Mod2-Obj6: The skin

Question 1

skin contains the 4 primary tissues

Answer 1

1.) Stratified squamous 
Epithelial tissue in the epidermis
2.) Connective tissue
In the dermis
3.) Smooth muscle tissue
In the arterioles attached to hairs
4.) Nervous tissue
In sensory nerves

Question 2

The skin

Answer 2

Largest and heaviest organ
-Covers the entire body and weighs 4-5kg
-Part of the integumentary system (skin, glands, hair, nails)
Integument=covering

Question 3

Layers of the skin

Answer 3

Consists of 2 layers
1.) Epidermis
Outer epithelial layer
2.) Dermis
Supporting layer of dense connective tissue

Question 4

Hypodermis

Answer 4

Loose connective tissue and fat

• Anchors skin to the body
• Not part of the skin

Question 5

The epidermis: Avascular

Answer 5

Like other epithelium

-Oxygen and nutrients obtained from dermis

Question 6

The epidermis: Dynamic steady state

Answer 6

Cells constantly die and renew

-New cells originate from stem cells

Question 7

The epidermis: Constant renewal

Answer 7

Epidermis replaced every 25-45 days

Question 8

The epidermis

Answer 8

Cells move from deepest layer to more superficial layer

• Flatten
• Produce large amounts of keratin
• Continually replenished

Question 9

The 5 epidermal layers (strata)

Answer 9

1. ) Stratum basale (basal/deepest layer)
2. ) Stratum spinosum
3. ) Stratum granulosum (cells begin to die)
4. ) Stratum lucidum
5. ) Stratum corneum (most superficial layer)-cells are dead, produce large amounts of keratin providing waterproofing for the surface of the body

Question 10

The epidermis: Stratum corneum (top)

Answer 10

20-30 cell layers

-Dead keratinised flattened cells

Question 11

The epidermis: Stratum basale (bottom)

Answer 11

Stem cells

-Old cells pushed to surface

Question 12

5 cells of the epidermis

Answer 12

1.) Karatinocytes 
Produces keratin 
2.) Melanocytes
Produces melanin
3.) Merkel cells
Touch receptors (tactile)
4.) Langerhanan's cells
Immune system (macrophages), bone marrow

Question 13

The dermis

Answer 13

-Bulk of the skin
Connective tissue
-Fibroblasts and macrophages 
-Collagen and elastin fibres
-Strength and flexibility

Question 14

Dermis contains

Answer 14

• Blood vessels
• Nerves and sensory receptors
• Glands
• Hair follicles

Question 15

Blood supply to the skin

Answer 15

Dense capillary network in hypodermis
-Capillary loops project up through dermis
Blood flow through loops regulates by capillary sphincters
-temperature control (homeostasis)-vasoconstriction/vasodilation

Question 16

Nerve supply to the skin: Network of nerve fibres

Answer 16

Dense network of fibres
Control:
-Blood flow (via sphincter)
-Glandular secretion i.e.) sweat

Question 17

Nerve supply to the skin: Sensory information

Answer 17

Collect sensory information

• Pain
• Temperature
• Touch and pressure

Question 18

6 Functions of the skin

Answer 18

1. ) Protection (chemical, physical, biological)
2. ) Sensation
3. ) Metabolic function
4. ) Blood reservoir
5. ) Excretion
6. ) Temperature regulation

Question 19

Function of the skin: Protection

Answer 19

Offered by chemical, physical and biological barriers

Question 20

Protection: Chemical barriers

Answer 20

• Low pH secretions (acid mantle) prevent bacterial growth
• Defensins secreted by skin to kill bacteria/fungi
• Melanin protects DNA in underlying cells from UV damage

Question 21

Protection: Physical/mechanical barriers

Answer 21

• Keratin and oily secretions block most water and water soluble substances
• Some penetration of skin by lipid-soluble substances, some drugs (topical)

Question 22

Protection: Biological barriers

Answer 22

Macrophages dispose of viruses and bacteria that penetrate the epidermis

Question 23

Functions: Sensation

Answer 23

Cutaneous sensation

3 receptor types (providing information about external environment)

Question 24

Function: Sensation; Pain receptors

Answer 24

Noiceceptors

Question 25

Function: Sensation; Temperature receptors

Answer 25

Thermoreceptors

Question 26

Function: Sensation; Touch, pressure and vibration receptors

Answer 26

Mechanoreceptors

Question 27

Functions: Metabolism

Answer 27

Synthesis of vitamin a precursor

Question 28

Functions: Blood reservoir

Answer 28

Can hold 5% of blood volume

Question 29

Functions: Excretion

Answer 29

Nitrogenous wastes and salts excreted in sweat

Question 30

Function: Temperature regulation

Answer 30

At elevated temperature dermal blood vessels dilate and sweat gland activity increases -Cools the body

Question 31

Function: Temperature regulation (heat input and output balanced)

Answer 31

- Monitored by thermoreceptors - Information sent to thermoregulatory centre (hypothalamus)- set point - Coordinated response via circulatory system (vasoconstriction/vasodilation) and sweat glands - Homeostasis

Question 32

Skin colour: Melanin

Answer 32

Produced by melanocytes - Melanin migrates to keratinocytes - Forms 'pigment shields' for DNA

Question 33

Skin colour: Freckles and pigment moles

Answer 33

Local accumulation of melanin

Question 34

Skin colour: Melanocytes stimulated when exposed to sunlight

Answer 34

Darker skin produces more melanin

Question 35

Diseases and altered colour: Cyanosis (blue)

Answer 35

Lack of oxyhaemoglobin

Question 36

Diseases and altered colour: Erythema (redness)

Answer 36

Inflammation, allergy, fever

Question 37

Diseases and altered colour: Pallor (white)

Answer 37

Anaemia, low BP, stress

Question 38

Diseases and altered colour: Jaundice (yellow)

Answer 38

Liver disorder

Question 39

Diseases and altered colour: Bronzing (metallic bronze)

Answer 39

Adrenal cortex problem or pituitary gland tumor

Question 40

Diseases and altered colour: Bruises (black/blue)

Answer 40

Blood clots

Question 41

Development and ageing

Answer 41

The effects of abrasion, sun, chemicals - Skin thins-Cell number - Wrinkles form-Collagen&elastin - Dry and itchy-Oil and sweat glands - Increased chance of skin cancer-Melanocyte number - Age spots, hair loss, grey hair, colder skin, thicker nails