Anatomy and Cell Biology 3309 Lecture Notes - Lecture 14: Apocrine Sweat Gland, Arrector Pili Muscle, Eccrine Sweat Gland
22 May 2018
School
Department
Professor
Histology 3309
Skin Derivatives: Hair, Nails, Sweat and Sebaceous Glands
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
Skin Derivatives
- Keratin based (hard keratin due to crosslinkages of sulphur groups):
o Hair follicle
o Nails
- Glandular
o Sebaceous glands
o Eccrine sweat glands
o Apocrine sweat glands
Today’s Overview Slide
- What type of skin are we looking at? Thin skin (bc there is a hair follicle there)
- You can see an eccrine sweat gland (tubular structure – does loops up through the dermis on its
way to the epidermis)
- Apocrine gland is less coiled than the eccrine gland
- The apocrine gland secretions are continuous with the hair follicle – its secretions are released
into where that hair is protruding
- Note: when hair comes out of your head, it is dead but we do have some stem cells in some parts
of the hair that contribute to the growth of the hair
- We also have a sebaceous gland – also secretes its contents along
the hair shaft
- We also have an arrector pili muscle
o Part of our evolution – defence mechanism in animals
(makes them look bigger) and emotional response in
humans
o Pulls the hair shaft up (goosebumps)
- Hair shaft is what the hair is refered to once it comes out of the
epidermis
- Terminal hair (pubic, head, axillary); vellous is fine hair
- A hair is strand made of keratinized cells. Root = part of hair in the
skin; shaft = part of hair that projects from the skin
- Let’s talk about the root part...
- Hair follicle is a tubular invagination of the epidermis from which
the hairs grow
- Arrector pilli muscle assoc with each hair follicle
find more resources at oneclass.com
find more resources at oneclass.com
Hair Follicles and Hair
- Hair follicle (HF) is responsible for growth and production of hair
- Infundibulum:
o from surface opening to opening of sebaceous gland (SG)
- Isthmus:
o from indfundibulum to arrector pili muscle insertion
- our hair shaft is made of hard keratin and there is 3 parts to it:
o cuticle – outermost part
o cortex
o medulla – inntermost part
▪ you might not find a medulla in fine velous hair (hair on your cheeks, innerpart
of forearms, back of hand etc)
▪ the difference with these hairs is that they don’t have a medulla
- there is a bulge region
o source of epidermal stem cells
o during wound healing, stem cells from here can contribute to forming new skin
- hair bulb
o made of dermal papilla and matrix cells
o there is some innervation and blood supply here (if you pull hair out of your head, it will
hurt bc there is innervation there but if you cut your hair, it wont hurt)
o dermal papilla and matrix cells give rise to the internal rooth sheath (IRS)
o IRS does not contribute to the hair itself (its not part of the hair shaft)
o You also have an outer root sheath (ORS)
▪ Caused by a downgrowth of epithelium during development
o Note: for crime scenes, they must have some of the cells from the actual hair bulb
- In order to understand hwo hair is made, we have to look at the deepest part of the hair follicle,
which forms the bulb
- Matrix:
o Growth zone
- Melanocytes:
o Give pigment to the hair shaft as it is produced
- Papilla
o Protrusion of the dermis into the bulb
o Carries some of the blood supply (which is necessary if cells there are undergoing
proliferation bc they need O2, nutrients etc)
- Overlying the dermal papilla is a layer of keratinocytes that for m the hair
o External root sheath
o Internal root sheath
find more resources at oneclass.com
find more resources at oneclass.com
- The hair follicle is responsible for the growth and production of the hair
- From inner to outer is the hair shaft, the internal root sheath and the external root sheath
- The hair matrix cells are our stem cells
o they produce the hair
o they contribute to the internal root sheath
- the external root sheath is a down growth of the epithelium
- inner to outer, we have the medulla, hair cortex, hair cuticle (this is the layers of the external
root sheath)
- then from layers 4-6, it’s the internal root sheath – layers of cells derived from the matrix cells
o internal rooth sheath cuticle, huxleys layers, henles layer
Hair – shaft and follicle in more detail
- the medulla, cortex and cuticle cells are the layers that are actually forming your hair (the part
that is actually coming out of your head) →the other parts don’t come out of your head as they
are apart of the internal or external root sheath
- there is also a connective tissue sheath that is around that hair
- A hair is made of three concentric layers of keratinized cells. The keratin is harder tough than
keratin of the epidermis.
- Central cylinder is medulla. BTW, Vellus hair may not have medulla.
- middle layer is cortex
- outermost thin layer is cuticle
- Follicle is made of root sheath.
- - Epithelial root sheath = internal root sheath (stops at level of sebaceous gland) + external root
sheath (Ext RS is continuous w/ epithelium)
- - The basement membrane for the extranal rooth sheath is called the glassy membrane.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Skin derivatives: hair, nails, sweat and sebaceous glands. Keratin based (hard keratin due to crosslinkages of sulphur groups): hair follicle, nails. Glandular: sebaceous glands, eccrine sweat glands, apocrine sweat glands. Today"s overview slide way to the epidermis) into where that hair is protruding. Apocrine gland is less coiled than the eccrine gland. Thin skin (bc there is a hair follicle there) You can see an eccrine sweat gland (tubular structure does loops up through the dermis on its. The apocrine gland secretions are continuous with the hair follicle its secretions are released. We also have a sebaceous gland also secretes its contents along: part of our evolution defence mechanism in animals (makes them look bigger) and emotional response in humans. Note: when hair comes out of your head, it is dead but we do have some stem cells in some parts of the hair that contribute to the growth of the hair the hair shaft.
