Multiple Choice Questions (MCQ) on Veterinary Anatomy and Histology (Part-3)

ANSWERS & EXPLANATIONS

1.

a. (Iris) - Iris is the vascular tunic of eye.
Eyeball is the chief apparatus for vision, comfortably housed in the orbit within a soft atmosphere of surrounding fat, composed of three coats - Fibrous, vascular and nervous coat and its contents are aqueous humour, vitreous humour and lens.

Fibrous coat:

Outer protective hard coat of eyeball, where opaque posterior fifth sixth part- sclera (composed of white fibrous tissue intermixed with elastic fiber, externally white in color while internal surface is brown, having groove; posteriorly it is pierced by optic nerve (just medial to the posterior pole at the optic disc or blind spot of eye), ciliary nerve and vessels. The area has an appearance of cribriform plate, known as lamina cribrosa sclerae, this lamina transmits central retinal vessels along with nerve bundles. Suprachoroidal lamina, layer between sclera and choroid. Within sclera and cornea junction, an encircling canal or sinus located, known as canal of Schlemm or Sinus venosus sclera. Internally, there is projected rim of scleral tissue behind canal, known as scleral spur. Aqueous humour, pass from anterior chamber to canal, ultimately to venous system through anterior ciliary vein. and anterior transparent one sixth - cornea, convex in front and concave behind, composed of corneal epithelium, anterior limiting membrane, substantia propria, posterior limiting membrane, and endothelium of anterior chamber. One of refracting media of eye.

Vascular coat:

It lies between sclera and retina, consists of choroid, ciliary body, and iris. Choroid - dark colored thin vascular membrane, composed of capillary plexus, small blood vessel, and loose CT, contains pigment cells. Note: Choroid of nocturnal habit animal, contain reflecting structure, the tapetum, gives greenish glare at night. Ciliary body- Anterior thickened part of choroid (thickening due to presence of raised ridges- ciliary process. there are fine fibers extend from ciliary process to capsule of lens, maintain position of lens, known as suspensory ligament. Iris is the anterior continuation of vascular tunic, suspended in aqueous humour behind cornea and Infront of lens. Cental aperture of iris - pupil.

Nervous coat:

Innermost tunic composed retina. Retina is actually membranous expansion of optic nerve elements, composed of nervous tissue, blood vessel, pigment cells and modified CT, arranged in 10 conventional layer- Pigment cell layer, layers of rod and cones, External limiting membrane, External nuclear layer, External plexiform layer, Internal nuclear layer, Internal plexiform layer, Ganglionic cell layer, layer of nerve fiber and internal limiting membrane. At the center of the posterior pole of eyeball, the retina presents an oval yellow spot- macula lutea. At middle of macula lutea, there is depressed area named fovea centralis, in which sense of vision is more acute (retina is very thin).

2.

b. (Temporal) - Middle Ear is located in temporal bone.
Ear is the organ, associated with hearing and equilibrium, composed of three parts - External Ear, Middle Ear and Internal Ear.

External Ear:

It divided into two portion- Pinna or Auricle (roughly an elongated funnel shaped structure, having two surfaces - anterior (possess an opening of external ear) and posterior surface (Covered by hairy skin), composed of 3 cartilages (Conchal, Scutiform and Annular) and External Acoustic meatus- canal which leads medially towards middle ear, lining epithelium of acoustic meatus accommodates some sebaceous and sweat gland which secretes cerumen or ear wax. Border of External and Middle Ear - Tympanic membrane (Ear Drum - believed to be derived from all three layers- Ectoderm, Mesoderm and Endoderm).

Middle Ear (tympanic cavity):

Irregular, biconcave small space within petrous temporal bone, contains ear ossicles (Malleus- hammer shaped bone; Incus- anvil shaped bone; stepes- stirrup shaped bone; part of chorda tympani (branch of facial nerve), muscles and air. The anterior wall presents the opening of canal which lodges tensor tympani muscles and another opening of Eustachian or auditory tube, which maintains atmospheric pressure in middle air by its communication with pharynx.

Internal Ear:

(Main portion of organ of hearing and situated within petrous temporal bone, consists of osseous labyrinths and membranous labyrinths, space between two labyrinths is filled with fluid, known as perilymph (resembles CSF). Body labyrinths comprises of:
a. Vestibule: Bony cavity medial to tympanic cavity, continues with cochlea infront and semicircular canal behind (attached by five orifices to posterior part of vestibule), lodges utricles and saccule of membranous labyrinth.
b. Cochlea: bony spiral canals winds two and half turns, and has appearance of a shell of snails
c. semicircular canal: Curved tube (3 in number - anterior, posterior and lateral), terminal part of tubes at their junctions with vestibule are dilated to form Ampullae.
Membranous Labyrinths: It includes Cochlear duct (membranous cochlea is formed by basilar membrane), saccule and utricles (Utricle is larger than saccules, communicates each other by utriculosaccular duct) and three ducts of semicircular canal (same shape as osseous semicircular canal). Cavity of membranous labyriths is filled with endolymph.
Organ of Corti: (Sense organ of hearing, situated on basilar membrane, contains hair cells, tunnel of corti, tectorial membrane and spiral ganglion.

3.

b. (Cattle): Syndesmochorial placenta is seen in cattle.

Classification of Placenta

Species	Gross Shape of Placenta	Microscopic Structure	Loss of Materal tissue at Birth
Mare and Sow	Diffuse	Epitheliochorial	Non - deciduate
Ruminant	Cotyledonary	Syndesmochorial	Non - deciduate
Dog and Cat	Zonary	Endotheliochorial	Deciduate
Human and Monkey	Discoidal	Haemochorial	Deciduate

4.

b. (Allantois)
Urine is stored temporarily in the fetus in Allantois membrane.
Fetal membranes: Membranous structures, surrounding embryo during its developmental period, includes amnion, chorion, allantois, yolk sac and umbilical cord, develops from the zygote.
Such membranes are external to embryo proper, called extraembryonic membranes, functions in the embryo’s protection, nutrition, respiration and excretion. Chorion and Amnion do not take part in formation of embryo or fetus while part of yolk sac incorporates into embryo as primordium of gut and allantois formed a fibrous cord called urachus.
Chorion - Outermost fetal membrane
Amnion- Innermost fetal membrane (makes a hydrostatics cushion around embryo and provides a protective environment for the developing fetus.
Allantois- lies between amnion and Chorion (helps the embryo to exchange gases and takes up nitrogenous waste especially urine from the fetus.

5.

d. (Digestive system)
-Meckel’s Diverticulum occurs in the fetus early in the pregnancy, normally vitelline duct, which connects the growing fetus with the yolk sac, is absorbed into the fetus normally. When the vitelline duct is not fully absorbed, a Meckel’s diverticulum develops.
Meckel’s diverticulum is true congenital diverticulum, is a slight bulge in the SI.
Meckel’s diverticulum is most commonly found in Horse and Swine.

6.

d. (Testis): Testis is derived from Mesoderm.

Derivatives of organs from three Germinal layers

Endoderm	Mesoderm	Ectoderm
-GI tract from pharynx to upper rectum -liver, Pancreas, - Respiratory epithelium-Middle ear-Urinary bladderThyroid parathyroid	-Muscles - Bone and connective (Except in head) -Urinary system Reproductive system-Circulatory system -Dermis (Except head and neck) - Adrenal cortex	- Nervous system - Bone and CT in head - Dermis in head and neck -Adrenal medulla -sensroy organ Epidermis ‘- Mammary gland -penile urethra

7.

a. (Eustachian tube); Eustachian tube is derived from 1st pharyngeal Pouch

Derivatives of the Pharyngeal Pouches

Pharyngeal Pouches	Derivatives
1	Tympanic or Middle Ear Cavity Eustachian tube
2	Palatine tonsil Tonsillar fossa
3	Inferior Parathyroid gland Thymus
4	Superior parathyroid gland Ultimobranchial body (parafollicular cells of the thyroid gland)

8.

b. (Fungiform papillae); Taste buds are found in Fungiform papillae.
Tongue is highly movable muscular structure for prehension, mastication and deglutition. Also plays important role in tastes, situated on the floor of the mouth, between the two rami of lower jaws, has a root, body and apex
Tongue is composed of pigmented mucus membrane, muscles, glands, vessels and nerve. A fold of mucus membrane which connects the ventral surface of tongue with floor of mouth - Frenum linguae.
The dorsal surface of tongue contains variety of papillae - Filiform, Fungiform, lenticular and vallate. Among all papillae, Fungiform papillae bears taste buds.
A taste bud has an oval body, neck and a taste pore, comprises supporting cells and taste cells.

9.

d. (Sheep)
Kidney of Cattle, Buffalo, Bull - Lobulated and bean or roughly oval shaped
Kidney of Sheep and Goat- Bean shaped and smooth
Horse: Right - heart shape and left - bean shaped, surface- smooth
-Dog cat, rabbit: Bean shaped and smooth
-Pig: Bean shaped and lobulated
-Fowl: Elongated and lobulated

10.

c. (Thymus)
Hassall’s corpuscles (thymic corpuscles) are structures found in the medulla of thymus, formed from eosinophilic type VI epithelial reticular cell arranged concentrically.

11.

b. (7); The number of paired pronephric tubules are seen in the early part of the development of kidney are about 7 pairs.
Embryonic development of kidney:
-Kidney is developed from intermediate mesoderm, portion of this mesoderm that condense to give kidney are nephrogenic cords.
Three stages of development:
Pronephros: Number of paired pronephric tubules/duct seen in early development - 7 pairs
Mesonephros: Number of paired mesonephric tubules/duct in early part of development - 30 pairs
Metanephros: permanent kidney is formed.
Certains Anomalies:
Horseshoe kidney: Due to the fusion of the metanephric primordia the two sides lead to anomaly, horseshoe appearance of kidney.
-Cystic kidney: Blockage of urine where there is failure in the communication between secretary and excretory tubules in development of kidney
Pelvic kidney: Anatomical defects where kidney fails to rise their normal position during embryological development.
-Forked ureter (Duplex kidney): Another anomaly where two ureter draining urine from a single kidney.

12.

d. (Uterus masculinus)
-Uterus Masculinus: The portion which forms uterus and vagina from the mullerian duct persists in a male in a rudimentary form - Uterus Masculinus.
Collicus seminalis: It is rounded prominence situated distal to the entrance of the ejaculatory ducts.
Mesonephric duct/Wolffian duct - Male reproductive system while paramesonephric/ mullerian - female reproductive duct.

13.

a. (Epoophoron)
The cranial group of mesonephric tubules in female persists as Epoophoron.
Epoophoron is a rudimentary organ homologous with the male epididymis that lies in the broad ligament of the uterus.
Paroophoron: A group of rudimentary tubules in the broad ligament between the epoophoron and the uterus that constitutes a remnant of the lower part of the mesonephros in female corresponding to paradidymis of male.
Gartner’s canal: Embryologic remnants of the Wolffian (mesonephric) duct.

14.

a. (Omentum)
The double fold of peritoneum passing from stomach to other viscera is termed as Omentum
The double fold of peritoneum attaches intestine to the wall of the abdomen is mesentery
Ligaments - The double fold of peritoneum attaches viscera other than parts of digestive tracts to the wall of the Abdomen
Lesser omentum - The double fold of peritoneum extending from liver to the parietal surface of omasum
Greater omentum -The double fold of peritoneum extending from greater curvature of stomach to the transverse colon
Sacro rectal - The peritoneum is reflected and form a pouch between rectum and sacrum

15.

b. (Reticulum)
Interior Surface of:
Rumen: Towel like appearance
Reticulum: Honeycomb
Omasum: Multiple folds are present (Ladies’ purse)
Abomasum: Smooth surface (Glandular) (True Stomach)

16.

b. (Abomasum)
Saccus caecus is the region in oesophagus at the entrance of stomach where food first comes in contact with HCL in equine.

17.

c. (Horse)
Margoplicatus is a line separates non glandular and glandular part in the stomach of Horse.
The horse’s stomach contains two different types of surfaces: the non-glandular, squamous mucosa on the top half, pale pink and shiny and the glandular mucosa on the bottom half, darker in color, contains the stomach acids producing cells.
Gastric ulcer can occur in either location, but the most common along the join in the different surfaces of stomach, the margoplicatus or in the squamous portion.

18.

d. (Lesser Curvature)
Ileo- Caecal and Caeco- Colic orifice is present in the lesser curvature of caecum of horse.

19.

b. (Horse)
The Scythe shaped (roughly triangular) spleen is present in Horse.
The Oyster Shell shaped spleen is present in Sheep.
Elliptical shaped spleen is present in Cattle
Human footprint shaped spleen is present in Dog
-Elongated and Spatula shaped spleen is present in Rabbit
-Small round reddish-brown spleen is present in Fowl.

20.

a. (Arytenoid)
Larynx is the elongated Musculo- cartilaginous structure situated between pharynx and trachea, consists of following cartilages:
a. Thyroid cartilage: Largest of the four (Shield shaped)
b. Cricoid cartilage: Signet ring shaped cartilage
c. Arytenoid cartilage: Paired cartilage
d. Epiglottis: Leaf or plate like structured cartilage.

21.

c. (Sandwich model)
-Davson and Danielli describe the cell membrane as Sandwich model.
David Robertson gives Unit membrane model of cell membrane.
Singer and Nicolson proposed Fluid Mosaic model.

22.

c. (Acrocentric)
Classification of Chromosomes on the basis of position of Centromeres
a. Metacentric chromosome: A chromosome having Centromere at the centre
b. Sub metacentric Chromosomes: A chromosome having centromere slightly away from the centre.
c. Acrocentric chromosome: A chromosome having centromere close to one of the ends.
d. Telocentric chromosome: A chromosomes having a terminal centromere.

Note:

For video: https://youtu.be/UDND0axrmEA

Since it's a part 3, for mcq on veterinary anatomy part-4: Multiple Choice Questions on Veterinary Anatomy and Histology (Part-4) - Vet Lectures (veterinarylectures.com)

For mcq on Veterinary Anatomy, part- 2: Multiple Choice Questions on Veterinary Anatomy and Histology (Part -2) - Vet Lectures (veterinarylectures.com)