Veterinary Anatomy and Physiology Flashcards

In ruminants, the omasum performs which of the following functions that distinguishes it most from the reticulum?

Answer: Absorption of water and electrolytes while grinding ingesta between laminae

The omasum (third stomach compartment) is lined with muscular laminae (leaves) that grind and compress ingesta, and its epithelium actively absorbs water, sodium, and potassium. The reticulum is responsible for mechanical sorting and the reticular groove reflex. Fermentation occurs primarily in the rumen. Intrinsic factor in ruminants is secreted by the abomasum.

Which of the following best describes the unique hemodynamic arrangement of the feline renal portal system compared to dogs?

Answer: Cats have an incomplete renal portal system that shunts a variable proportion of caudal venous blood through the renal tubular capillaries

Unlike birds, which have a true renal portal system routing hindlimb venous blood through renal tubular capillaries before the systemic circulation, cats have an incomplete/vestigial system with valve-controlled partial diversion. This is clinically relevant because drugs eliminated renally can be taken up by tubular cells from either arterial or portal blood. Dogs lack this system altogether.

A horse presents with symmetric ataxia and weakness in all four limbs, with hindlimbs more severely affected. Necropsy reveals demyelination and axonal degeneration most concentrated at the cervical intumescence. Which region of the spinal cord contains the neuronal cell bodies whose axons project to the forelimb musculature and would be most directly damaged in this region?

Answer: Ventral horn of C6–T2

The cervical intumescence (C6–T2 in horses) contains the lower motor neuron cell bodies in the ventral horn whose axons form the brachial plexus and innervate forelimb musculature. Damage here produces LMN signs in the forelimbs. Clarke's nucleus relays proprioception. The intermediolateral column provides preganglionic sympathetic innervation. The dorsal horn processes sensory input.

During the avian respiratory cycle, in which phase does air flow through the parabronchi of the bird lung, and in which direction does blood flow relative to this airstream?

Answer: During both inspiration and expiration; blood flows countercurrent (crosscurrent) to airflow

Birds have a flow-through lung: fresh air passes through the parabronchi during BOTH inspiration (from caudal air sacs) and expiration (from cranial air sacs), providing unidirectional airflow. Blood in the parabronchial capillaries flows at right angles (crosscurrent) to the airstream, maximizing O2 extraction efficiency — allowing birds to maintain oxygenation at high altitudes where mammals would fail.

In the equine foot, the deep digital flexor tendon (DDFT) inserts on the flexor surface of the distal phalanx. Which bursa lies between the DDFT and the navicular bone, and what is its direct communication with the distal interphalangeal joint in most horses?

Answer: The navicular bursa (podotrochlear bursa); it communicates directly with the distal interphalangeal joint in approximately 20–25% of horses

The navicular (podotrochlear) bursa is interposed between the DDFT and the navicular bone (distal sesamoid). It communicates with the distal interphalangeal joint (coffin joint) in approximately 20–25% of horses, which is clinically significant because infection of one structure can spread to the other. This is why navicular bursa injuries are especially serious — joint involvement dramatically worsens prognosis.

In the male dog, the bulbus glandis engorges during copulation to create a 'tie' with the female. Which erectile tissue type composes the bulbus glandis, and how does it differ from the corpus cavernosum penis in terms of venous drainage control?

Answer: The bulbus glandis is composed of corpus spongiosum tissue with a prominent tunica albuginea; venous drainage is occluded by contraction of the bulbospongiosus muscle compressing emissary veins

The bulbus glandis is an expansion of the corpus spongiosum (pars longa glandis surrounds the urethra, while the bulbus glandis flanks it proximally). Unlike the corpus cavernosum penis (which has a rigid tunica albuginea enabling high-pressure erection), the bulbus glandis has its own tunica and depends primarily on bulbospongiosus muscle activity compressing emissary veins to maintain engorgement. This sustained muscular compression is what makes the copulatory tie functionally possible for 15–30 minutes.