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Excretory system
functions to regulate blood pressure, blood osmolarity, acid-base balance and removal of nitrogenous waste
kidney
produces urine
which flows into the ureter at the renal pelvis. Urine is then collected in the bladder until excreted through the urethra
contain a cortex and hilum which contains renal artery, renal vein and ureter.
portal system [kidney]
2 capillary beds
blood from the renal artery flows into afferent arterioles which form glomeruli in the bowman’s capsule (1st capillary bed)
blood then flows through the efferent arteriole to the vasa recta (second capillary bed) which surround the nephron before leaving the kidney through the renal vein
bladder
detrusor muscle (muscular lining) under parasympathetic control
internal urethral sphincter
external urethral sphincter
internal urethral sphincter
consist of smooth muscle, under involuntary (parasympathetic control)
external urethral sphincter
consists of skeletal muscle, under voluntary control
3 solute movement processes [kidney]
filtration
secretion
reabsorption
filtration
movement of solutes from blood to filtrate at bowman’s capsule
direction and rate of filtration is determined by starling forces, which accounts for the hydrostatic and oncotic pressure differentials between the glomerulus and bowman’s space
secretion
movement of solutes from blood to filtrate anywhere other then bowman’s capsule
reabsorption
movement of solutes from filtrate to blood
Proximal convoluted tubule
site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt and water.
site of secretion for hydrogen ions, potassium ions, ammonia and urea
descending loop of henle
permeable to water but not salt
filtrate moves into the more osmotically concentrated renal medulla, water is reabsorbed from the filtrate.
vasa recta and nephron flow in opposite directions creating a countercurrent multiplier system that allows maximal absorption of water
ascending loop of Henle
permeable to salt but not water
salt is reabsorbed both passively and actively.
the diluting segment is in the outer medulla, because salt is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to blood.
distal convoluted tubule
responsive to aldosterone and is a site of salt reabsorption and waste product excretion like the PCT
Collecting duct
responsive to both aldosterone and antidiuretic hormone and has variable permeability which allows reabsorption of the right amount of water depending on the body’s needs
aldosterone [steroid hormone]
regulated by the renin-angiotensin-aldosterone system
that increases sodium reabsorption in the DCT and collecting duct thereby increase water reabsorption.
results in increase blood volume and pressure [no change in blood osmolarity]
kidney can regulate PH by selective reabsorption or secretion of bicarbonate or hydrogen ions
skin
acts as a barrier protecting us from elements and invasion by pathogens
prevents dehydration and salt loss from the body
3 major layers of the skin
epidermis (top)
dermis
hypodermis
5 layers of the epidermis
stratum basale
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum (top)
stratum basale
contains stem cells that proliferate to form keratinocytes
melanocytes
produce melanin which protects the skin from DNA damage by ultraviolet radiation
melanin is passed to keratinocytes
langerhans cells
special macrophages that serves as antigen-presenting cells in the skin
dermis
papillary layer
reticular layer
sensory cells located in the dermis
merkel cells (deep pressure and texture)
free nerve endings (pain)
Meissner’s corpuscles (light touch)
rufffini endings (stretch)
pacinian corpuscles (deep pressure and vibration)
hypodermis
contains fat and connective tissue
also connects the skin to the rest of the body
vasodilation
cooling mechanism,
eg sweating, sweat glans innervated by postganglionic cholinergic sympathetic neurons
vasoconstriction
piloerection, arrector pili muscles contract casuing hairs to stand
shivering and insulation provided by fat
renin-angiotensin-aldosterone system (RAAS)
a crucial hormone system that regulates blood pressure, fluid, and electrolyte balance by controlling sodium and water reabsorption, vascular tone, and the release of aldosterone