Human hair does not have much protective value. Eyelashes, eyebrows, and ears and nostril hairs have obviously useful functions, and scalp hair can provide some protection from the Sun. It also has other functions like sensory input and thermoregulation.

2. SKIN: It is the largest single organ of the body. Also known as the integument or cutaneous layer, the skin is composed of:

– EPIDERMIS is an epithelial layer of ectodermal origin. It protects against friction and water loss.

– DERMIS is a layer of mesodermal connective tissue. It houses nerve endings, blood vessels, oil and sweat glands, and hair follicles. Moreover, its composition of connective tissue provides elasticity to the skin.

– Beneath the dermis is the hypodermis or subcutaneous layer, which is not considered part of the integument. It is composed of areolar and adipose connective tissue

3. SWEAT GLANDS: It is an EPIDERMAL APPENDAGE. Sweat glands develop as long epidermal invaginations embedded in the dermis. There are two types of sweat glands, eccrine and apocrine, with distinct functions, distributions, and structural details.

– ECCRINE sweat glands are widely distributed in the skin and are most numerous on the foot soles. It provides an important mechanism for cooling the body.

– APOCRINE sweat glands are largely confined to skin of the axillary and perineal regions. Their development depends on sex hormones and is not complete and functional until after puberty.

The secretory components of apocrine glands have much larger lumens than those of the eccrine glands. The drawing is representative of the ECCRINE SWEAT GLAND as the lumen is narrow.

References:

Mescher, A. L., & Uchôa, J. L. C. (2018). Junqueira’s basic histology: Text and Atlas. McGraw-Hill Education.

Internet sources:

https://www.britannica.com/science/human-skin/Hair

Hair