The integumentary system Flashcards
What are the 7 functions of the skin?
Protection
Regulation of body temperature
Sensation
Immune defence
Excretion
Vitamin D synthesis
Water regulation
Endocrine function
Describe the skins role in protection
It acts as a physical barrier, protecting the body from physical, chemical, and biological hazards such as UV radiation, pathogens, and toxins.
Describe the skins role in body temperature regulation
The skin helps regulate body temperature through processes like sweating (evaporative cooling) and vasoconstriction/dilation of blood vessels (heat conservation or dissipation).
Describe the skins role in sensation
The skin contains numerous sensory receptors that detect touch, pressure, pain, and temperature, allowing us to perceive and respond to stimuli from the environment.
Describe the skins role in immune defence
Specialized immune cells in the skin, such as Langerhans cells and dendritic cells, help protect against pathogens and foreign substances by initiating immune responses.
Describe the skins role in excretion
Sweat glands in the skin excrete waste products, such as urea and salts, helping to regulate electrolyte balance and eliminate toxins from the body.
Describe the skins role in vitamin d synthesis
When exposed to sunlight, the skin produces vitamin D, which is essential for calcium absorption and bone health.
Describe the skins role in water regulation
The skin helps prevent excessive loss of water from the body through its barrier function, helping to maintain hydration and prevent dehydration.
Describe the skins role in Endocrine function
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
What is the dermis
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.
What is the dermis composed of?
Blood vessels
Lymphatic vessels
Nerves
Sweat glands
Sebaceous glands
Hair follicles
Immune cells - macrophages, mast cells, fibroblasts
What is the function of fibroblasts and where are they found?
In the dermis
They produce collagen and elastin fibers which contribute to the structural integrity and flexibility of the skin
What is the function of the papillary dermis and where is it located
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
What is the function and location of the reticular dermis
It’s the deeper thicker layer of the dermis, consisting of dense irregular connective tissue that provides strength, support, and elasticity to the skin
What is the epidermis
It is the outermost layer of the skin
What is the epidermis composed of
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
What are the layers found in the epidermis
Stratum basale (or basal layer) - deepest layer
Stratum spinosum
Stratum granulosum
Stratum corneum - outermost layer
What is the stratum basale composed of?
Actively dividing cells responsible for replenishing outer layers of the epidermis
What is the stratum corneum composed of and where can it be found?
The outermost layer of the epidermis, and is composed of dead keratinocytes (keratinized cells) that provide protection against physical and environmental damage
Whats the structure and function of hair?
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.
Whats the structure of a nail?
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).
Whats the function of a nail?
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.
Describe the process of wound healing
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
What are the chemical barriers of the skin in relation to protection?
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
What are the physical/mechanical barriers of the skin in relation to protection?
Keratinisation: provides a hard impenetrable barrier (tight junctions and desmosomes act as physical barriers)
What are the biological barriers of the skin in relation to protection?
Langerhans cells (from bone marrow) when presented with antigens produce immune response. Macrophages (from blood) engulf debris and bacteria
Explain how temperature regulation is maintained through homeostasis using the skin
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.
What are the two types of sensory cutaneous receptors and what do they respond to?
Meisseners corpuscles in the dermal papillae respond to gentle touch
Pacinian corpuscles (in the deeper dermal layer and hypodermis) respond to deep pressure
What are the 3 metabolic functions of the skin?
Calcium metabolism, detoxifaction of carcinogens and conversion of steroids
Explain calcium metabolisation & the link with vitamin D
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
Explain how the skin carries out detoxification of carcinogens
Keratinocyte enzymes can metabolise and render harmless many cancer causing chemicals
Explain how the skin carries out conversion of steroids
Keratinocytes can convert cortizone applied topically into hydrocortisone which is an anti-inflammatory
Describe the process and steps of inflammation in wound healing
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
Describe the process and steps of granulation in wound healing
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
Describe the process and steps of regeneration in wound healing
Epithelium begins to regenerate.
Epithelial cells migrate across granulation tissue just beneath scab (which then detaches)
Describe the process and steps of remodelling in wound healing
The skin remodels to diminish the appearance of scarring as far as possible.
