Page 41 - Differential Diagnosis in Small Animal Cytology, The Skin and Subcutis

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Dermis
VetBooks.ir The dermis contains collagen, elastic fibres, blood vessels, sensory structures and fibroblasts. It
can be subdivided into:
Superficial dermis
•
It supports the upper portion of the hair follicles and the sebaceous glands.
• Deep dermis
It contains the lower part of the hair follicle and the apocrine (sweat) glands.
Subcutis
The subcutis contains adipose tissue, collagenous and elastic fibres and blood vessels. It attaches
the dermis to the underlying muscle layer or bone.
Adnexa
There are different types of adnexa:
• Sebaceous glands
Their ducts open into the hair follicle except for the sebaceous glands located at the mu-
cocutaneous junctions, which open on the surface of the skin (e.g. Meibomian glands).
• Sweat glands
These are of two main types:
• Apocrine glands are scattered throughout the haired portions of the skin. Their duct
opens on the superficial portion of the hair follicle.
• Eccrine glands are mostly located in the paw pads in dogs and cats. Their duct opens
directly on the surface of the epidermis.
• Specialized structures
• Anal sacs are composed of:
• Sac wall and apocrine cells in dogs. Ducts and sacs are lined by stratified squamous
epithelium.

Infundibulum

Sebaceous
gland
Isthmus
Arrector pili
muscle
Inferior segment

Fig. 5.2. Sections of a hair follicle.