Anatomy and Cell Biology 3309 Lecture 48: Nails, Hair, Sweat Glands
2 May 2018
School
Department
Professor
Hair, Nails, Sebaceous, Glands, Sweat Glands
January 11 2018
Learning Objectives
1. Describe the structure of the hair follicle and explain the role of matrix cells in the production of hair
2. List the structural components of nails and their functions
3. Explain the structure of sebaceous glands and how sebum is produced
4. Compare and contrast eccrine and apocrine sweat glands in terms of structure and function
- Eccrine – exercise, thermoregulation
- Apocrine – makes us similar to skunks + dogs
Case Study
- Took off that part of the skin with the moles & was given a skin graft
o Want to get rid as much of the melanoma as possible
- If cancer is localized – you can remove it
o It has not metastasized to the lymph node – clear sentinel biopsy
- Take off lesion skin with the melanoma on it & replaced with skin graft from the thigh
- What parts of the skin should the surgeon graft?
o Want the hair to be there
o Need:
▪ Stratum basale
▪ Little bit of the dermis
▪ Depending on where it was taken on the body, you may or may not have hair
there
- Note: be careful with the skin graft. With wound healing, the skin is more susceptible to injury
Skin Derivatives
- Skin appendages are derived from the downgrowths of epidermal epithelium
- Keratin Based
o Hair follicle and hair
▪ Involved in heat regulation
o Nails
▪ Protection
o Note: these are hard keratin
▪ It is due to a lot of cross linkages of sulfur groups
- Glands
o Sebaceous gland
▪ Secrete sebum
▪ Lubrication, antimicrobial
o Eccrine sweat glands
▪ Thermoregulaton
o Apocrine sweat gland
▪ Pheromone secretion
o Note: both eccrine and apocrine result in the expression of different types of sweat
find more resources at oneclass.com
find more resources at oneclass.com
Today’s Overview Slide
- If there is a hair follicle = THIN SKIN
o We do not grow hair on thick skin!!
- Eccrine sweat gland
o Tubular structure
o Simple loops on its way up to through dermis to the surface of the epidermis
o More coiled that apocrine gland
- Apocrine sweat gland
o Secretions are continuous with the hair follicle
o Secretion gets released to where the hair is protruding from the skin
- Hair, once it comes out it is dead
o BUT there are parts of the hair where there are stem cells contributing to the growth of the
hair (similar to what you see in the skin)
- Sebaceous gland
o Secrete its contents along the hair shaft
- Arrector pili muscle
o Part of our evolution
o Goosebumps & hair stands up activating these muscles
▪ In mammals such as cats + dogs, the muscles pull the hair shaft up, hair on end
• Defense mechanism for mammals – look bigger + scare off something
• Emotional response for humans
o Involved under ANS control
- It is called the hair shaft once it comes out of the epidermis
find more resources at oneclass.com
find more resources at oneclass.com
Hair Follicles and Hair
- Hair is composed of keratinized cells: develop from hair follicles
- All thin skin (some exceptions) has hair
- Hair development is heavily influenced by hormones:
o Facial + pubic hair production occurs during puberty
o Male pattern baldness changes in sex hormone levels with age
- Hair color comes from melanin
- Hair follicle (HF) is responsible for the growth of the hair and production of hair
o Fairly uniform diameter EXCEPT at the base where it is expanded to form the hair bulb
- Two parts of the hair follicle
o Infundibulum
▪ From the opening of the surface to the opening of the sebaceous gland
o Isthmus
▪ From the infundibulum to the arrector pili muscle insertion
• Note: if the arrector pili muscle is contracted, it will make the hair stand on
end
- Hair shaft
o Made of hard keratin
o 3 parts
▪ Cuticle: Outer most part
▪ Cortex
▪ Medulla
• Note: NO medulla in fine vellus hair
• We have terminal hair (hair on head) and fine vellus hair (hair on cheeks
for females, inner part of forearm, etc. hard to see)
- Hair bulge:
o Source of epidermal stem cells
o During would healing, the stem cells from the bulge region contribute to form new skin
(migrate and proliferate)
- Hair bulb = dermal papilla + matrix cells
o Dermal papilla – vascularized tuft of loose connective tissue
o Matrix cells - stem cells that divide and account for the growth of the hair keratinocytes
o Dermal papilla and matrix cells give rise to internal root sheath and hair shaft itself
▪ Internal root sheath is NOT contributing to the hair itself (NOT part of the hair shaft)
o There is innervation
▪ If you pull a hair out of head, it hurts because of the innervation – but if you were to
cut your hair, it wouldn’t
o Blood supply here
- Outer root sheath/external root sheath
o Caused by the down growth of epithelium during development
o Surrounded by basement membrane called the glassy membrane
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Apocrine makes us similar to skunks + dogs. If cancer is localized you can remove it. Took off that part of the skin with the moles & was given a skin graft: want to get rid as much of the melanoma as possible. It has not metastasized to the lymph node clear sentinel biopsy. Note: be careful with the skin graft. With wound healing, the skin is more susceptible to injury. Skin appendages are derived from the downgrowths of epidermal epithelium. Keratin based: hair follicle and hair, nails. Involved in heat regulation: protection, note: these are hard keratin. It is due to a lot of cross linkages of sulfur groups. Secrete sebum: lubrication, antimicrobial, eccrine sweat glands, thermoregulaton, apocrine sweat gland, pheromone secretion, note: both eccrine and apocrine result in the expression of different types of sweat. If there is a hair follicle = thin skin: we do not grow hair on thick skin!
