the integumentary system Flashcards
what are the functions of the skin?
-protection
-regulation of body temp
-sensory perceptions
-synthesis of vitamin D
-excretion and absorption
-serves as an important reservoir of blood
how does the skin help with the regulation of body temperature?
by liberating sweat and adjusting blood flow to the demis
what is the structure of the skin?
-it has 2 major layers
-the outer, thinner layer is the epidermis and consists of the epithelial tissue and is vascular
-the inner, thicker layer is the dermis and conostst pf C.T and is vascularised
what is the subQ layer?
-the subcutaneous layer, it is underneath but not part if the skin and is a loose areolar/dispose C.T that attaches the skin to the underlying tissues and organs
what is the epidermis composed of?
-keratinized stratified squamous epithelium that contains 4 major types of cells
what are the 4 major types of cells the keratinised stratified squamous epithelium consists of?
-keratinocytes
-melanocytes
-langerhans cells
-merkel cells
what do keratinocytes do?
-produce keratin which provides protection
what do melanocytes do?
-produces melanin which helps protect against damage by UV
what do langerhan cells do?
-they are macrophages which are involved in immune responses
what do merkel cells do?
-they are tactile receptors that have a function in the sensation of touch along with other adjacent tactile discs
how many layers in thin and thick skin is the epidermis composed of?
-4 layers in thin skin
-5 layers in thick skin
what is the stratum corneum?
-it is composed of 25 layers of flathead keratinocytes that are like bags of turtle wax with no cellular organelles filled with only keratin protein
what is the stratum lucidum?
-it has 4-6 layers of dead keratinocytes
-it is the 4th layer but is only present in thick skin (skin of the fingertips, pals and soles)
what is the stratum granulosum?
-it is 3-5 layers of flattened keratinocytes undergoing apoptosis and they are filled with granules of keratin
-they release lamellar granules which are lipid rich secretion that acts as a water repellant sealant
what does the stratum spinosum consist of?
-a layer of 8-10 keratinocytes
what does the stratum basal consist of?
-cuboidal or columnar keratinocytes
-it is always the bottom, deepest layer
-stem cell division produces new keratinocytes
what happens to newly formed cells in the stratum basale?
-they are pushed to the surface and accumulate more and more keratin (this is the process of keratinisation)
-they can also undergo apoptosis and slough off and be replaced by underlying cells
what are the different types of skin?
-thin hairy skin (4 layers) which covers all body regions except the palms, palmar surfaces of digits and soles
-thick hairless skin (5 layers inc the stratum lucidium) covers the palms, palmar surfaces of digits and soles
what is melanin produced by?
-melanocytes in the stratum basale and it dictates skin colour
-it can accumulate in patches, freckles or liver spots
-it can either be eumelanin (brown/black polymer) or pheomelanin (yellow/red polymer)
what is nevi?
-nevi is birthmarks/moles and they are chronic benign lesions of the skin caused by an overgrowth of melanocytes
what is malignant melanoma?
-a cancer of melanocytes
what is albinism?
-a congenital disorder characterised by an inability to produce melanin nd is missing from the skin, hair and eyes
what is vitiligo?
-a chronic depigmentation disorder,there is a partial or complete loss of melanocytes from patches of skin produces irregular white spots
what does the dermis do?
-it provides temperature stability and provides dehydration
-it is composed of dense irregular connective tissue containing collagen and elastic fibres
-it contains two regions
what are the two regions of the dermis?
-papillary region
-reticular region
how is the papillary region?
-it lies just below the epidermis and consists of areolar connective tissue
how is the reticular region?
-it consists of dense irregular connective tissue, hair,follicles,nerves,sebaceous (oil) and sudoriferous (sweat) glands
what does the subcutaneous layer/hypodermis do?
-insulates and stores fat
-attaches the skin to underlying tissues and organs
-contains blood vessels and nerves in transit to the more superficial layers
what do sensory receptors do?
-they help differentiate between tactile sensations e.g light, touch,pressure,virbration,itch and tickle
what are the different types of receptors?
-superficial touch receptors are merkel discs, free nerve endings,meissner corpuscles, hair root plexuses
-deep receptors are pacinian corpuscles
where is hair present?
-on most surfaces except the palms, anterior surfaces of fingers and the soles of feet
what does hair do?
-it is composed of columns of dead, keratinised epidermal cells and helps with touch sensations and protects the body from harmful effects of the sun and against heat loss
-hair colour is determined by the amount and type of melanin
what are the different exocrine hair glands?
-sudoriferous (sweat glands)
-ceruminous glands
what are the two types of sudoriferous (sweat glands)?
-eccrine sweat glands
-apocrine sweat glands
what are sebaceous (oil) glands?
-they are oil glands that are connected to hair follicles
-they secrete an oily substance called sebum which helps prevent dehydration of skin and inhibits bacteria
how are eccrine sweat glands?
-they appear on the forehead ,palms and soles
-they secrete a water solution (600ml per day) and it helps to cool the body and eliminates all amounts of waste
how are appocrine sweat glands?
-they appear on the skin of the axilla (armpit),groin, areolae (pigmented ares around the nipples) of the breasts and breaded regions of the face in adult males
-they secret a slightly viscous sweat which is responsible for body odour
how are ceruminous glands?
-they are modified sweat glands located in the ear canal
-it produces a waxy secretion called cerumen (earwax)
what are the functions of nails?
-they protect the distal end of the digits
-they provide support and counter pressure to the palmar surface of the fingers to enhance touch perception and manipulation
-they allow us to grasp and manipulate small objects and they can be used to scratch and groom the body in various ways
when does epidermal wound healing occur?
-following superficial wounds that affects only the epidermis (abrasions or minor burns)
-skin damage sets in motion a sequence of events that repairs the skin to its normal (or near normal) structure and function
when does deep wound healing occur and what can deep wounds cause?
-it occurs when an injury extends to the dermis and subcutaneous layer
-it can cause a loss of some function and the development of scar tissue
what are the 4 phases of the process of deep wound healing?
-inflammatory phase
-migratory phase
-proliferative phase
-maturation phase
what are burns?
-burns involve tissue damage caused by denaturation (break down) of the proteins in the skin cells by excessive heat, electricity,radiation or corrosive chemicals
what happens in a first degree burn?
-it involves only the epidermis and is characterised by mild pain and erythema (redness) but no blisters and skin functions remain intact
what happens in second degree burns?
-it destroys the epidermis and part of the dermis, some skin functions are lost but there can be redness, blister formation,edema and pain that can be a result of these burns
what happens in 3rd degree burns?
-they are full thickness burns, it destroys the epidermis, dermis and subcataneous layer, most skin functions ar lost and the region is numb because sensory nerve endings have been destroyed
what are the functions of the bone and skeletal system?
-it supports soft tissues and provides attachment points for tendons of skeletal muscle
-assistance in movement-skeletal muscle attaches to bone
-blood cell production-red bone marrow produces blood cells
-mineral homeostasis
-protection
-triglyceride storage
what is the function of the bone and skeletal system in protection?
-it helps protect important internal organs
-the cranium protects the brain
-the vertebrae protects the spinal cord
-the ribs protect the lungs and heart
wha is the function of bones and the skeletal system in mineral homeostasis?
-bone tissue stores several minerals
-calcium (is 99% of the body’s content)
-phosphorus
what role does the bone and skeletal system play in triglyceride storage?
-yellow bone marrow stores triglycerides
what is the structure of bone?
-it begins with metaphayses,then the articular cartilage,then the periosteum
how is the metaphyses?
-it contains an epiphyseal (growth) plate, a layer of hyaline cartilage that allows the diaphysis of the bone to grow in length
-when a bone ceases to grow in length (14-24) the cartilage in the epiphyseal plate is replaced by bone, the epiphyseal line
what is the articular cartilage?
-it covers part of the epiphysis where the bone forms an articulation (joint) with another bone
-it reduces friction and absorbs shock at freely movable joints
what is the periosteum?
-tough connective tissue sheath that surrounds the bone wherever it is not covered by articular cartilage
-outer fibrous layer of dense irregular connective tissue and an inner osteogenic layer that consists of osteoprogenitor cells
what is the histology of bone (osseous tissue)?
-the cells in bone tissue are surrounded by extracellular matrix, the matrix its 15% water,30% collagen fibers and 55% crystallised mineral salts
what is the most abundant mineral salt in the histology of bone?
-calcium phosphate
what is calcification?
-where crystallised mineral salts deposited in the framework formed by the collagen fibres of the extracellular matrix become harder as they crystallise and this makes bone hard
what is hardness and flexibility in the bone caused by?
-hardness is due to crystallised inorganic mineral ssalts
-flexibility is due to collagen fibres
what are the 4 types of cells in bone tissue?
-osteogenic
-osteoblasts
-osteocytes
-osteoclasts
what are osteogenic cells?
-stem cells that can undergo cell division resulting in an osteoblast
what are4 osteoblasts?
-bone building cells, they synthesise and secrete collagen fibres
what are osteocytes?
-mature bone cells that maintain daily bone metabolism
what are osteoclasts?
-huge cells derived from many white blood cells involved in development,maintenance and repair
-it is also involved homeostasis
how is bone tissue organised?
-in concentric bone lamellae around an osteonic canal in compact bone and in irregularly arranged bone lamellae in the bone trabecular in spongy bone
what are the factors affecting bone growth?
-minerals
-vitamins
-hormones
how does minerals affect bone growth?
-large amounts of calcium and phosphorus are needed for bone growth
what does vitamin D do?
-stimulates osteoblast activity
what is vitamin C required for?
-collagen synthesis
what is vitamin D required for?
-calcium absorption from foods
what is vitamin K and B12 used for?
-bone protein synthesis
how do vitamins affect bone growth?
-IGF (insulin like growth factors produced by the liver and bone)-stimulate osteoblasts and promote cell division
-sex hormones-oestrogen and testosterone stimulate osteoblast activity and growth during puberty
what are the two main ways that blood calcium levels can be increased?
-release of calcium from bone matrix
-retention of calcium by the kidneys
what is calcium homeostasis require for?
-nerve and muscle function
-blood clotting
-blood level regulation at 9-11mg/100 ml
how does bone help buffer calcium levels?
-by releasing Ca2+(osteoclasts)
-by absorbing Ca2 (osteoblasts)
what doe the parathyroid hormone (PTH) do?
-it is secreted by parathyroid glands and when calcium levels drop the PTH detects this and increases the activity of osteoclasts to release Ca2+ via negative feedback
what does calcitonin do?
-it is secreted by parafollicular cells of thyroid
-it decreases blood Ca2+ by inhibiting osteoclast activity and enhancing osteoblast activity
