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University of Toronto Scarborough
Biological Sciences

Read pg. 22 Radiological Procedures -noninvasive techniques using radioisotopes, radiation, magnetic fields to produce images of internal structures -ppl who do this are called radiologists -gives detailed info about internal systems and structures X-ray -high energy radiation that can penetrate living tissues -strikes a photographic plate -Not all projected x-rays arrive at the film. Some are absorbed or deflected as they pass through the body -resistance to x-ray penetration is called radiodensity - (least radiodensity) air, fat, liver, blood, muscle, bone (most radiodensity) - Bone becomes white, less dense things are black Barium-contrast X-ray -barium is very radiodense CT scans - used to be called CAT (computerized axial tomography) - Uses a single x-ray source rotating around the body - X-ray strikes a sensor monitored by a computer - Source completes 1 rev/few seconds - Get a 3D structure of body Digital subtraction angiography (DSA) - for blood flow in organs like brain, heart, lungs, kidneys - xrays taken before and after radiopaque dye used and computers subtracts details from both Spiral CT scan - xrays rotate around person, less radiation, faster MRI -surrounds body with magnetic field, 3000x stronger then earth - affects protons, line up along magnetic lines -protons absorb energy with proper frequency...pulse ends=energy released Ultrasound -brief, narrow burst of high frequency sound, picks up echoes -sound waves reflected by internal structure -picture/echoegram showen Pg. 104-105 Sweat glands  Skin has two types: apocrine and merocrine o both contain myoepithelial cells (specialized epithelial cells located btw the gland cell and basal lamina) o myoepithelial cell contractions squeeze the gland and discharge the accumulated secretions o the secretory activities of the gland cells and the contractions of myoepithelial cells are controlled by both autonomic nervous system and circulating hormones  Apocrine Sweat glands o Release their secretions into hair follicles in the axillae (armpits), nipples (areolae), and groin o Not really apocrine secretion, moreso merocrine o Coiled, tubular, and produce viscous, cloudy, odourous (due to bacteria) secretion o Begin secreting at puberty o May also contain pheromones o Secretions in mature women may alter menstrual timing of other women  Merocrine/Eccrine Sweat glands o More numerous, widely distributed, smaller o In adults, about 3 million o Don’t extend as far into the dermis as apocrine o Mostly on palms and soles o Coiled, tubular, discharge secretions directly onto surface of skin o Produces sweat (sensible perspiration)  99% water, electrolytes (NaCl)=salty taste, metabolites, waste o Thermoregulation  Sweat cools skin surface, reduces body temperature  Regulated by neural and hormonal mechanisms o Excretion  For water and electrolytes, drugs o Protection  From environmental hazards by diluting harmful chemicals and discouraging the growth of microorganisms  Sebaceous glands and apocrine sweat glands can be turned on and off by autonomic nervous system, no regional control (all become activated)  Merocrine sweat glands are more precisely controlled, and the amount of secretion and area of body involved can be varied independently. (when u wait for exam, palms sweat) Repairing Injuries to the Skin  Skin regenerates because of stem cells in both epithelial and connective tissue components  Germinative cell divisions replace lost epidermal cells  Mesenchymal cell divisions replace lost dermal cells 1. Damage extending through epidermis into dermis=bleeding. Mast cells trigger inflame response 2. Blood clot/scab forms to temporarily restore epidermis and restricts microorganisms. Clot consists of insoluble network of fibrin. Colour of clot due to trapped RBC. Cells of stratum basale migrate along edge of wound replacing missing epidermal cells. Phagocytic (macrophages) cells remove debris. Dermal repairs must occur before epithelial cells can cover. Fibroblasts and mesenchymal cells produce mobile cells invading deeper. Endothelial cells of damaged blood vessels divide, capillaries follow fibroblasts, enhancing circulation. a. Granulation tissue-combo of blood clot, fibroblast, capillary network 3. One week after injury, scab has been undermined by epidermal cells migrating over meshwork produced by fibroblast activity. Phagocytic activite around site almost done, fibrin clot disintegrating…a lot of collegen fibers and few blood vessels 4. Several weeks later, scab sheds, epidermis is complete. Fibroblasts in dermis continue to create scar tissue that gradually elevate the overlying epidermis. Scar tissue considered a practical limit to healing process. a. Keloid=thick, raised area of scar tissue Pg. 46-49 cell cycle - The two most important steps in cell division o DNA replication-duplication of cells genetic material o Mitosis-distribution of one copy of genetic info to two daughter cells - Interphase o Cell doing normal things, preparing o G1 (normal functions, growth, duplicate organelles, protein syn), S (DNA replication), G2 (Protein synthesis) - Prophase o Chromosomes coil tightly, 2 copies of chromosomes (chromatids) connected at the centromere o Two pairs of centrioles that were replicated in G1 began to move apart o Spindle fibers extend btw centriole pairs o Astral rays radiate into cytoplasm o Nuclear envelop disappears o Chromosomal microtubule-kinetochore attach to spindle fiber - Metaphase o Kinetochore attached to chromosomal microtubule o Move to metaphase plate - Anaphase o Daughter chromosomes move to opposite poles at centrioles - Telophase o Cell returns to interphase state. o Nuclear membrane forms, nucleus enlarges, chromosome uncoils o Nucleoli reappear - Cytokinesis o Usually
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