Integumentary System (6)

Question 1

What is the skin?

Answer 1

> Largest organ of body

> Structure and function relate to its provision of the main interface between the body and the external environment

Question 2

What are the general functions of the skin?

Answer 2

1) Protection
2) First line of defence against pathogenic organisms
3) Provides a physical barrier
4) Bactericidal skin secretions provide a degree of chemical protection
5) Impervious nature (doesn’t easily let things through) and it’s role as a physical barrier protects the body from chemical agents.

Question 3

Functions of the skin- excretion composition

Answer 3

> Sodium composition may vary of we are sodium deficient
Sweat contains substances including metabolic waste products, so skin is a route of excretion for these substances
Even in cool conditions, sweat accounts for 10% of water output from the body
In hot weather, sweat secretion can raise to 4l/day, exceeding other losses such as urine

Question 4

Functions of the skin- Tissue dehydration

Answer 4

> the skin prevents tissue dehydration
The structure of the epidermis makes the skin impervious to water (doesn’t allow it through)
Prevents evaporative water loss to atmosphere
Surgery/extensive burns breach the skin and expose underlying “wet” tissues to the atmosphere, causing extensive water loss by evaporation- life threatening.

Question 5

Functions of the skin- support and shape

Answer 5

> Support of internal organs is provided by muscles of the body wall but is facilitated by the rough and durable nature of the skin
Muscles, skin and adipose tissue contribute to shape which differentiates the genders
Skin also makes clear effects of ageing on tissues
Loss of elasticity occurs as it wrinkles with age (also happened with other organs).

Question 6

Functions of the skin- regulation of body temperature

Answer 6

> Bodies gain heat from metabolism and lose heat to the environment
Maintaining optimal body temperature of essential organs is an important part of homeostasis (vasodilation and vasoconstriction)

Question 7

Functions of the skin- metabolic functions

Answer 7

Synthesis of vitamin D in dermal blood vessels

Question 8

Functions of the skin- Blood reservoir

Answer 8

Skin blood vessels store up to 5% of the body’s blood volume

Question 9

Functions of the skin- excretion

Answer 9

Limited amounts of nitrogenous wastes are eliminated from the body as sweat

Question 10

What is the epidermis?

Answer 10

> Made of squamous epithelium
Consists of multiple layers of simple flattened cells on a basement membrane of protein
The epidermal thickness determines if the skin is thick or thin
Thick skin covers areas subject to abrasion where the epidermis consists of 5 layers
Thin skin consists of 4 layers with all these being thinner
Basal layer (stratum Basale)- Sits on basement membrane which separates the epidermis from the dermis, often called germinal layer as mitosis occurs here. Daughter cells move towards the surface and form different layers

Question 11

What are the properties of the epidermis?

Answer 11

> Hard layer gives skin its protective properties to protect against physical stresses, bacteria and chemicals
Cells continuously lost in day to day activities
Most of house dust bedding is made of these cells
Areas of skin that are exposed to considerable frictional stress (e.g. soles of feet) have another layer of cells, stratum lucidum.
Cells produce eleidin which cushions and absorbs shearing stresses e.g. during walking
No blood vessels within the epidermis (avascular)
Cell needs are met by blood vessels within the dermis

Question 12

What makes up skin colour?

Answer 12

1) Melanin pigment- Yellow to reddish-brown to black pigment, responsible for dark skin colours
- Freckles and pigmented moles result from local accumulations of melanin

2) Carotene pigment- Yellow to orange pigment, most obvious in palms of hands and soles of feet
3) Haemoglobin pigment- Reddish pigment responsible for the pinkish hue of the skin
4) Cyanosis- Poorly oxygenated haemoglobin
5) Pallor- During emotional stress, blood diverted away from skin to internal organs. Low blood pressure and anaemia also causes pallor.

Question 13

What are the different types of sweat glands?

Answer 13

1) Eccrine- found in palms, soles of feet and forehead
2) Apocrine- found in auxiliary and anogenital areas
3) Ceruminous- modified apocrine glands in external ear canal that secrete cerumen
4) Mammary- specialised sweat glands that secrete milk

Question 14

What is a nail?

Answer 14

A scale like modification of the epidermis on the distal, dorsal surface of the fingers and toes

Question 15

What is hair?

Answer 15

> Strands of dead keratinised cells produced by hair follicles
Contains hard keratin which is tougher and more durable than soft keratin of the skin
Made up of the shaft projecting from the skin and the root embedded in the skin
Consists of a core called the medulla, a cortex and an outermost cuticle
Pigmented by melanocytes at the base of the hair

Question 16

What are the functions of hair?

Answer 16

> Helping to maintain warmth
Alerting the body to presence of insects on the skin
Guarding scalp against physical trauma, heat loss and sunlight
It is distributed all over body apart from palms, soles, lips, nipples and parts of external genitalia

Question 17

What are the types of hair?

Answer 17

1) Vellus- pale, fine body hair found in children, develops on most of body during childhood
2) Terminal- coarse, long hair of eyebrows, scalp, axillary and pubic regions. Caused by effect of androgens during adolescence

Question 18

What are the developmental aspects of the skin?

Answer 18

1) Lanugo- Downy coat of delicate hairs covering the foetus
2) Vernix caseosa- Substance produced by sebaceous glands that protects the skin of foetus in the amnion
3) Ageing hair
4) Grey hair- as hairs stop producing melanin, loses shine as it doesn’t reflect light, usually genetic in origin.

Question 19

What are the developmental aspects of the skin?

Answer 19

1) Lanugo- Downy coat of delicate hairs covering the foetus
2) Vernix caseosa- Substance produced by sebaceous glands that protects the skin of foetus in the amnion
3) Ageing hair
4) Grey hair- as hairs stop producing melanin, loses shine as it doesn’t reflect light, usually genetic in origin.

Question 20

What are the 2 layers of the skin?

Answer 20

1) Epidermis- Composed of squamous epithelial cells and is the outermost protective shield of the body. Not vascularised. Nutrients reach it by diffusing through the tissue fluid from the blood vessels in the dermis.
2) Dermis- A tough, leathery layer composed of mostly dense connective tissue. Vascularised.

Question 21

What are the 5 layers of the skin?

Answer 21

1) Stratum Basale (basal layer)
2) Stratum Spinosum (prickly layer)
3) Stratum Granulosm (granular layer)
4) Stratum Lucidium (clear layer)
5) Stratum Corneum (horny layer)

Question 22

What is the Stratum Basale?

Answer 22

> First layer of epidermis
Seperates the dermis from the epidermis
Often called the germinal layer because mitosis takes place here
Daughter cells move towards the surface to form the other layers

Question 23

What is the Stratum Spinosum?

Answer 23

> Second layer of epidermis (layer above stratum basale)
Several cells thick
Has many spinelike extensions which interlock and form a tough and durable structure

Question 24

What is the Stratum Granulosm?

Answer 24

> 1-5 cells layers
Cells begin to ascend and flatten and begin to produce a substance that will eventually become keratin (tough waterproofing)

Question 25

What is Stratum Lucidium?

Answer 25

> Fourth layer of epidermis

> Only found in thick skin

Question 26

What is Stratum Corneum?

Answer 26

> 20-30 cell layers thick

> These cells are shed regularly