Lecture 1 anatomy of the skin part 1

Question 1

Skin

Answer 1

The skin is the largest and most visible organ of the body.

It is 16% of body weight and covers 1.5-2 m^2 of surface area

Question 2

Why does the skin make us uniquely human?

Answer 2

Our bare, sweaty skin makes us unique

Question 3

Functions of the skin

Answer 3

Protects underlying tissues and organs against impact, abrasion, fluid loss and chemical attack

Excrete salts, water, and organic wastes by integumentary glands

Maintain normal body temperature through either insulation or evaporative cooling, as needed

Produce melanin, which protects underlying tissues from ultraviolet radiation

Produce keratin, which protects agains abrasion and serves as a water repellent

Synthesis vitamin D3, a steroid that is subsequently covered to calcitriol, a hormone important to normal calcium metabolism

Store lipids in adipocytes in the dermis and in adipose tissue in the subcutaneous layer

Detect touch, pressure, pain and temperature stimuli, and relay that information to the nervous system

Question 4

How does skin anatomy relate to its function or performance?

Answer 4

Aging
Pigmentation
Skin cancer
Tattoo

Question 5

4 types of tissue

Answer 5

Nervous, muscle, Connective and epithelial tissue

Question 6

Epithelial tissue

Answer 6

Covers exposed surfaces
Lines internal passageways and chambers
Forms secretory glands

Question 7

Connective tissue

Answer 7

Fills internal spaces
Provides structural support
Stores energy

Question 8

Muscle tissue

Answer 8

Contracts to produce movement. Includes skeletal muscle, cardiac muscle and smooth muscle

Question 9

Nervous tissue

Answer 9

Conducts electrical impulses. Carries information.

Question 10

Skin and tissue types

Answer 10

Skin is an organ made up of all 4 tissue types/the skin is a composite organ that contains all these different cell types

Question 11

3 primary layers of skin

Answer 11

Epidermis (outermost layer)
Dermis
Hypodermis

Question 12

Epidermis

Answer 12

Stratified barrier 
Mostly keratinocytes (skin cells that have heaps of the keratin protein which helps to protect the skin) 
No circulation (avascular)

Question 13

Dermis

Answer 13

Protein fibres present for strength - elastin and collagen
Vascular (nourishes the epidermis)
Not shed - if a cell dies in the dermis, it gets broken down through the vasculature just like any other cell in the internal part of our body

Question 14

Hypodermis

Answer 14

Contains adipose tissue - insulation and also important for storing energy
Subcutaneous

Question 15

Cutaneous layer

Answer 15

epidermis and dermis

Question 16

Subcutaneous layer

Answer 16

hypodermis

Question 17

Cutaneous vs subcutaneous

Answer 17

Cutaneous is anything which is related to the skin. Subcutaneous - anything that lies below the skin, and between that and the fascial layers, like Fat, Blood vessels etc.

Question 18

Papillary layer

Answer 18

Part of the dermis

Made up of little protrusions and capillaries that sit right under it that provides nourishment to the dermis and the epidermis

Projects into the epidermis

Question 19

Reticular layer

Answer 19

Part of the dermis

Made up of elastin and collagen that form a mesh for strength (mesh/mat-like structure)

Question 20

Layers of the epidermis

Answer 20

Stratum corneum(most superficial layer) 
Stratum lucidum (only found in thick skin, not found in thin skin ) 
Stratum granulosum 
Stratum spinosum
Stratum basale

Question 21

Stratum corneum (horny layer)

Answer 21

Outermost layer of the epidermis

Dead, dried-out hard cells without nuclei (provides protective mechanisms) (consists entirely of dead cells)

Horny because of the large amount of keratin (can remember because the HORN of a rhino has a lot of keratin)

Question 22

What is the layer of the epidermis that is only present in thick skin?

Answer 22

Stratum lucidum (not in thin skin)

Question 23

Stratum granulosum (granular layer)

Answer 23

Contains granules that promote dehydration of the cell, cross linking of keratin fibres - as these cells are dying and being shed and coming towards the outside they progressively dehydrate and there is cross linking of keratin fibres to try make a very strong, hard barrier to the outside

Waxy material is secreted into the intercellular spaces

Question 24

Stratum spinosum(spiny layer)

Answer 24

Intercellular bridges called desmosomes link the cells together. This creases a barrier fruition to the outside and you need these very tight junctions as an epithelial cell barrier (protective) (Characterised by desmosomes (and as the tissue sections start to dry out they start to become long and spindly hence their name))

The cells become increasingly flattened as they move upward.

Question 25

Stratum basale (basal layer)

Answer 25

Columnar (tall) regenerative cells

As the basal cell divides, a daughter cell migrates upwards to replenish the layer above. The flow of cells is from here upwards.

Question 26

Strip-taping

Answer 26

Stratum corneum (horny layer) can be completely removed and very easily too (with tape)

Question 27

The epidermis as keratinocyte conveyor belt…

Answer 27

Start off with producing cells in the stratum basal and then moving their way upwards. The skin is constantly regenerating, the skin cells turnover every 7 to 10 days.

Question 28

Infections and the skin

Answer 28

Infection cannot really bother the outer layer because it is dead therefore the dead layer is important.

Perhaps you can get an infection in one of the layers that are living underneath in the granulosum or spinous layers, because the skin cells turnover every 7 to 10 days so we would essentially grow out that infection and this therefore protects us from getting infections.

Question 29

What tissue type dominates in the epidermis?

Answer 29

Epithelial tissue

Question 30

Epithelial cell types

Answer 30

Simple epithelia (one layer) - squamous, cuboidal and columnar 
Stratified epithelia (many layers)- squamous, cuboidal and columnar

Question 31

Epidermis mainly consists of which epithelial cell type?

Answer 31

Epidermis = stratified squamous epithelium (mainly)

Question 32

Thick vs thin skin

Answer 32

Palms of hands and soles of the feet have thick skin as these are area of high abrasion, more exposure to environment

No hair on thick skin and there is also an extra epidermal layer (stratum lucidum)

Question 33

What happens as skin ages?

Answer 33

Thin epidermis
Thin dermis (sagging and wrinkling) - reduced collagen. The protein network/reticular layer starts to degrade and become thinner therefore there is less structure which means the individual is more susceptible to sagging and wrinkling
Slower skin repair
Drier epidermis (less sebum) - less oils and protective substances therefore a less effective barrier
Impaired cooling (less sweat) - this is why the older generation is more prone to be affected by overheating
Less pigmentation - pale skin and grey hair (fewer melanocytes)
Altered hair and fat distribution and fewer active hair follicles

Question 34

Smoking and skin ageing

Answer 34

There is a claim that smoking increases skin ageing

“Reactive oxygen” damages collagen and elastin - which would give the individual more wrinkles

Vasoconstriction - nicotine increases vasopressin, this decreases circulation to the outer dermis