Skin Structure Flashcards
What is the integumentary system
Aka skin
Largest organ of the human body
An Epithelial membrane - cutaneous
What are the three layers of the skin
- Superficial = epidermis
- Middle = dermis
- Subcutaneous / adipose
What is the epidermis layer of the skin
Formed of tightly packed epithelial tissue cells which is keratinised epithelium (protective & waterproof)
Interstitial fluid (situated in between cells) provides oxygen & nutrients to cells, slow diffusion from dermis
Epidermis is drained by lymph
No blood vessels (avascular) & no nerve endings
What is found in the dermis layer of the skin
Formed of connective tissue, matrix of collagen (strength) & elastic fibres (stretch & recoil)
Thickest layer in skin
contains accessory structures such as sweat glands, hairs, arrector pili muscles & sebaceous glands
Arterioles & capillaries (thermoregulation)
Lymph vessels & sensory nerve endeings
Fibroblasts & immune cells - macrophages & mast cells
What is the subcutaneous layer of skin
An insulating & protective layer of fatty tissue that connects the dermis to deeper lying muscle & bone
How does the keratinised epithelium of the epidermis form
Watery round cells produced at the bottom of the epidermis rise to the surface, gradually flattening
Accumulating keratin for waterproofing, this suffocates the cells causing our outer epidermis layers to be made entirely of dead cells
What are the types of cells found in the epidermis
90% keratinocytes - tough fibrous protein that protects from heat, microbes & chemicals
8% melanocytes - pigment that contributes to skin colour & absorbs UV light. Melanin granules surround the nuclei of keratinocytes on skin surface side
2% langerhan’s cells - immune cells involved in antigen presentation
What is eumelanin
Type of melanin that contributes to brown/black colour
What is pheomelanin
Melanin that contributes to red/yellow colour
What is the structure of fingerprints
Ridges that form in 3rd month of foetal development
Increase surface area & enhances grip by creating friction
What are the meissner’s corpuscle sensory nerves
Nerves in the dermis that are Sensitive to light pressure
What are the pacinian corpuscle sensory nerves
Found in the dermis and are sensitive to deep pressure
What are the free nerve endings in the dermis
Sensitive to pain & temperature
What are the structure of the hairs of the dermis
Concentric columns of dead keratinised cells bonded together by proteins
Contains melanin pigments which contributes to colour
A microscopic band of smooth muscle called ARRECTOR PILI connect the hair follicle to the dermis
When the hair is erect, it traps a layer of air next to the skin which contributes to thermoregulation
What are sebaceous glands
Glands in the dermis that secrete sebum which keeps hairs soft, provides water-proofing & is anti-microbial
Activity increases with puberty & decreases with age
Fatty acids in sebum inhibit bacterial growth
What are the main functions of the skin
Protection Thermoregulation Vitamin D production Sensation Absorption Excretion
What is desquamation
The shedding of skin cells helps remove microbes
What simulates sweat glands & blood vessels in the skin
The autonomic nervous system via the hypothalamus & medulla oblongata (brain stem)
How does our skin form vitamin D
UV light activates a vitamin D precursor in the skin from cholesterol
The kidneys convert the precursor to calcitrol
Calcitrol acts as a hormone to increase uptake of calcium & phosphorus from food into blood, thus ultimately supporting bone density
Vitamin D is stored in the liver
What is the process of superficial wound healing
Eg abrasions/burns
Basal cells move across the gap until contact inhibition occurs
Epidermal growth factor causes multiplication of the basal cells until space is filled
What is contact inhibition
Cessation of cell division in cells once they are touching eachother
What is the process of deep wound healing
When affecting dermis &or subcutaneous
- Inflammatory phase - migration of leukocytes, blood clot forms & scabs, epithelial cells migrate to repair membrane
- Proliferative phase - granulation tissue is formed with the laying of collagen & blood vessels, extensive growth & repair of epithelial cells
- Remodelling phase - 3 weeks-6 months, scab naturally falls off & scar tissue remains
What is a hypertrophic scar
Stays within the boundary of the wound
Contains less hairs, glands, nerve endings & blood vessels hence paler appearance
What is a keloid scar
Takes up a larger space than the wound (normally raised)
Also contains less cells
