Physiology Topics
Hair is an epidermal derivative, made of keratinized cells (hair keratin is different from skin keratin). The hair bulb contains several layers. The cortex layer (second layer from the central axis) is missing in thin hair or due to aging, and may be replaced with air bubbles. At the bulb, the outermost epidermal layer of the hair is followed by a dermal layer.
There are two types of skin hair: vellus hair (mostly found in women, children and the elderly) and coarse hair (mostly found in men).
Age-related hair loss is due to lost hair follicles. Male-pattern baldness is due to premature shading of hair, that is overactive follicles. This condition is worsen by high levels of testosterone.
Hair color is taken from melanocytes at the end of the hair follicle. Gray hair is due to the absence of pigment. White hair is due to air bubbles inside the matrix.
Several structures are associated with the hair follicle: erector pili muscle, oil glands and hair root nerve plexus. Erector pili muscle action produces responses to cold or anger. Sebaceous (oil) glands can be stimulated by hormones (acne during puberty).
Sweat glands have a coiled tube near or touching vasculature and an excretory tube. Sweat is a plasma filtrate , made up of small molecular weight compounds (electrolytes, sugar, water). The initial filtrate is isotonic with plasma, but Na+ and K+ are reabsorbed by the excretory tube in order to make sweat easier to evaporate.
There are two types of sweat glands: apocrine and eccrine. Apocrine glands are analogous to the scent glands of other animals, but their function in humans is not well understood. Apocrine sweat contains more lipids and proteins.
Nails are made of hard keratin.
Continue to "Wound Healing" or take a quiz: [Q1] [Q2].
Need more practice? Answer the review questions below.
1- Briefly describe the general structure of hair.
2- List the types of hair and were are they found.
3- What is the difference between age-related hair loss and male-pattern baldness?
4- What is the origin of hair color?
5- List the structures associated with hair ad their functions.
6- Describe sweat glands anatomy.
7- How is sweat formed?
8- List and describe the types of sweat glands.
9- What are nails made of?