Skin Appendages

• Eccrine glands are those in which secretory product is expelled by exocytosis. Eg sweat glands involved in thermoregulation and receiving cholinergic sympathetic innervation.
• Apocrine glands are those in which the secretory product accumulates in the apical cytoplasm and is expelled out by pinching of the apical plasma membrane. Eg mammary gland and apocrine type of sweat glands that are active after puberty and are found in the skin of axilla and around genital organs.

B i.e. Sebaceous glands

C i.e. Sebaceous gland 

The lumen of sebaceous gland is filled with secretory cells undergoing cytolysis (holocrine secretion)Q, a process where by the cells degenerate to become the oily secretory product of the gland called sebum. The duct is lined with stratified squamous epitheliumQ that has continuity with the external root sheath of hair follicle.

B i.e. Ectopic Sebaceous gland

B i.e. Modified sebaceous gland

Ans is A i.e. Modified sweat glands, C i.e. Present in axilla and groin

• Sweat glands are of two types:

1)Eccrine (Merocrine) or typical sweat glands.

2)Apocrine or atypical sweat glands.

• Eccrine or Typical sweat glands

–   Distributed all over the body ; most numerous in the palms and soles, the forehead and scalp and the axilla.

–  Have a role in control of body temperature.

– Innervated by cholinergic nerves.

• Apocrine or Atypical sweat glands

– Apocrine glands are particularly large glands of the dermis or hypodermis, classed as a type of sweat gland. In the adult, they are present in the axillae, perianal region, areolae, periumbilical skin, prepuce, scrotum, mons pubis and labia minora.

– The excretory ducts open into the hair follicle (instead of on the skin surface as in the eccrine sweat gland)

–  Apocrine sweat glands are functional after puberty and are supplied by adrenergic nerves.

– The secretions of apocrine sweat glands are viscous and contain proteins. They are odourless but after bacteria decomposition they give off body odours that vary from person to person.

Hidradenitis suppurativa is a chronic inflammatory process of the apocrine glands bearing skin characterized by abscesses and sinus formation.

Ans. B i.e. 0.4 mm/ day

Ans. C: CSF

Ans. B i.e. Sebaceous glands

Ans. 4-10 times broader than the medulla

Ans. b. Arrector pill

Arrector pill is a smooth muscle in the dermis, derived from lateral plate mesoderm.”— Langmans Medical embryology 12/e p341

“The arrector pili is a mesodermally derived smooth muscle that lifts the hair to a nearly vertical position in a cold environment.”- Human embryology and developmental biology by Carlson-5/chapter-9/integumentary-system

Ans. is ‘c’ i.e., 100 days

• The most important feature of hair follicle is that their activity is cyclic. Hair grows at 0.4 mm per day and as it reaches a definitive length, it is shed to be replaced by a new hair. Hair undergoes through 3 different phases of hair cycle :‑

1) Anagen phase (Phase of activity and growth)

• This is the phase in which growth of hair takes place -4 Cells in the root of hair are dividing rapidly. Melanogenesis also occurs during anagen phase. This phase lasts for 3 years (2-6 years). Most of the hair (75-80%) are in anagen phase at a given time.

2) Catagen phase (Transition phase)

• It is the transition phase between anagen and telogen. 3% of hair are in this phase. During this phase growth stops and outer root sheat shrinks and attaches to root of hair known as club hair. This phase lasts for 2-3 weeks.

3) Telogen phase (Resting or degenerative phase)

• This phase is the resting phase and lasts for 100 days (3 months). About 25-100 telogen hair are shed normally each day. 10-15% of hair are in this phase. After telogen phase the cycle is complete and the new hair, which starts growing in same follicle, pushes this old hair (who has completed the hair cycle) —> Old hair is lost and new hair starts growing.
• This hair cycle of one hair is independent of the cycle of neighboring hair, i.e., the neighboring hair follicles are not synchronized in growth, this is called Mosaic. The proportion of hair in each phase can be estimated by looking at the plucked hair called as trichogram.

Ans. is ‘a’ i.e., Modified sweat gland