Biology Ch 10. Homeostasis Flashcards
Excretory system
Serves many functions including the regulation of blood pressure, blood osmolarity, acid base balance, and removal of nitrogenous wastes, consists of the kidneys, ureters, bladder, and urethra
Kidney
Two bean shaped structures located behind the digestive organs, produced urine, contains a cortex and a medulla, each has a hilium and portal system, participates in solute movement through filtration, secretion, and reabsorption, under hormonal control, can regulate pH by increasing or decreasing secretion of hydrogen ions and bicarbonate , functional unit is the nephron
Urine path
Kidney, ureter, bladder, urethra
Ureter
Transports urine from the kidney to the bladder to be stored, at the renal pelvis
Renal pelvis
Where all nephrons empty into that narrows into the ureter (ie the widest part of the ureter)
Bladder
Stores urine, has detrusor muscle and two sphincters
Urethra
Where urine is excreted
Hilium
Part of a kidney, deep slit in the center of the kidney’s medial surface, contains renal artery, renal vein, and ureter
Kidney portal system
Two capillary beds in series, the renal artery branches into afferent arterioles which then form glomeruli, after the glomeruli, blood passes to efferent arterioles
Bowmans capsule
Cuplike structurearound the glomerulus, in the first capillary bed blood from the renal artery in the medulla flows into afferent arterioles in the cortex which form glomeruli, leads to long tubule of the PCT, loop of henle, DCT and collecting duct
Vasa recta
Second capillary bed in the kidney, blood from efferent arterioles, surrounds the nephron, leave kidney in renal vein, surround the loop of henle
Detrusor muscle
Muscular lining in bladder, under parasympathetic control
Internal urethral sphincter
Consists of smooth muscle and is under involuntary/parasympathetic control
External urethral sphincter
Consists of skeletal muscle and is under voluntary control
Kidney filtration
The movement of solutes from blood to filtrate at Bowmans capsule, the direction and rate of filtration is determined by starling forces, hydrostatic pressure higher in the glomerulus so fluid moves into nephron, osmolarity higher in the glomerulus which opposes the movement of fluid into the nephron, net flow still from blood into nephron but rate will vary
Starling forces kidneys
Account for the hydrostatic and oncotic pressure differentials between the blood and Bowmans space
Kidney secretion
The movement of solutes from blood to filtrate anywhere other than Bowmans capsule by either active or passive transport, quantity and identify of substances secreted directly related to the needs of the body at that time, also a mechanism for excreting wastes that are simply too large to pass through glomerular pores
Kidney reabsorption
Movement of solutes from filtrate to blood, typically glucose, amino acids, and vitamins always reabsorbed, amount of water reabsorbed depends on ADH or aldosterone levels
Nephron segments
Proximal convoluted tubule, descending limb of the loop of Henle, ascending limb of the loop of Henle, distal convoluted tubule, collecting duct
Proximal convoluted tubule
PCT - The site of book reabsorption of glucose, amino acids, soluble vitamins, salt, and water (picked up by vasa recta and returned to blood stream), it is also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea, filtrate remains isotonic, in the kidney cortex
Descending limb of the loop of Henle
Permeable to water but not salt, therefore as filtrate moves into the more osmotically concentrated renal medulla, water is reabsorbed from the filtrate. the vasa recta and nephron flow in opposite directions creating a countercurrent multiplier system that allows maximal reabsorption of water, dives from cortex to inner medulla
Countercurrent multiplier system
System that allows the maximal reabsorption of water such as how the vasa recta and nephron flow in opposite directions, flow of the filtrate through the loop of Henle is in the opposite direction from the flow of blood through the vasa recta, therefore, filtrate constantly exposed to hypertonic blood
Ascending limb of the loop of Henle
Permeable to salt but not water, therefore 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 the blood
Diluting segment
Transition from inner to outer medulla where the loop of Henle gets thicker, cells in the lining are larger because they contain large amounts of mitochondria, allows for maximum reabsorption of sodium and chloride by active transport, filtrate becomes hypotonic, only part of nephron capable of producing urine more dilute than the blood (important for overhydration)
Distal convoluted tubule
DCT - Responsive to aldosterone and is a site of salt reabsorption (water goes with the salt) 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, last site of secretion/reabsorption
Kidney response to low blood pressure/volume
Both aldosterone and antidiuretic hormone hormonal systems are activated
Aldosterone
A steroid hormones regulated by the renin-angiotensin-aldosterone system that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption. This results in increased blood volume and pressure but no change in blood osmolarity, also increases potassium and hydrogen ion excretion
Antidiuretic hormone
ADH - aka vasopressin - a peptide hormone synthesized by the hypothalamus and released by the posterior pituitary, it’s release is stimulated not only by low blood volume but also buy high blood osmolarity, it increases the permeability of the collecting duct to water increasing water reabsorption. This results in increased blood volume and pressure and a decreased blood osmolarity
Kidney pH regulation
Can you still buy selective reabsorption and secretion of bicarbonate or hydrogen ions
Kidney cortex
Kidney’s outermost layer
Kidney medulla
Sits within the cortex of the kidney
Glomeruli
Highly convoluted capillary tufts derived from afferent arterioles
Afferent arterioles
Arterioles that flow into kidney’s first capillary bed, form glomeruli, in medulla of kidney
Efferent arterioles
Arterioles that flow into kidney’s second capillary bed or vasa recta, in medulla of kidney
Micturition reflex
When the bladder is full and stretch receptors cause parasympathetic neurons to fire, detrusor muscle contracts, this causes the internal sphincter to relax; however, urination does not occur unless the individual relaxes the external sphincter also with voluntary control
Osmoregulation
Primary job of the kidneys, done by filtration, secretion, and reabsorption
Filtrate
Collected fluid that is filtered from the blood to Bowmans space
Interstitium
Connective tissue surrounding the nephron, where molecules are reabsorbed to be sent back to vasa recta
Filtrate from beginning to end of nephron
Beginning - isotonic
End - volume significantly reduced, hypotonic (filtrate has been diluted)
Renin-angiotensi-aldosterone pathway
Decreased blood pressure - > release of renin from juxtaglomerular cells in the kidney - > renin cleaves angiotensinogen to angiotensin I -> angiotensin I metabolized by angiotensin-converting enzyme in the lungs to angiotensin II -> promotes release of aldosterone from the adrenal cortex
Juxtaglomerular cells
Cells in the kidney that release renin in response to low blood pressure
Angiotensinogen
A liver protein that is cleaved to angiotensin I by renin
Angiotensin I
Peptide cleaved from angiotensinogen by renin
Angiotensin-converting enzyme
Enzyme in the lungs which metabolizes angiotensin I to angiotensin II
Angiotensin II
Promotes the release of aldosterone from the adrenal cortex, metabolized from angiotensin I
Osmotic presssure
The sucking pressure that draws water into the vasculature caused by all dissolved particles
Oncotic pressure
The osmotic pressure that is attributable to dissolved proteins specifically
Low blood osmolarity
Excess water excreted, solutes reabsorbed in higher concentrations
High blood osmolarity
Water reabsorption increases, solute excretion increases
Bicarbonate buffer system
CO2(g) + H2O = H2CO3 = H+ + HCO3-
major regulator of blood pH
Skin
aka integument, largest organ in body, acts as a barrier, protecting us from the elements and invasion by pathogens (part of the nonspecific immune defense), important for thermoregulation, prevents dehydration and salt loss from the body, derived from the ectoderm
Skin layers
Hypodermis (deepest), dermis (middle), epidermis (surface)
Epidermis layers
Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum, called strata
Stratum basale
Bottom layer of the epidermis, contains stem cells that proliferate to form keratinocytes, also home to melanocytes
Stratum granulosum
Layer of epidermic, where keratinocytes die and lose their nuclei
Stratum corneum
Layer of the epidermis, made of many thin layers of flattened keratinocytes, forms barrier that prevents pathogen invasion or fluid/salt loss
Melanocytes
Produce melanin, derived from neural crest cells, found in stratum basale
Melanin
Pigment that protects the skin from DNA damage caused by ultraviolet radiation, pigment is passed to keratinocytes after being produced
Langerhans cells
Special macrophages that serve as antigen-presenting cells in the skin, reside in stratum spinosum
Dermis layers
Papillary layer and the reticular layer
Dermis sensory cell types
Merkel cells, free nerve endings, Meissners corpuscles, Ruffini endings, and Pacinian corpuscles
Merkel cells
Sensory cell that senses deep pressure and texture
Free nerve endings
Sense pain
Meissners corpuscles
Sensory cell that sense light touch
Ruffini endings
Sensory cell that sense stretch
Pacinian corpuscles
Sensory cell that senses deep pressure and vibration
Hypodermis
Contains fat and connective tissue, connects the skin to the rest of the body
Thermoregulation cooling mechanism
Sweating and vasodilation
Sweating
Draws heat away from the body through evaporation of water from swear
Sweat glands
Innervated by postganglionic cholinergic sympathetic neurons
Thermoregulation warming mechanism
Piloerection, vasoconstriction, shivering, and insulation provided by fat
Piloerection
Arrector pili muscles contract causing hairs to stand on end (traps a layer of warmed air around the skin)
Keratinocytes
Predominant cells in the skin, produce keratin, proliferate in stratum basal, become connected to each other in stratum spinosum, die in stratum granulosum
Keratin
Created by keratinocytes, resistant to damage and provides protection against injury, water, and pathogens , also forms fingernails and hair
Startum spinosum
Keratinocytes become connected to each other, site of langerhans cells, layer of epidermis
Stratum lucidum
Only present in thick, hairless skin (sole of foot and palms), nearly transparent, layer of epidermis
Calluses
Form from excessive keratin deposits in areas of repeated strain due to friction
Fingernails and hair
Formed by keratin and produced by specialized cells
Papillary layer
Upper layer of the dermis that consists of loose connective tissue
Reticular layer
Lower layer of the dermis
Dermis
Divided into papillary and reticular layer, where sweat glands, blood vessels, and hair follicles originate, where most sensory receptors are located
Brown fat
Tissue found especially in infants that has a much less efficient ETC and more heat energy is released as fuel is burned
