general skin and fascia and osteology

mention functions of integument

mechanical barrier, 1st line of defense, UV protection

inmunological info

homeostasis, regulates body temp and water loss

sensory info

endocrine and excretion (sweat)

layers of the epidermis

stratum corneum - squamous keratinized tissue. anuclated and dead cells.

stratum lucidum (clear, water barrier, not always present, only in thick skin)

stratum granulosum (has keratohyalin filament bundles)

stratum spinosum - keratinocytes

stratum basale- stem cells, cuboidal

layers of the dermis

papillary layer (thin collagen) and reticular layer (thick collagen)

light skin

low melanin production and higher degradation

dark skin

high melanin production and lower degradation

blood supply of the skin

deep plexus, middle plexus and superficial plexus - then diffussion

free nerve endings

pain, touch, and temperature

meissner cells

light touch and mechanoreception

merkel cells

fine touch, fingertips

paccinian corpuscle

pressure and vibration (deep)

soft cornification

mammal and bird skin, interscale skin in reptiles

har cornificatiion

reptile skin, hair, claws, nails, feathers.

thick skin

dense and big epidermis (palms and plants)

skin modifications

thicker skin, lips, paw pads, nose, antlers. epidermis modifications.

skin appendages

hair, claws, sebaceous glands and sweat glands. extend dowwards from epidermis to dermis.

axial skeleton

central (skull and column)

skeletal system function

protection, blood production, storage, endocrine function (PTH, calcium, calcitonin), movement, immunity (b-cells)

osteoblast

progenitor cell, develops into osteocyte

osteocyte

mature bone cell, maintains bone

osteoclast

breakdown bone, macrophage

ECM of bone

hydrocyapatite, collagen, proteoglycans and GAGs

osteoid

new formed bone material - osteoblast becomes trapped and becomes osteocyte.

long bone

short bone

sesamoid bones

flat bones

irregular bones

intramembranous ossification

occurs in flat bones, from mesenchyme which secretes osteoid and forms diploe.

endochondreal ossification

occurs in long bones, cartilage works as a mold. there are 2 ossification centers, primary in diaphysis and secondary in the epiphysis. then remodeling. epiphyseal plate works for elongation.

steps of endochondreal ossification

resting cartilage, proliferation, hypertrophy and calcification.

wolffs law

remodeling of bone occurs according to the stress placed upon the bone.