Anatomy and Cell Biology 3309 Lecture Notes - Lecture 1: Stratified Squamous Epithelium, Lamellar Corpuscle, Merkel Cell
15 May 2018
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Lecture 1 – Histology of the Skin
- Largest organ in the body and very complex
- Below the epidermis is the dermis
- There are many structures contained within the dermis:
o Sebaceous glands (oil glands)
o Hair follicles
o Sensory organs: pacinian corpuscles (vibration stimuli), merkel cells (fine touch)
Layers of skin
Epidermis
- Basophilic staining layer
- Skin is continuously sloughed off (shed/removed) and we lose a bit of our skin everyday
- Stratified squamous epithelium
- From ectoderm
- Continuously shed
Dermis
- Beneath the epidermis
- Loose and dense irregular CT (lots of collagen)
- From mesoderm
- Gives mechanical support, strength and thickness
- Dermis beneath the epidermis helps to maintain the overall structure of the skin (epidermis
is very thin and don’t want it sliding around)
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Hypodermis
- Variable amounts of adipose tissue arranged into lobules
- Deeper than dermis
- Adipocytes are arranged into lobules
- Amount of adipocytes that you have depends on the individual (age, amount of fat in their
body)
- As individuals age, they lose some of the adipocytes in the hypodermis = they get colder
because they cannot thermoregulate as much
o In young people, skin springs back pretty quick and it is elastic
o But in old people, skin does not spring back as much (lose elasticity)
- Hypodermic needles: needles are injected into the hypodermis
Functions of the skin
- Barrier - protects against physical, chemical, and external environmental biologicals
o In individuals with very severe burns that compromise a large amount of their skin
are very prone to infection
o Burns can be deadly because the skin does a very good job as acting as a barrier
- Immunologic - Langerhans cells
o Has its own antigen-presenting cells
- Homeostasis - regulates body temperature and water loss (shivering, sweating, hair)
o Individuals with anorexia have more hair on their body because their body is trying
to compensate and maintain homeostasis because they lost some of hypodermis
- Sensory information – acuity varies, about the external environment
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o Sensory homunculus: how our skin and body are mapped onto our brain (lips, finger
tips – areas have a denser concentration of different sensory organs)
- Endocrine functions - produces some hormones and cytokines, vitamins
o Involved in vitamin production (vit. D)
- Exocrine function - sweat, oil, apocrine glands
Thick skin
- When talking about skin thickness histologically, we are talking about the thickness of the
epidermis (NOT the overall thickness of the skin)
- Varies from 1-5mm thick
- When comparing and contrasting thick vs thin skin we are talking about the layers of the
epidermis
- If considered all of the layers (epidermis, dermis, hypodermis) and looked at all of those
layers, the thickest skin would be on the upper back
o There is a large layer of dermis there but poor sensory acuity
Thin vs. thick skin
- LEFT: thin skin
o Looks like a thick dermis but we are considering the epidermis
- RIGHT: thick skin
o Places where you can get calluses (feet, hands)
o Thicker layer of the epidermis and primarily the statrum corneum
o Stratum corneum is the part that gets sloughed off
- If see a hair follicle in a histological section, know immediately that you are looking at thin
skin (thick skin does not have hair follicles associated with it)
In which layer of the skin would you expect to find adipocytes?
a) Epidermis
b) Rete ridges
c) Dermis
d) Hypodermis
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Largest organ in the body and very complex. There are many structures contained within the dermis: sebaceous glands (oil glands, hair follicles, sensory organs: pacinian corpuscles (vibration stimuli), merkel cells (fine touch) Skin is continuously sloughed off (shed/removed) and we lose a bit of our skin everyday. Loose and dense irregular ct (lots of collagen) Dermis beneath the epidermis helps to maintain the overall structure of the skin (epidermis is very thin and don"t want it sliding around) Variable amounts of adipose tissue arranged into lobules. Amount of adipocytes that you have depends on the individual (age, amount of fat in their body) As individuals age, they lose some of the adipocytes in the hypodermis = they get colder because they cannot thermoregulate as much. In young people, skin springs back pretty quick and it is elastic: but in old people, skin does not spring back as much (lose elasticity) Hypodermic needles: needles are injected into the hypodermis.
