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what are the types of loose connective tissue?
areolar tissue of loose connective
- cushions organs; provides support but permits independent movement; phagocytic cells provide defense against pathogens
- beneath dermis of skin, digestive tract, respiratory and urinary tracts
- most diverse of connective tissue
- provides padding and cushions shocks, insulates (reduces heat loss); stores energy
- deep to the skin at skides, buttocks, breasts
- provides supporting framework
- liver, kidney, spleen, lymph nodes and bone marrow
- uniform consistency
what are the types of dense connective tissue?
- regular (provides firm attachment; conducts pull of muscles; reduces friction between muscles, stabilizes relative positions of bones; located between skeletal muscles and skeleton
- irregular (provides strength to resist forces applied from many directions; helps prevent overexpansion of organs such as urinary bladder) anti-parallel
what is the difference between tendon and ligament
tendon connect muscle and bone; ligaments connect bone and bone
what are the types of supporting connective tissue?
cartilage and bone
what is cartilage?
- consists of a matrix of firm gel ground substance surrounding embedded fibers
- cells within the matrix (chondrocytes) are found in small pockets (lacunae)
what are all cartilage tissues covered by?
a perichondrium which contains an outer, givrous layer (for strength) and an inner, celular layer (for growth and maintenance)
what are the different types of cartilage?
what is hyaline cartilage?
provides stiff but somewhat flexible support, reduces friction between bony surfaces
what is chondrocyte?
cells within the matrix of firm gel ground substance (cartilages)
what is lacunae?
small pockets where chondrocytes are found
what is elastic cartilage?
provides suppport but tolerates distortion without damage and returns to original position; auricle of external ear
what is fibrocartilage?
- resists compression; prevents bone to bone contact; limits movment
- pads wihin knee joint, between pubic bones of pelvis and intervertebral discs
what is bone?
osseous tissue has a matrix composed o hard calcium componds (strong) and flexible collagen fibers (resists shattering) with virtually no ground substance
what is canaliculi?
small channels through bone matrix access blood supply
how are bone cells arranged?
osteocytes are arranged in lacunae around central canals within matrix
what is the integument?
composed of skin (cutaneous membrane with 2 epithelial layers) and accessory structures
where is hypodermis or subcutaneous layer located and is hypodermis part of skin?
located deep into the dermis; hypodermis is not part of skin just keeps the epithermis attached to the connective tissues beneath
what are the functions of the integument
- protection: prevents fluid loss and covers underlying tissues (water proof)
- temperature maintenance: skin regulates heat exchange with the environment
- synthesis and storage of nutrients: epidermis synthesizes vitamin D3. dermis stores lipids in adipose tissue
- sensory reception
- exretion and secretion
how would you classify the epithelia of the epidermis?
name the layers of the epidermis
- stratum corneum (very thick)
- stratum lucidum
- stratum granulosum (in feet and palms)
- stratum spinosum
- stratum basale
- basement membrane
what is the stratum basale?
- single layer of cells attached to basement membrane by hemidesmosomes
- forms epidermal ridges down into dermis (dermis has dermal papillae up into epidermis)
What is the importance of epidermal ridges and dermal papillae
- given that the epidermis is avascular, epidermal ridges and dermal papillae is needed to transfer nutrients
- increase in ridges and papillae increase nutrient uptake b/c of the increase in surface area
what is stratum spinosum?
the result of stem cell division
cells make a lot of keratin (a protein that provides water resistence and the foundation for hair and nails)
densely packed into a highly keratinized layer
contains 15-30 layers of keratinized or cornified dead cells connected via desmosomes (therefore shed in large groups)
what is the importance of vitamin D?
- derived from choleserol-related steroid in the epidermis when exposed to sunlight
- vitamin D is modified by liver and kidneys into calcitriol, essential for calcium and phosphorus absorption in the small intestine
- increases Ca+2 reabsorption by kidney
- promotes calcium deposition in bone
what two types of pigments are in epidermis?
- carotene: accumulates in epidermis
- melanin produced by melanocytes near stratus basales cells, absorbs UV to protect deeper layers
whats the relationship betwwen folate folic acid and vitamin D synthesis?
UVB promotes 90%of our vitamin D synthesis while UVA goes deeper and can cause Folic Acid (vitamin B9) breakdown
what are the three types of skin cancers?
- basal cell carcinoma: in stratum basale
- squamous cell carcinoma: found in more superficial layers
- malignant melanoma: begins with mole and can metacize thorugh lymphatic system
what are the two layers in the dermis?
- papillary: contains capillaries and nerves supplying the epidermis
- reticular: interwoven meshwork of dense, irregular connective tissue (elastic and collagen). Collagen fibers extend from up into the dermal papillae down into hypodermis
what is the hypodermis?
- aka subcutaneous layer
- stabilize skin to underlying tissues
- made of areolar tissue and many adipose cells
- no vital organs in area to make it ideal site for subcutaneous injections
what is hair papilla?
epithelium at the base of follicle caps over it
how are hair matrix formed?
epithelial stem cells divide
how are hair follicles formed?
epidermal layers invaginate into the dermis
what are sebaceous glands?
- secrete oily sebum into hair follicle
- holocrine (whole cell breaks down)
what are sebaceous follicles?
- secrete sebum directly into skin of face, back, chest, nipples
- sebaceous glands are sensitvie to hormonal changes
what are the two types of sweat glands of the skin?
what is apocrine sweat glands?
- become active at puberty and secrete sticky, cloudy sweat into hari follicles in armpits
- thought to function as olfactory pheromones
what are merocrine sweat glands?
- coiled tubular structures that secrete watery perspiration directly onto surface of skin
- sweat contains electrolytes, urea and organic nutrients
- function is to cool body through evaporation