Lecture 4 - The Integument: Structure and Function

Question 1

Integument

Answer 1

The largest and most visible organ in the human body. It consists of the cutaneous membrane + accessory structures

Question 2

4 major functions of the integument

Answer 2

1. Provides a barrier against the external environment - immune and osmotic homeostasis
2. Vitamin D and Ca2+ homeostasis
3. Thermal homeostasis
4. Sense organ

Question 3

True or False: the hypodermis is a part of the integument

Answer 3

False - it is not integumentary

Question 4

Thin skin vs. thick skin

Answer 4

Thin skin - hairless. Found on palmar and plantar surfaces

Thick skin - hairy. Found everywhere else

Question 5

Name the 6 layers of stratified squamous epithelium of the epidermis from the most superficial to the deepest layer

Answer 5

Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum basale

“Come Lets Grab Some Beers”

Question 6

Describe the process of proliferation/renewal of epidermal cells

Answer 6

Epidermal cells are continuously generated:

In the deepest layers (stratum basale)

Differentiated in the middle layers (basal cells differentiate into keratinocytes in the stratum spinosum)

Shed from superficial layers

Question 7

What is insensible perspiration and how does the epidermis limit insensible perspiration?

Answer 7

Insensible perspiration is water loss through the cutaneous membrane, not through the sweat glands

The epidermis is keratinized, meaning its cells are filled with keratin (which is a tough, cross-linked, water-resistant protein) and limits insensible perspiration

Question 8

Melanin function

Answer 8

It can absorb UV photons and prevent DNA damage in cells by releasing the energy safely

Question 9

Melanocytes

Answer 9

Located in the stratum basale, they produce melanin pigments and transfer them to keratinocytes

Question 10

Melansomes

Answer 10

Organelles located inside melanocytes that synthesize and store melanin pigments

Question 11

Explain how melanocytes, melanosomes, and melanin contribute to different skin colours

Answer 11

Darker skin is due to melanocytes bring more active, transferring more melanosomes more frequently. Furthermore, there are different versions of melanin, which contribute to different hues of skin colour

Question 12

Dermis

Answer 12

Contains connective tissue and accessory structures that support the epidermis or allow for secondary skin functions

Question 13

Name general examples located inside the dermis layer

Answer 13

Stratum papillare (loose)
Stratum reticulare (dense, irregular, elastic)
Accessory structures (ex. sensory neurons, hairs and glands)
Extensive vasculature

Question 14

Are neurons present in the dermis?

Answer 14

Yes - the dermis contains somatosensory (touch and nociceptive (pain) neurons. Everyone’s skin has the ~same number of sensory neurons per unit area

Question 15

Hair and nails function

Answer 15

They are highly keratinized accessory structures and help serve to protect the integumentary system. The hair shaft and nail bodies are made up of dead cells

Question 16

Glands function

Answer 16

Epithelial structures in the integument that serves to protect and/or maintain homeostasis

Question 17

Describe the difference in healing process between the epidermis and dermis

Answer 17

The first stage is the same for both - an inflammatory response increases blood flow and there is an attraction of immune pathocytic cells at the site. Then:

Epidermis - undergoes proliferation from basal cells and granulation tissue forms. A scab formed at the surface

Dermis - undegoes recruitment, proliferation, and differentiation. Very high proliferation and secretion from fibroblasts results in keloid scar formation

Question 18

Significance of skin in thermal homeostasis

Answer 18

It plays an important role in being a sensor and effector in thermal homeostasis through evaporative cooling and radiant cooling (vasodilation allows heat loss across the epidermis)

The redness on people’s face after exercising or consuming alcohol is due to increased blood flow to superficial dermal layers - light skin isn’t thinner, just more transparent

Question 19

Significance of the epidermis in calcium homeostasis

Answer 19

It synthesizes Vitamin D, which is needed to synthesize calcitriol (a hormone), thereby contributing to calcium homeostasis

Question 20

Trade-off between melanin and vitamin D synthesis

Answer 20

Less vitamin D results in less cell damage because the upper layers of the epithelium absorb more UV light, meaning less reach the basal layers

More vitamin D results in more cell damage because the upper layers let more UV light through to basal layer

Question 21

Intensity of UV radiation and latitude

Answer 21

At high altitudes (ex. Canada), there is less UV that can be absorbed. So, sunscreen is more efficient and dietary vitamin D is more necessary. The less UV in the environment, the less gets through the melanin to reach basal layers

Question 22

How are changes in the skin and other integumentary structures seen?

Answer 22

Most visible signs is ageing. These changes compromise the critical physiological functions of skin