Ch 10 - Homeostasis

Question 1

excretory system functions

Answer 1

• blood pressure
• blood osmolarity
• acid base balance
• nitrogenous waste removal

Question 2

Kidney Strucutre

Answer 2

• Cortex - outermost
• Medulla - innermost
• contains a portal system
  
  • renal artery enters and becomes afferent arterioles
  • glomeruli are capillary beds that form off of afferent arterioles
  • efferent arterioles remove the blood which then forms a capillary bed (vasa recta) around the loops of henle
• bowmans capsule - surrounds glomerulus
  
  • leads to proximal convoluted tubule, descending and ascending loop of henle, distal convoluted tubule, collecting duct

Question 3

Bladder

Answer 3

• detrusor muscle - muscular lining
  
  • controlled by parasympathetic NS
• micturition reflex - detrusor muscle contracts and internal sphincter relaxes
  
  • individual controls the external sphincter (skeletal muscle)

Question 4

Filtration in Kidneys

Answer 4

• filtrate - fluid that passes through the glomerulus into Bowmans capsule
  
  • Starling forces - pressure differential in hydrostatic and osmotic pressures between blood and Bowmans capsule
  • higher hydrostatic pressure in glomerulus forces it into the bowmans capsule
  • higher oncotic pressure in blood then bowmans capsule
  • hydrostatic pressure out completes oncotic pressure
    
    • flow into nephron
• molecules/cells larger than glomerular pores remain in blood
  
  • remaining blood goes to efferent arterioles then vasa recta
• filtrate isotonic to blood

Question 5

Secretion

Answer 5

• movement of solutes from blood to filtrate anywhere besides Bowman’s capsule
• secrete salts, acids, bases, urea into tubule
• eliminate substances in excess
• also way to excrete large waste that does not pass through glomerulus

Question 6

Nephron Function

Answer 6

• Filtrate enter proximal convoluted tubule (PCT)
  
  • amino acids, glucose, watersoluble vit, and salts are reabsorbed (water follows these)
  • leave PCT, enter interstitium, enter vasa recta
• descending loop of Henle - deeper into medulla (higher interstitium conc.), only permeable to water
• most concentrated filtrate at the bottom of Henle
• ascending loop of Henle - only permeable to salts, impermeable to water
  
  • diluting segment - thicker tubule as it comes out of medulla
    
    • thicker to accomidate mitochondria for active transport and reabsorption of Na and K
  • hypotonic filtrate at times
• Distal convoluted tubule (DCT) - waste product secretion, water follow sodium
  
  • respond to aldosterone which reabsorbs Na
• Collecting duct - responsive to aldosterone and ADH
  
  • concentrates the urine
• Overall Countercurrent multiplier system - vasa recta and nephron gradients work to make max. diffusion and reabsorption

Question 7

Blood pressure control - kidney

Answer 7

• Aldosterone - steroid hormone, from adrenal cortex due to decreased blood pressure
  
  • Juxtaglomerular cells release Renin when low blood pressure
  • renin cleaves angiotensinogen to make angiotensin I
  • Angiotensin I to Angiotensin II via angiotensin converting enzyme in the lungs
  • Angiotensin II promotes release aldosterone
• aldosterone alters DCT and collecting duct to reabsorb sodium
  
  • also increases K+ and H+ excretion
• Antidiuretic Hormone (ADH) - peptide hormone made by hypothalamus and released by post. pituitary
  
  • released due to high blood osmolarity
  • causes more reabsorption of water in collecting duct

Question 8

Osmotic vs oncotic pressure

Answer 8

• osmotic - sucking pressure caused by all dissolved particles
• oncotic - osmotic pressure due to dissolved proteins

Question 9

acid base balance via kidney

Answer 9

• increase or decrease secretion of H+ and HCO3-
• slower than respiratory, but effective
• Bicarbonate buffer system

Question 10

Epidermis

Answer 10

• Come Lets Get Sun Burned
• Stratum Corneum - layers of flat keratinocytes to form barrier. Prevent water loss
• Stratum Lucidum - in thick, hairless skin
• Stratum Granulosum - keratinocytes die and lose nuclei
• Stratum Spinosum - connect cells, Langerhans cells
• Stratum Basale - stem cells, keratinocytes that produce keratin

Question 11

Cells of epidermis

Answer 11

• keratinocytes - produce keratin
  
  • calluses - excessive keratin
  • fingernails and hair
• melanocytes - from neural crest, in stratum basale
  
  • produce melanin
  • blacks have more active melanocytes
• Langerhans cells - special macrophages

Question 12

Dermis/Hypodermis

Answer 12

• Dermis -
  
  • papillary layer - upper layer
  • reticular layer
  • sweat glands, blood vessels, hair follicles originate in dermis
  • Merkel cells - deep pressure and texture sensation
  • free nerve endings - pain
  • Meissner’s corpuscles - light touch
  • Ruffini endings - respond to stretch
  • Pacinian corpuscles - deep pressure and vibration
• hypodermis - connect skin to body, fat and fibrous

Question 13

Thermoregulation via skin

Answer 13

• sweating
• piloerection - to form air layer on skin and stay warm
• vasodilation - to lose heat
• vasoconstriction - to keep heat