Patent ductus arteriosus, with reverse flow, allows unoxygenated pulmonary arterial blood to enter the systemic circulation caudal to the aortic vessels that supply the forelimbs, head and neck. This results on unoxygenated blood circulating initially to the more caudal trunk and pelvic limbs. The usual patent ductus arteriosus carries blood from higher pressure systemic circulation (aorta) to lower pressure pulmonic circulation. This is reversed under condition of pulmonary hypertension.

Answer 148

d ## Footnote Dogs, horses and pigs have a foramen lacerum at the junction of the temporal, sphenoid, and occipital bones. Among the three species, only dogs have a discrete foramen ovale and foramen lacerum while the foramen ovale in horses and pigs forms part of the large foramen lacerum.

Answer 149

b ## Footnote Tetralogy of Fallot is a birth defect that affects normal blood flow through the heart. It is a combination of four congenital heart defects. It includes the ventricular septal defect (VSD), pulmonary stenosis, a misplaced aorta, and a thickened right ventricular wall (right ventricular hypertrophy).

Answer 150

b ## Footnote The ribs of chicken are different from mammals as it has a vertebral rib and sternal ribs attached with one another. Notarium is the fused last cervical vertebra and the first three thoracic vertebrae. The rest of the statements are anatomically correct.

Answer 151

d ## Footnote Purring involves the rapid movement of the muscles of the larynx (voice box), combined with movement of the diaphragm (the muscle at the base of the chest cavity). The muscles move at around 20 to 30 times per second. As the cat breathes, air touches the vibrating muscles, producing a purr.

Answer 152

b ## Footnote The triceps brachii mm is the strongest extensor of the elbow joint. Damage to the muscle and its joint will make it difficult to extend the elbow.

Answer 153

c ## Footnote Supratrochlear foramen is present only in dogs. This is a foramen at the distal end of the humerus with no known structures passing through it. Greater tubercle is present in both humerus of dog. Olecranon process is present in the ulna of both species and not in the humerus. Intermediate tubercle is absent in both animals as this structure is present only in the horse.

Answer 154

a ## Footnote In zonary placentation, the placenta takes the form of a complete or incomplete band of tissue surrounding the fetus. This is seen in carnivores like dogs and cats, seals, bears, and elephants.

Answer 155

d ## Footnote Capillaries are characterized by their thin walls, which are composed of a single layer of endothelial cells. Capillaries can also be distinguished from other blood vessels by their lack of smooth muscle and elastic tissue in their walls.

Answer 156

b ## Footnote Among the vertebral column, the thoracic vertebrae have direct articulation with the ribs. The head of the ribs articulates with the costal fovea of the thoracic vertebra while the tubercle of the rib articulates with the transverse fovea of the thoracic limb.

Answer 157

b ## Footnote In carnivores, ruminant and horse, the cecum lies on the right half of the abdomen, except for the pig on which it is located on the left.

Answer 158

c ## Footnote Philtrum is a deep median groove between the upper lip and nasal plane of dog, cat and small ruminants. This is absent in pig, large ruminant and horse.

Answer 159

a ## Footnote Dogs and pigs have an incomplete orbit. In live animals, this is completed by the orbital ligament. This is often ossified in cats.

Answer 160

c ## Footnote Mt III is the only weight-bearing digit of the horse and is also known as the cannon bone.

Answer 161

a ## Footnote The triceps brachii is considered as the strongest extensor of the elbow. The brachialis muscle is the primary flexor of the elbow. The rest are also classified as flexors.

Answer 162

c ## Footnote Cornual process is a bony projection at the frontal bones of horned ruminants. In large ruminants, this is projected and oriented laterally. This is in contrast with the small ruminants in which the cornual process is situated at the dorsal side of the frontal bone.

Answer 163

b ## Footnote The buccinator maintains the tightness of the cheeks and presses them against the teeth during chewing. It also assists the tongue to keep the bolus of food central in the oral cavity. Digastricus (biventer), temporalis, and masseter are muscles of mastication. The digastricus opens the jaw while both temporalis and masseter close the jaw.

Answer 164

d ## Footnote Capsular veins are distinct veins present at the renal capsule surface of cat kidneys. These are tributaries of the renal veins.

Answer 165

b ## Footnote Tomcats have prostate gland. In addition, they have bulbourethral glands as accessory sex gland. The rest of the statements are correct.

Answer 166

d ## Footnote Cell division starts in a zygote following fertilization. A zygote is the first diploid cell that is formed by the fusion of male and female gametes resulting in the formation of an embryo. A series of cleavage from a zygote forms the morula. This means the zygote comes first before the morula, which is the mulberry-like structure.

Answer 167

b ## Footnote The parotid gland in cattle is located right behind the ear, and more superficial than the mandibular gland.

Answer 168

c ## Footnote The left ventricle has the thickest myocardial wall compared to all heart chamber. It actually forms the apex of the heart. This thickness is associated with its function of pumping blood to the systemic circulation.

Answer 169

b ## Footnote The splanchnic mesoderm forms the heart as well as the visceral layer of the serous pericardium and blood vessels. It also contributes to the smooth muscle and connective tissues of the respiratory and digestive organs.

Answer 170

a ## Footnote On the surface of every egg yolk there can be seen a tiny, whitish spot called the blastodisc. This contains a single female cell. If sperm is present when a yolk enters the infundibulum, a single sperm penetrates the blastodisc, fertilizing it and the blastodisc becomes a blastoderm. Cleavage occurs in the blastoderm of a fertilized egg, and in the blastodisc of an unfertilized egg.

Answer 171

c ## Footnote Horse kidneys are unique among domestic animals because the left is typically bean-shaped and the right is distinctly valentine heart-shaped. The function is the same for both kidneys.

Answer 172

a ## Footnote Among the choices, cattle has the most prominent torus lingua. It is not prominent in horse and sheep and is absent in carnvores like dog. The area is characteristically studded with conical papillae.

Answer 173

a ## Footnote The foramen ovale is a small opening in the septum, or wall, between the right and left atria of the fetal heart. During fetal development, this opening allows oxygenated blood to bypass the lungs and flow directly from the placenta to the developing brain and other organs. At birth, when the newly born animal takes its first breaths, the pulmonary circulation is established and the lungs begin to function properly. The increased oxygenation of blood flowing to the left atrium causes a decrease in pressure in the right atrium. This drop in pressure leads to a flap-like valve, called the septum primum, to cover the foramen ovale, thus closing the opening between the two atria.

Answer 174

c ## Footnote In the ocular form of Marek's disease, the color of the iris changes from the normal orange/red/yellow to gray.

Answer 175

c ## Footnote Development of the heart begins with the formation of two endothelial strands called the angioblastic cords. These cords canalize forming two heart tubes, which fuse into a single heart tube by the end of the third week due to lateral embryonic folding.

Answer 176

d ## Footnote Placentation can be classified based on placental shape and contact (diffuse, cotyledonary, zonary or discoid) or based on the layers between fetal and maternal blood (epitheliochorial, endotheliochorial, hemichorial). Ruminants have epitheliochorial, cotyledonary type of placentation.

Answer 177

b ## Footnote The nasal cartilage dictates the shape of the nostrils.

Answer 178

b ## Footnote The furcula or wishbone is a forked bone (y-shaped) found in most birds and is formed by the fusion of the two clavicles. Tarsometatarsus is rod-like and is formed by the fused distal row of the tarsal bone and metatarsal bone. The coracoid is one of four bones in the bird pectoral girdle. It is a short, thick bone connecting the sternum to the shoulder. Sclerotic rings are bony structures found surrounding the eyeball of birds. Since vision is so important to birds from finding food to watching for predators, or being able to judge distance for a smooth landing, having this bony ring keeps their vision as sharp as possible.

Answer 179

b ## Footnote Foramen ovale is an opening between the two atria during embryonic development. It is located in the developing interatrial septum and tends to close as the fetus develops to avoid the mixing of oxygenated and unoxygenated blood.

Answer 180

a ## Footnote Lyssa (or lytta in older references) lies on the ventral median plane in the free end of the tongue of a dog. It is a rodlike, flexible body that is supplied by the hypoglossal nerve, and is thought to act as a stretch receptor.

Answer 181

b ## Footnote The brachiocephalicus muscle is a broad muscle extending from the arm to the head. It is divided into cleidobrachials (arm part) and cleidocephalicus (head part) with the clavicular tendon (intersection) serving as the boundary. Remember that clavicle is absent in most domestic quadrupeds (except in cats).

Answer 182

c ## Footnote The cervix of sow has interdigitating structures called pulvini cervicales. This structure served as a lock in the cervix.

Answer 183

a ## Footnote The nervous system develops when the notochord induces its overlying ectoderm to become neuroectoderm and eventually to develop into the neural plate. The neural plate folds along its central axis to form a neural groove lined on each side by a neural fold. The two neural folds fuse together and pinch off to become the neural tube

Answer 184

d ## Footnote Birds, like mammals, have a 4-chambered heart.

Answer 185

b ## Footnote In general, depending on the species, there are a total of 9 air sacs present in birds. This is composed of paired (cervical, cranial thoracic, caudal thoracic and abdominal) and unpaired (clavicular) air sacs. However, in some references, birds have 8 airsacs with unpaired cervical.

Answer 186

b ## Footnote Lymphatic vessels, the loop of and the air sacs of avians are lined by simple squamous epithelium. Duodenum, being part of the gastrointestinal tract, is lined by simple columnar epithelium.

Answer 187

b ## Footnote Os cordis is an example of splanchnic bone present in large ruminants like cattle. (Although os cordis is reported in old horses). This bone is located at the junction between the atria and ventricles of the heart. Specifically, they are like rings that encircle the four heart orifices.

Answer 188

b ## Footnote The arrector pili is a muscle associated with hair follicles. It is a small, smooth muscle that is connected to each hair follicle in the skin. When the arrector pili muscle contracts, it causes the hair to stand on end, leading to what is commonly known as "goosebumps" or "piloerection." This phenomenon can occur in response to cold temperatures, fear, or emotional arousal. The arrector pili muscle contraction is a vestigial reflex inherited from our evolutionary ancestors, which helped to provide insulation or make animals appear larger when threatened.

Answer 189

b ## Footnote The teat or commonly referred to as the nipple is the projecting part of the mammary gland.

Answer 190

c ## Footnote Like mammals, birds like chicken, have a heart with 4 chambers (right atrium, right ventricle, left atrium and left ventricle).

Answer 191

b ## Footnote Pigs and horses lack the acromial part of the deltoideus muscle. Remember that in their scapula, they lack the acromion and the spine fades distally.

Answer 192

a ## Footnote Chicken “tenders” are the supracoracoideus muscle of that domestic fowl. It is antagonistic to the pectoralis and provides the upstroke when the bird is flying.

Answer 193

c ## Footnote Cleidocephalicus can be divided based on their insertion at the head (cleidooccipitalis – occipital bone; cleidomastoideus – mastoid process of the temporal bone). This division is present in most domestic animals except in horse in which it is undivided and inserted only at the mastoid process of the temporal bone (cleidomastoideus).

Answer 194

b ## Footnote Dental alveoli (singular alveolus) are sockets in which the roots of teeth are held in the alveolar process with the periodontal ligament. Ruminant dentition is unique because they lack the upper incisors and is replaced by the dental pad. This means that the teeth of the upper dental arcade are attached to the maxillary bone only, while the teeth at the lower dental arcade are attached to the mandible.

Answer 195

b ## Footnote The tendon of Achilles is a common tendon formed by the tendons of the gastrocnemeus and superificial digital flexor muscles. It is attached to the talus or the fibular tarsal bone.

Answer 196

b ## Footnote Birds have left and right lungs positioned dorsally, to the left and right of the vertebral column. Their lungs are not divided into lobes. The rest of the statements are correct.

Answer 197

b ## Footnote The lateral plate mesoderm develops into the circulatory system (including the heart and spleen).

Answer 198

b ## Footnote Mammalian colon is divided into three segments: ascending, transverse and descending colon. Most of the modification used in comparing domestic animals can be seen at the ascending colon (dog being simple and short, horse having horse-shoe shape, ruminants and pig with spiral loops). Note that birds lack colon.

Answer 199

a ## Footnote Hematopoietically active bone marrow is most consistently found in the flat bones (sternum, ribs, pelvis, vertebrae) and proximal ends of long bones (humerus, femur). The ribs are one of the preferred sites for bone marrow aspirates in cattle. The dorsal ends of ribs 8 to 11 can be accessed for sequential aspirations.

Answer 200

a ## Footnote Birds, like chicken, have only one occipital condyle unlike mammals with 2. This feature enables bird to rotate their head at a greater degree than mammals.

Answer 201

a ## Footnote Large ruminant kidneys are lobated like a bunch of grapes and lack renal pelvis. Formed urine directly move from minor to major renal calyces then to the ureter without the renal pelvis.

Answer 202

a ## Footnote The two proximal sesamoid bones are seen at the palmar side of the metacarpophalangeal joint while the distal sesamoid bone is seen on the dorsal side of the same joint.

Answer 203

d ## Footnote The upper dental arcade is composed of teeth attached both to the maxillary bone (canines, molars and premolars) and incisive bone (incisors). The lower dental arcade is composed only of teeth attached to the mandible.

Answer 204

b ## Footnote Oligodendrocytes are a type of glial cell found in the CNS. They are responsible for the production and maintenance of myelin, a fatty substance that forms an insulating layer around axons, the long projections of neurons. Myelin is formed by Schwann cells in the peripheral nervous system (PNS). Ependymal cells are specialized epithelial cells that line the ventricles of the brain and the central canal of the spinal cord. They are involved in the production and circulation of cerebrospinal fluid (CSF). Astrocytes are a subtype of glial cells that make up the majority of cells in the CNS. They perform metabolic, structural, homeostatic, and neuroprotective tasks such as clearing excess neurotransmitters, stabilizing and regulating the blood-brain barrier, and promoting synapse formation.

Answer 205

d ## Footnote Reptiles depend entirely on their lungs for respiration. The diaphragm is absent in all reptiles, with the exception of crocodiles. They have diaphragm that can facilitate breathing. Snakes, which lacks diaphragm use their ribs during breathing. In between each rib are muscles — primarily the levator costa muscles — which help the ribs contract the lungs, forcing air in, and then letting air out when the ribs relax. Lizards do not have a diaphragm; instead, their chest muscles move the chest wall, which inflates and deflates the lungs. A few lizard species use their throat muscles to “gulp” air in a process called buccal pumping (a process also used by amphibians). Turtles have lungs but their shells don't allow their ribcages to expand and contract. Instead of a diaphragm, they have muscles lining the inside of their shells to help push air in and out.

Answer 206

b ## Footnote Lymph node is missing in birds.

Answer 207

d ## Footnote The hamstring group of muscles includes the biceps femoris (lateral), semitendinosus (middle) and semimembranosus (medial). These are the superficial muscles of the hip and thigh and attach proximal and distal to the stifle joint.

Answer 208

c ## Footnote Meckle's diverticlum is a small pouch-like structure between the jejunum and ileum of birds. It is a remnant of the yolk sac.

Answer 209

a ## Footnote Philtrum is a deep median goove in the planum nasale of dog and small ruminants. It is absent in pig (with planum rostrale), large ruminant (with planum nasolabiale) and horses. This structure is very distinct in sheep.

Answer 210

a ## Footnote Female birds have a sperm host gland. This structure is found at the uterovaginal junction where sperm can be stored for many months.

Answer 211

a ## Footnote Among the choices, only male dog lacks bulbourethral gland.

Answer 212

a ## Footnote Normally, the parenchymatous zone, where the follicles are seen, is located at the cortex while the vascular zone, composed of the blood vessels, is located at the medulla. This pattern is true for most of domestic animals. However, the ovary of mare is different from the rest because of the reverse arrangement of the parenchymatous and vascular zone.

Answer 213

d ## Footnote Horse has a bulbourethral gland. It looks like a walnut. The rest of the choices about the horse male reproductive tract are correct.

Answer 214

a ## Footnote In horse and in pig, the right coronary artery gives rise to the subsinousal interventricular branch. In dogs and ruminants, the left coronary artery gives rise to both paraconal and subsinousal interventricular branches.

Answer 215

d ## Footnote Pigs have a structure called pharyngeal diverticulum located above the opening of esophagus and can be mistaken as esophagus when pilling pigs.

Answer 216

a ## Footnote The magnum is approximately 30 cm long and is the longest segment of the female bird’s reproductive tract.

Answer 217

a ## Footnote The cutaneous trunci is a thin sheet of muscle that covers most of the dorsal, lateral, and ventral walls of the thorax and abdomen. In the male dog, there is a distinct development of this muscle adjacent to the ventral midline caudal to the xiphoid. This is the preputial muscle, which supports the cranial end of the prepuce during the nonerect state and to pull the prepuce back over the glans penis after erection and protrusion.

Answer 218

a ## Footnote The muscles of the tongue include the styloglossus, hyoglossus, genioglossus, and lingual intrinsic muscles. The other choices are muscles of the hyoid apparatus and pharynx.

Answer 219

b ## Footnote The muscles of the tongue include the styloglossus, hyoglossus, genioglossus, and lingual intrinsic muscles. Styloglossus – extends from the stylohyoid to the tongue. It has three muscle heads that inserts at the tongue at different level. It draws the tongue caudally. Genioglossus- thin, triangular muscle at the intermandibular space ventral to the tongue. Contraction draws the entire tongue rostrally. It depresses the tongue. Hyoglossus – located at the root of the tongue. It retracts and depresses the tongue.

Answer 220

c ## Footnote The third aortic arch is one of the six pairs of aortic arches that form the arterial system of the developing embryo. Specifically, the third aortic arch gives rise to the proximal portion of the internal carotid artery, which is a major artery that supplies blood to the brain and other structures in the head and neck region.

Answer 221

b ## Footnote Type II alveolar cells are described to be cuboidal in shape. Type II alveolar cells, also known as Type II pneumocytes, are one of the two main types of cells that make up the alveoli in the lungs. They are responsible for producing and secreting a substance called surfactant, which helps to reduce the surface tension of the alveoli and prevent their collapse during expiration.

Answer 222

b ## Footnote Myeloid cells include monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, and megakaryocytes to platelets. Lymphoid cells include T cells, B cells, natural killer cells, and innate lymphoid cells.

Answer 223

b ## Footnote The floor of the cranium is formed by the sphenoid bone together with the basilar part of the occipital bone. The cornual process is a body process at the frontal bone of horned ruminants. This is missing in polled ruminants. The temporal bone forms the lateral wall of the cranium while the parietal bone, together with the frontal bone, forms the roof of the cranium.

Answer 224

b ## Footnote There are two distinct hepatic lobes present in chicken - the left and the right lobes. The gall bladder is situated at the right lobe of their liver.

Answer 225

a ## Footnote In chicken, there is only one pulmonary vein. This is in contrast with domestic mammals with more than one pulmonary vein.

Answer 226

b ## Footnote Ideally, bronchi are expected to be seen at the bifurcation of the trachea. However, in cattle and in pig, additional bronchus can be located at the right side of the trachea distant from the bifurcation. This is called the tracheal bronchus.

Answer 227

a ## Footnote Archenteron is the rudimentary alimentary cavity of an embryo at the gastrula stage.

Answer 228

a ## Footnote Floating is the removal of sharp points from the cheek side of the horses' teeth. This fixes misalignment or sharp edges that have developed. Occlusal surface or masticatory surface – surface that faces the ipsilateral opposite upper and lower arch. This surface allows contact of teeth between the lower and upper dental arcade. This is the one being filed off during floating. Vestibular surface – surface of teeth that faces the lip or cheek, formerly called labial or buccal surface. Lingual surface – surface of the teeth that faces the tongue Contact surface – surface of the teeth that faces the adjacent teeth in the dental arch. Mesial surface is the contact surface adjacent to the next rostral or medial tooth, and the distal surface is the contact surface adjacent to the next caudal or lateral tooth.

Answer 229

a ## Footnote Among the choices, only the bull has a fibroelastic-type of penis. The rest are of vascular-type.

Answer 230

b ## Footnote The restraining method described is the best restraint done when the cephalic vein is used as a venipuncture site.

Answer 231

c ## Footnote The surface ectoderm will give rise to the epidermis and then to the external glands, hair, claws, and skin glands. The endocrine glands that produce the steroid hormones, such as the gonads and adrenal cortex, arise from the mesoderm.

Answer 232

c ## Footnote Thymus, originally, is composed of cervical and thoracic parts. However, in horses, cervical part regresses prematurely and the thymus is represented by the thoracic part only.

Answer 233

b ## Footnote A feather has a hollow and rigid shaft. The calamus or quill is the hollow portion of the shaft of the feather. The rachis is the rigid shaft. The term remiges denote the flight feathers while the barbs are structured that grow from the rachis. Barbs form the vane of the feather.

Answer 234

b ## Footnote Reticulum is also known as the honeycomb of the ruminant forestomach because of the presence of internal ridges.

Answer 235

b ## Footnote Hock is a joint at the hindlimb formed by the distal end of the tibia and the proximal rows of the tarsal bones. The hock is an important weight-bearing joint in horses, enabling movement, flexibility, and propulsion during activities such as walking, running, jumping, and turning.

Answer 236

c ## Footnote Birds have either protrusible (duck) or non-protrusible (chicken) phallus. This is a spiral structure that serves as their copulatory organ.

Answer 237

b ## Footnote The claw plate is analogous to the hoof wall in ungulates. It is a modified epidermis that covers the ungual process and other underlying structures. The ungual crest and ungual process are bone parts of the third phalanx. The claw fold is a fold of epidermis that covers the proximal portion of the claw plate, like the periople in the hoof.

Answer 238

b ## Footnote The levator palpebrae superioris muscle lifts the upper eyelid, while the orbicularis oculi muscle closes the eyelids when blinking. The frontalis muscle supports the upper eyelid and keeps it open, while the dorsal rectus muscle depresses the eye.

Answer 239

c ## Footnote Birds, unlike mammals, have a complete tracheal rings. In mammals, the tracheal rings are completed by the trachealis muscle.

Answer 240

c ## Footnote In most cases, the digestive tract lining is composed of simple columnar epithelium. The duodenum is a segment of the intestine and responsible for absorption of nutrients thus it has to be columnar in structure.

Answer 241

b ## Footnote There are two main cell types that are involved in dental tissue formation: the ameloblasts, of epithelial origin, that form enamel, and the odontoblasts of mesenchymal origin, which are responsible for dentin production.

Answer 242

a ## Footnote From the name itself, urodeum is the part of the cloaca where the urine enters directly from the ureter.

Answer 243

c ## Footnote The ungual process in carnivores is the distal part of the distal phalanx. It is a curved extension of the distal phalanx into the claw.

Answer 244

c ## Footnote Buccinator acts to flatten the cheeks, pressing the food between the teeth, as well as to retract the angle of the mouth.

Answer 245

a ## Footnote Splenic lymph node is a part of the coeliac lymphocenter. The rest of the choices are part of cranial mesenteric lymphocenter.

Answer 246

c ## Footnote In terms of mammary gland position, dogs are classified to have a thoracoabdominoinguinal. This means that the mammary gland extends from the inguinal up to the thoracic area. Note that are usually a total of 10 mammae in dogs.

Answer 247

b ## Footnote Four fetal membranes develop in a conceptus. Two arise from the trophoblast layer of the blastocyst (and are continuous with the somatopleure of the embryo). Two arise from the inner cell mass of the blastocyst (and are continuous with splanchnopleure of the embryo). 1. Chorion - forms the outer boundary of the entire conceptus (from trophoblast). 2. Amnion - encloses the embryo within a fluid-filled amnionic cavity; formed by folds of the chorion in domestic mammals. 3. Allantois - is highly vascular and provides the functional vessels of the placenta, via umbilical vessels. 4. Yolk sac - continuous with midgut splanchnopleure (develops early with hypoblast formation from inner cell mass). Supplied by vitelline vessels, it forms an early temporary placenta in the horse and dog. Yolk sac is most important in egg-laying vertebrates.

Answer 248

a ## Footnote Paranasal sinuses are a group of complex cavernous air-filled spaces, lined by respiratory epithelium, which develops by evagination of the nasal mucosa into spongy bone. At a certain age of calves, horns become attached to the frontal bone of the skull. Frontal paranasal sinus lies within the skull beneath the horn bud. As the horn grows and attaches to the skull, this frontal sinus joins into the adjacent portion of the horn. Thus, calves should be dehorned before 4 months.

Answer 249

c ## Footnote Sow’s uterine horn looks like the small intestine because they are extremely long and flexuous (having a lot of curves).

Answer 250

c ## Footnote Gemelli is located at the proximal part of the femur thus the sciatic nerve innervates it.