The integumentary system

Question 1

What are the 7 functions of the skin?

Answer 1

Protection
Regulation of body temperature
Sensation
Immune defence
Excretion
Vitamin D synthesis
Water regulation
Endocrine function

Question 2

Describe the skins role in protection

Answer 2

It acts as a physical barrier, protecting the body from physical, chemical, and biological hazards such as UV radiation, pathogens, and toxins.

Question 3

Describe the skins role in body temperature regulation

Answer 3

The skin helps regulate body temperature through processes like sweating (evaporative cooling) and vasoconstriction/dilation of blood vessels (heat conservation or dissipation).

Question 4

Describe the skins role in sensation

Answer 4

The skin contains numerous sensory receptors that detect touch, pressure, pain, and temperature, allowing us to perceive and respond to stimuli from the environment.

Question 5

Describe the skins role in immune defence

Answer 5

Specialized immune cells in the skin, such as Langerhans cells and dendritic cells, help protect against pathogens and foreign substances by initiating immune responses.

Question 6

Describe the skins role in sensation

Question 7

Describe the skins role in excretion

Answer 7

Sweat glands in the skin excrete waste products, such as urea and salts, helping to regulate electrolyte balance and eliminate toxins from the body.

Question 8

Describe the skins role in vitamin d synthesis

Answer 8

When exposed to sunlight, the skin produces vitamin D, which is essential for calcium absorption and bone health.

Question 9

Describe the skins role in water regulation

Answer 9

The skin helps prevent excessive loss of water from the body through its barrier function, helping to maintain hydration and prevent dehydration.

Question 10

Describe the skins role in Endocrine function

Answer 10

The skin produces and releases various hormones and signaling molecules involved in local and systemic physiological processes. Eg. Melatonin, which is involved in regulating circadian rhythms and has antioxidant properties

Question 11

What is the dermis

Answer 11

It is a layer of the skin. It lies beneath the epidermis and is composed of connective tissue. It’s divided into 2 layers: the papillary dermis and reticular demis.

Question 12

What is the dermis composed of?

Answer 12

Blood vessels
Lymphatic vessels
Nerves
Sweat glands
Sebaceous glands
Hair follicles
Immune cells - macrophages, mast cells, fibroblasts

Question 13

What is the function of fibroblasts and where are they found?

Answer 13

In the dermis
They produce collagen and elastin fibers which contribute to the structural integrity and flexibility of the skin

Question 14

What is the function of the papillary dermis and where is it located

Answer 14

Its located just beneath the epidermis and contains finger-like projections called dermal papillae, which interlock with the epidermis and help anchor the two layers together

Question 15

What is the function and location of the reticular dermis

Answer 15

It’s the deeper thicker layer of the dermis, consisting of dense irregular connective tissue that provides strength, support, and elasticity to the skin

Question 16

What is the epidermis

Answer 16

It is the outermost layer of the skin

Question 17

What is the epidermis composed of

Answer 17

Stratified squamous epithelial tissue
It’s made up of several layers
It lacks blood vessels and relies on diffusion from the underlying dermis for nourishment

Question 18

What are the layers found in the epidermis

Answer 18

Stratum basale (or basal layer) - deepest layer
Stratum spinosum
Stratum granulosum
Stratum corneum - outermost layer

Question 19

What is the stratum basale composed of?

Answer 19

Actively dividing cells responsible for replenishing outer layers of the epidermis

Question 20

What is the stratum corneum composed of and where can it be found?

Answer 20

The outermost layer of the epidermis, and is composed of dead keratinocytes (keratinized cells) that provide protection against physical and environmental damage

Question 21

Whats the structure and function of hair?

Answer 21

Structure: Composed of a protein called keratin, arranged in three layers: the medulla (innermost layer), the cortex (middle layer), and the cuticle (outermost layer).

Function:
Protection for the scalp from UV radiation, abrasions, and minor physical trauma.
Insulation - regulates body temperature by trapping heat close to the skin when it’s cold, providing insulation
Sensation - Hair follicles are surrounded by sensory nerves, allowing hair to detect touch, movement, and changes in the environment.
Excretion - Sebaceous glands attached to hair follicles secrete sebum, an oily substance that moisturizes the hair and skin, as well as inhibiting bacterial growth.

Question 22

Whats the structure of a nail?

Answer 22

A hard, keratinous plate that grows from the nail matrix, located beneath the skin at the base of the nail. Consists of several parts:
the nail plate (visible portion)
the nail bed (the skin beneath the nail plate)
the nail matrix (the tissue at the base of the nail that produces new nail cells)
the cuticle (the thin layer of skin at the base of the nail plate)
the lunula (the white, crescent-shaped area at the base of the nail).

Question 23

Whats the function of a nail?

Answer 23

Protecting the fingertips and toes from injuries, and trauma.
Gripping and Manipulation
Sensory Function: Nails contain numerous nerve endings that contribute to tactile sensation
Structural support to the soft tissues of the fingertip, helping maintain its shape and integrity.

Question 24

Describe the process of wound healing

Answer 24

Inflammation – where the body generates a mass of chemical agents to promote cell activity

Granulation – where the body promotes the formation of new cells

Regeneration – permanent repair is complete

Remodelling – the impact of scarring is diminished

Question 25

What are the chemical barriers of the skin in relation to protection?

Answer 25

Skin secretions and melanin:
- Acid Mantle (lactic acid in sweat): retards multiplication of bacteria
- Natural antibiotic: human defensin
- UV shield: melanin and hair covering
- Water barrier: glycolipids of the epidermis

Question 26

What are the physical/mechanical barriers of the skin in relation to protection?

Answer 26

Keratinisation: provides a hard impenetrable barrier (tight junctions and desmosomes act as physical barriers)

Question 27

What are the biological barriers of the skin in relation to protection?

Answer 27

Langerhans cells (from bone marrow) when presented with antigens produce immune response. Macrophages (from blood) engulf debris and bacteria

Question 28

Explain how temperature regulation is maintained through homeostasis using the skin

Answer 28

When the external temperature is lower than the skin heat will be lost by convection and radiation. Below 31-32oC sweat glands produce very little sweat.

When body temperature rises dermal blood vessels dilate and sweat glands are stimulated to secrete more sweat (upto 12 litres/day), evaporation of the sweat from the skin dissipates body heat.

When the body temperature cools dermal blood vessels constrict and this slows heat loss. In addition the erector pili muscles contract and raise the hairs, trapping a layer of air next to the skin as an insulator.

Question 29

What are the two types of sensory cutaneous receptors and what do they respond to?

Answer 29

Meisseners corpuscles in the dermal papillae respond to gentle touch

Pacinian corpuscles (in the deeper dermal layer and hypodermis) respond to deep pressure

Question 30

What are the 3 metabolic functions of the skin?

Answer 30

Calcium metabolism, detoxifaction of carcinogens and conversion of steroids

Question 31

Explain calcium metabolisation & the link with vitamin D

Answer 31

Sunlight (UV) converts a precursor of vitamin D (7-dehydrocholestrerol) into another precursor of vitamin D (cholecalciferol) which is released into blood and is converted in the liver/kidneys to active vitamin D. Without vitamin D calcium cannot be absorbed from the digestive tract.

In addition vitamin D promotes calcium retention in bone and reduces loss from the kidneys

Question 32

Explain how the skin carries out detoxification of carcinogens

Answer 32

Keratinocyte enzymes can metabolise and render harmless many cancer causing chemicals

Question 33

Explain how the skin carries out conversion of steroids

Answer 33

Keratinocytes can convert cortizone applied topically into hydrocortisone which is an anti-inflammatory

Question 34

Describe the process and steps of inflammation in wound healing

Answer 34

Histamine, cytokine and other inflammatory chemicals released from damaged mast cells

Leads to dilation of capillaries which become permeable

White blood cells (neutrophils), plasma rich in clotting proteins and antibodies leak from blood vessels

Clotting proteins form a clot which plugs wound

Outer part of clot dries and forms a scab

Debris and damaged tissue phagocytised and carried away in lymph

Question 35

Describe the process and steps of granulation in wound healing

Answer 35

Granulation tissue is a delicate pink tissue and contains thin permeable capillaries which bud from intact capillaries nearby and give the wound a granular appearance

Wound contraction occurs as a result of the contraction of fibroblasts

Macrophages clear debris. Fibroblasts make new collagen fibres to bridge the gap

The ‘patch’ which forms releases bacteria inhibiting substances

Question 36

Describe the process and steps of regeneration in wound healing

Answer 36

Epithelium begins to regenerate.
Epithelial cells migrate across granulation tissue just beneath scab (which then detaches)

Question 37

Describe the process and steps of remodelling in wound healing

Answer 37

The skin remodels to diminish the appearance of scarring as far as possible.