LESSON 28 cortas Langerhans Cells and Antigen Presentation Quiz

The integumentary system is composed of the skin (epidermis, dermis, hypodermis), skin appendages (glands, hair follicles, and hairs), and related structures such as hooves, horns, claws, nails, comb, and beards.

The skin is made up of three layers: the epidermis (an epithelial tissue), the dermis (a connective tissue), and the hypodermis (subcutaneous tissue, which is a loose connective tissue and adipose tissue).

The thickness of the skin decreases dorso-ventrally and cranio-caudally. The areas with the greatest skin thickness are the forehead and the dorsal area of the neck, the thorax and the hip, and the thinnest are the ear pinna and the axillary, inguinal, and perianal areas.

Almost the entire skin surface of domestic animals is covered by hair, wool, or feathers.

Langerhans cells in the epidermis phagocytose antigens and travel to regional lymph nodes to present antigens to specific lymphocytes, stimulating the immune response.

Merkel cells are neuroendocrine cells located in specific regions like whiskers, tactile hairs, footpads, and oral mucosa, connected to nerve fibers, forming Merkel cell-neurite complexes.

The dermis is fibrous connective tissue with a network of collagen and elastic fibers, divided into papillary and reticular layers.

The hypodermis is composed of fibrous connective tissue with adipose tissue (fibroadipose tissue) and functions as a layer of insulation and energy storage.

Sebaceous glands are exocrine glands that produce sebum in a holocrine secretion and discharge it to the hair follicle, with two types of cells: basal and secretory.

Apocrine sweat glands are coiled tubular glands with serous secretion and cooling function, abundant in canids and equids. Eccrine sweat glands are tubular glands with merocrine secretion and are found in various body parts.

Hepatoid glands are exocrine glands located around the anus, in the perineum, and in the buttock of the tail of canids, with lumen-free secretory units, and have a tendency to neoplastic transformation in males.

The mammary gland is a modified exocrine cutaneous sweat gland that produces milk in an apocrine form, with secretory units and ducts of columnar to cuboidal epithelium.

The hair follicle is a tubular invagination of the epidermis and basement membrane into the dermis, covered by the epidermis, with a structure composed of layers such as the basement membrane, external and internal root sheaths, and hair shaft.