Glands of paranal sinus

The glands of the paranal sinus are typically divided into two main types:

a) Sebaceous glands

• Located near the opening of the duct.

• Produce lipid-rich secretions.

• Lined by simple cuboidal to stratified squamous epithelium.

b) Apocrine glands

• Located deeper in the wall of the anal sac.

• Produce a more watery secretion, often odorous.

• Their secretions contribute to chemical communication (pheromonal signaling).

These glands secrete into the lumen of the anal sac, and the secretions are expressed during defecation or when the animal is frightened.

3. Species Differences

a) Dog

• Well-developed anal sacs.

• Prominent apocrine glands associated with each sac.

• Prone to impaction, infection, and neoplasia.

b) Cat

• Anal sacs are smaller than in dogs.

• Apocrine and sebaceous glands are present, but secretion is less copious.

• Clinical problems are less frequent than in dogs.

c) Ruminants (Cattle, Sheep, Goats)

• Do not have paranal sinuses or anal sacs.

d) Horse

• Do not have anal sacs.

e) Pig

• Have paranal sinuses, but not as prominent as in dogs or cats.

• Glands may be rudimentary.

f) Carnivores (e.g., ferrets, wild carnivores)

• Very developed anal sacs and associated glands.

• Used for territory marking and defense (e.g., skunks).

4. Clinical Relevance

• Impaction: Common in dogs due to thickened secretions or ductal obstruction.

• Abscessation: May rupture and cause perianal fistulas.

• Neoplasia: Apocrine gland adenocarcinoma is a known condition in dogs.

Differences between circumanal glands and glands of paranal sinus (paranal glands)