Flashcards in Chapter 5: The Integumentary System Deck (124)
Two main parts of the skin
Superficial thin epidermis (epithelial tissue) and deep thick dermis (connective tissue)
What are the 6 functions of the integumentary system?
1) Regulates body temp, 2) Stores blood, 3)Protects body from external env 4) Detects cutaneous sensations, 5) Excretes and absorbs substances, 6) Synthesizes vitamin D
What is the function of the subcutaenous layer (hypodermis)?
Has areolar and adipose tissue. Storage depot for fat and contains large blood vessels that supply the skin.Also contains nerve endings called LAMELLATED CORPUSCLES (which are sensitive to pressure).
What are the 4 main types of cells of the epidermis?
Keratinocytes, melanocytes, intraepidermal macrophages, and tactile epithelial
What do keratinocytes do?
Arranged in 4-5 layers. Account for 90% of epi cells. produce the protein KERATIN (protects the skin and tissues from abrasions, heat, water loss, microbes and chemicals) and produces LAMELLAR GRANULES (releases a water repellant sealant which decreases water entry and loss and inhibits the entry of foreign materials).
What are melanocytes and what do they do?
Produces the pigment MELANIN. Long slender projections between keratinocytes and transfer melanin granules to them. Contibutes to skin colour and absorbs UV light. When inside keratinocytes, melanin granules cluster to form a protective veil over the nucleus (to shield the nuclear DNA from UV damage)
What do intraepidermal macrophages do?
AKA Langerhans cells. Arise from red bone marrow and migrate to epidermis. Participates in the immune responses mounted against microbes that invade the skin. Easily damaged by UV. Helps other cells of immune system recognize an invading microbe and destroy it.
What are tactile epithelial cells?
Least numerous epidermal cells. Deepest layer of epidermis. Contact the flattened process of a sensory neuron, a structure called a TACTILE DISC... detects touch sensations
What are the 4 strata/layers in most epidermis?
Stratum basale, stratum spinosum, stratum granulosum, and thin stratum corneum (thin skin)
Wat are the 5 layers/strata of the epidermis where exposure to friction is greatest (ie fingertips, palms, soles)?
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum and a thick stratum corneum (thick skin)
What is the stratum basale composed of?
A single row of cuboidal columnar keratinocytes. Some cells are stem cells and produce new keratinocytes
What are keratin intermediate filaments?
In the stratum basale. They are in the cytoskeleton within keratinocytes and form the tough protein keratin in its more superficial layer. They attach to desmosomes which bind cells of the stratum basale to eachother and to the cells of the adjacent stratum spinosum and to hemidesmosomes, which bind the keratinocytes to the basement membrane between the epidermis and dermis
What is the stratum spinosum composed of?
Mostly consists of many keratinocytes arranged in 8-10 layers... cells in more superficial layers are somewhat flattened. Keratinocytes provide the stratum spinosum which are produced by the stem cells in the basal layer. The keratinocytes of this later produce coarser bundles of keratin in intermediate filaments. Under the miscroscope looks like cells of the stratum spinosum are covered with thorn-like spines. At each spinelike projection, bundles of keratin intermediate filaments insert into desmosomes which tightly join the cells together... provides strength and flexibility to skin. Intraepidermal macrophages and projections of melanocytes also present
What makes up the stratum granulosum?
3.5 layers of flattened keratinocytes that undergo apoptosis. The nuclei and other organelles of these cells begin to degenerate as they move further from their source of nutrition (dermal has blood vessels). A feature of cells in this layer are darly staining granules of a protein called KERATOHYALIN which assembles keratin intermediate filaments into keratin. Also present in the keratinocytes are membrane-enclosed lamellar granules which fuse with the plasma membrane and release lipid-rich secretion which is deposited in the spaces between cells of the stratum granulosum, stratum lucidum and stratum corneum ..... acts as water-repellent seal. Therefore the stratum granulosum marks the transition between deeper metabollically active strata and the dead cells of the superficial strata
What is the stratum lucidum made up of?
Only present in areas like fingertips, palms and soles (thick skin). 4-6 layers of flattened dead keratinocytes that contain lots of keratin and thickened plasma membranes.
What is the stratum corneum made of?
25-30 layers of flattened dead keratinocytes. Cells are thin flat plasma membrane-enclosed packages of keratin that no longer contain a nucleus or other organelles. Final profuct of the differentiation processes of keratinocytes. Cells continuously shed and replaced by cells in deeper strata
Describe the keratinization and growth of epidermis
Newly formed cells in the stratum basale are slowly pushed to the surface. As Cells move from one epidermal layer to the next, they accumulate more and more keratin (a process called KERITANIZATION) then they undergo apoptosis. Cells form in the stratum basale, become keratinzed and slough off which takes 4-6 weeks. The cells in the dermis produce the most keratinocytes via cell division because they have the most access to blood supply
What is dermis composed of?
Dense irregular connective tissue containing collagen and elastic fibres. Great tensile strength (resists pulling and stretching). Stretches and recoils more easily. Has mainly fibroblasts and some adipocytes near its boundary with the subcutaneous layer. Blood vessels, nerves, glands, and hair follicles are embedded in the dermal layer. Dermis is essential to survival of epidermis.
What are the 2 regions of the dermis?
The thin superficial PAPILLARY REGION and thick deeper RETICULAR REGION
What's in the papillary region of the dermis?
Thin collagen and fine elastic fibres. SA increased by dermal papillae which are small nipple shaped structures that project into the undersurface of the epidermis. All dermal papillae contain capillary loops and some contain tactile receptor called corpuscles of touch (nerve endings sensitive to touch) or free nerve endings (dentrites that lack any apparent structural specialization)... initiates signals that give rise to sensations of warmth, coolness, pain, tickling and itching.
What is the reticular region of the dermis?
Attached to the subcutaneous layer, hasb undles of thick collagen fibres, scattered fibroblasts and wandering cells (ie macrophages). Also has some adipose cells and coarse elastic cells in the deepest layer. Collagen fibres in a more regular arrangement that those in papillary region... which helps resist stretching. Blood vessels, nerves, hair follicles, oil glands, sweat glands occupy the spaces between fibres. The collagen and elastic fibres in this region give the skin extensibility (ability to stretch) and elasticity.
What are the 3 pigments that impart a variety of colours to the skin?
1) Melanin, 2) hemoglobin 3) carotene
What are the two forms of melanin?
Pheomelanin (yellow/red) and eumelanin (brown and black)
Where are melanocytes most plentiful?
Epidermis of penis, nipples of breasts, area around nipples (areola), face, and limbs
WHat are age spots?
An accumulation of melanin in patches... builds up overtime due to exposure of sunlight
What is a mole/nevus?
A round, flat or raised area that is a localized growth of melanocytes
How do melanocytes synthesuze melanin?
Melanocytes synthesize melanin from the amino acid tryonise in the presence of the enzyme tyrosinase. Synthesis occurs in an organelle called MELANOSOME
What does exposure toUV light do to enzymes?
Exposure to UV light increases enzymatic activity within melanosomes so increases melanin production (tanned)
What are the functions of melanin?
Absorbs UV radiation, prevents damage to DNA and neutralizes free radicals. Small amounts of UV radiation necessary to start process of DNA synthesis