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MCAT Bio. Ch. 10

Functions Of The Excretory System Include: Regulation of blood pressure, blood osmolarity, acid-base balance, and removal of nitrogenous wastes
The Kidney Produces Urine, Which Dumps Into: The ureter at the renal pelvis. Urine is then collected in the bladder until it is excreted through the urethra.
The Kidney Contains: A cortex and a medulla.
Each Kidney Has A Hilum, Which Contains: A renal artery, renal vein, and ureter
The Kidney Contains A Portal System With: Two capillary beds in series
Blood From The Renal Artery Flows Into: Afferent arterioles, which form glomeruli in Bowman's capsule (the first capillary bed)
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
The Bladder Has a Muscular Lining Known As The: Detrusor muscle which is under parasympathetic control. It also has two muscular sphincters.
Internal Urethral Sphincter Of Detrusor Muscle: Consists of smooth muscle and is under involuntary (parasympathetic) control
External Urethral Sphincter Of Detrusor Muscle: Consists of skeletal muscle and is under voluntary control
Filtration Of Kidney: Movement of solutes from blood to filtrate at 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 Of Kidney: Movement of solutes from blood to filtrate anywhere other than Bowman's capsule
Reabsorption Of Kidney: Movement of solutes from filtrate to blood
Proximal Convoluted Tubule (PCT): Site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt, and water. Also, this is 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, which creates 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 reabsorbed both passively and actively.
Diluting Segment Of Ascending Loop Of Henle Is Located: 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 Is 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 Is: A steroid hormone regulated by the renin-angiotensin-aldosterone system that increases sodium reabsorption in the distal convoluted tubule and collecting duct, thereby increasing water reabsorption.
Aldosterone's Effect Of Increasing Water Reabsorption Results In: An increased blood volume (and pressure), but no change in blood osmolarity
Antidiuretic Hormone (ADH or Vasopresin) Is: 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.
Effect Of Antidiuretic Hormone (ADH or Vasopresin): 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.
The Kidney Can Regulate pH By: Selective reabsorption or secretion of bicarbonate or hydrogen ions
The Skin Acts As A: Barrier in order to protect us from the elements and invasion by pathogens
Skin Is Composed Of Three Layers Which Include: The hypodermis (subcutaneous layer), dermis, and epidermis
The Epidermis Is Composed Of Five Layers: The stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
Stratum Basale Contains: Stem cells that proliferate to form keratinocytes. Keratinocyte nuclei are lost in the stratum granulosum, and many thin layers form in the stratum corneum.
Melanocytes Produce: Melanin, which protects the skin from DNA damage caused by ultraviolet radiation. Melanin is passed to keratinocytes.
Langerhans Cells Are: Special macrophages that serve as antigen-presenting cells in the skin.
The Dermis Is Composed Of Two Layers: The papillary layer and the reticular layer
Many Sensory Cells Are Located In The Dermis, Including: Merkel cells (deep pressure and texture), free nerve endings (pain), Meissner's corpuscles (light touch), Ruffini endings (stretch), and Pacinian corpuscles (deep pressure and vibration)
The Hypodermis Contains: Fat and connective tissue and connects the skin to the rest of the body
The Skin Is Important For Thermoregulation Which Is: The maintenance of a constant internal temperature
Cooling Mechanisms Of The Skin Include: Sweating, which absorbs heat from the body through evaporation of water from sweat, and vasodilation. Sweat glands are innervated by postganglionic cholinergic sympathetic neurons.
Warming Mechanisms Of The Skin 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
The Skin Also Prevents: Dehydration and salt loss from the body
Created by: SamB91