Ch. 10: Homeostasis Flashcards
Excretory system
Serves many functions including regulation of BP, blood osmolarity, acid-base balance, and removal of nitrogenous wastes
Kidney
Produces urine, which dumps into the ureter at the renal pelvis. Contains a cortex and a medulla
Bladder
Urine is collected here until is is excreted
Urethra
Urine is excreted through this organ
Hilum
Each kidney has a hilum, which contains a renal artery, renal vein, and ureter
Portal System
The kidney contain a portal system with 2 capillary beds in series
Bowman’s capsule
Blood from the renal artery flows into afferent arterioles, which form glomeruli in Bowman’s capsule (the first capillary bed)
Nephron
Blood then flows through the efferent arteriole to the vasa recta, which surround the nephron (the second capillary bed), before leaving the kidney through the renal vein
Detrusor muscle
Bladder has a muscular lining known as detrusor muscle, under parasympathetic control– also has 2 muscular sphincters:
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
Filtration
Movement of solutes from blood to filtrate and Bowman’s capsule. The direction and rate of filtration is determined by starling forces which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space
Secretion
Movement of solutes from blood to filtrate anywhere other than Bowman’s capsule
Reabsorption
Movement of solutes from filtrate to blood
Segments of the Nephron
Proximal convoluted tubule (PCT) and Descending limb of the loop of Henle, diluting segment, Ascending limb of the loop of henle, distal convoluted tubule (DCT), collecting duct
Proximal convoluted tubule (PCT)
Site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt, and water. Also the site of secretion for hydrogen ions, potassium ions, ammonia, and urea
Descending limb of the loop of Henle
Permeable to water but not salt; therefore, as the 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
Ascending limb of the loop of Henle
Permeable to salt but not water; therefore salt is reabsorber both passively and actively
Diluting segment
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
Distal convoluted tubule (DCT)
Is 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 sys that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption. This results in an increased blood volume (and pressure) but no change in blood osmolarity
Antidiuretic hormone (ADH or vasopressin)
A peptide hormone synthesized by the hypothalamus and released by the posterior pituitary. Its release is stimulated not only by low blood volume but also by high blood osmolarity. It increases the permeability of the collecting duct to water, increasing water reabsorption. This results in an increased blood volume (and pressure) and a decreased blood osmolarity
Kidney regulation of pH
The kidney can regulate pH by selective reabsorption or secretion of bicarbonate or hydrogen ions
Skin
Acts as a barrier, protecting us from the elements and invasion by pathogens. Plays a role in thermoregualtion and prevents dehydration and salt loss from the body
Layers of the skin
Hypodermis (subcutaneous layer), dermis, and epidermis
Epidermis
composed of 5 layers: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
Stratum basale
Contains stem cells that proliferate to form keratinocytes
Stratum granulosum
Keratinocyte nuclei are lost in the stratum granulosum
Stratum corneum
Many thin layers form here
Melanocytes
Produce melanin
Melanin
Protects the skin from DNA damage caused by ultraviolet radiation; melanin is passed to keratinocytes
Langerhans cells
Special macrophages that serve as antigen presenting cells in the skin
Dermis
Composed of 2 layers: papillary layer and reticular layer
Sensory cells in the dermis:
Merkel cells, free nerve endings, Meissner’s corpuscles, Ruffini endings, and Pacinian corpuscles
Merkel cells
Deep pressure and texture
free nerve endings
Pain
Meissner’s corpuscles
Light touch
Ruffini endings
Stretch
Pacinian corpuscles
Deep pressure and vibration
Hypodermis
Contains fat and connective tissue and connects the skin to the rest of the body
skin cooling mechanisms
Include sweating, which absorbs heat from the body through evaporation of water from sweat, and vasodilation. Sweat glands are innervated postganglionic cholinergic sympathetic neurons
skin warming mechanisms
Include piloerection, in which arrector pili muscles contract, causing hairs to stand on end (trapping a layer of warmed air around the skin), vasoconstriction, shivering, and insulation provided by fat
