Anatomy Final

  1. Urinary System
    Consists of 2 kidneys, 2 ureters, urinary bladder, and urethra
  2. Kidneys
    • Filter the blood plasma and excrete the toxic metabolic wastes
    • Regulate blood volume, pressure, and osmolarity by regulating water output
    • Regulate electrolyte and acid-base blanace of body fluids
    • Secrete the hormone erythropoietin, which stimulates the production of red blood cells and thus supports the oxygen-carrying capacity of blood
    • Help regulate calcium homeostasis and bone metabolism by participating in the synthesis of calcitriol
    • Clear hormones and drugs from the blood and limit their action
    • In extreme starvation, they help support the blood glucose level by synthesizing glucose from amino acids
  3. Metabolic Waste
    • A waste substance produced by the body
    • Nitrogenous wastes
  4. Nitrogenous Wastes
    • Most toxic of our metabolic wastes
    • Small nitrogen-containing compounds
    • 50% is urea, a by-product of catabolism
    • Proteins are hydrolyzed to amino acids, and then the -NH2 group is removed from each amino acid
    • NH2 is converted into ammonia which the liver quickly turns into urea
    • Uric acid and creatinine
    • -Produced by the catabolism of nucleic acids and creatine phosphate
    • Levels expressed as blood urea nitrogen
    • -10-20 mg/dL
  5. Azotemia
    • An elevated blood urea nitrogen
    • May indicate renal insufficiency
    • Can progress to uremia
    • Treatment can entail hemodialysis or organ transplant
  6. Uremia
    • A syndrome of diarrhea, vomiting, dyspnea, and cardiac arrhythmia stemming from the toxicity of the nitrogenous wastes
    • Convulsions, coma, and death can follow in the next few days
  7. Excretion
    • The process of separating wastes from the body fluids and eliminating them
    • Carried out by 4 organ systems
    • -Respiratory
    • -Integumentary
    • -Digestive
    • -Urinary
  8. Excretion: Respiratory System
    Excretes carbon dioxide, small amounts of other gases, and water
  9. Excretion: Integumentary System
    Excretes water, inorganic salts, lactic acid, and urea in sweat
  10. Excretion: Digestive System
    Actively excretes water, salts, carbon dioxide, lipids, bile pigments, cholesterol, and other metabolic wastes
  11. Excretion: Urinary System
    Excretes a broad variety of metabolic wastes, toxins, drugs, hormones, salts, hydrogen ions, and water
  12. Kidney Layers
    • Protected by 3 layers of connective tissue
    • Fibrous renal fascia, immediately deep to the parietal peritoneum, binds it to abdominal wall
    • Perirenal fat capsule, cushions it and holds it in place
    • Fibrous capsule, encloses it anchored at the hilium, and protects it from trauma and infection
  13. Renal Parenchyma
    • Glandular tissue that forms the urine
    • Encircles the renal sinus
    • Divided into 2 zones
    • -Outer renal cortex
    • -Inner renal medlla
  14. Renal Sinus
    • Occupied by blood and lymphatic vessels, nerves, and urine-collecting structures
    • Adipose tissue fills the remaining space and holds all of it in place
  15. Renal Cortex
    Has extensions called renal columns that divide the medulla into 6-10 renal pyramids
  16. Renal Circulation
    Receive about 1.2 liters of blood per minute or 21% of the cardiac output
  17. Renal Artery
    Divides into a few segmental arteries that divide into a few interlobar arteries
  18. Interlobar Arteries
    • Penetrates each renal column and travels between the pyramids toward the corticomedullary junction
    • Branches to form arcuate arteries which give rise to several cortical radiate arteries which give rise to afferent arterioles
  19. Nephron
    • Contains 2 parts
    • -Renal corpuscle
    • -Renal tubule
  20. Renal Corpuscle
    • Consists of the glomerulus and a 2-layered glomerular capsule that encloses it
    • Outer layer is simple squamous epithelium and inner layer consists of elaborate cells called podocytes
    • At opposite side there is a vascular and urinary pole
  21. Vascular Pole
    • Afferent arteriole enters the capsule, bringing blood to the glomerulus
    • Efferent arteriole leaves the capsule and carries blood away
    • Has a large inlet and small outlet
  22. Urinary Pole
    • Parietal wall of the capsule turns away from the corpuscle, giving rise to the renal tubule
    • Simple squamous epithelium becomes simple cuboidal in the tubule
  23. Renal Tubule
    • A duct that leads away from the glomerular capsule
    • Divided into 4 regions
    • -Proximal convuluted tubule
    • -Nephron loop
    • -Distal convoluted tubule
    • -Collecting duct
  24. Proximal Convoluted Tubule
    • Arises from the glomerular capsule
    • Longest and most coiled, therefore dominates histological sections of renal cortex
    • Has simple cuboidal epithelium with microvilli
    • A lot of absorption occurs here
  25. Nephron Loop
    • Found mostly in the medulla
    • Divided into think and thin segments
    • Thick segments have a simple cuboidal epithelium and form the intial part of the descending limb and part or all of the ascending limb
    • -Active transport of salts, so have high metabolic activity and are full of mitochondria
    • Thin segments have a simple squamous epithelium and have a low metabolic activity, but is very permeable to water
  26. Distal Convoluted Tubule
    • Short and less coiled
    • Cuboidal epithelium with smooth-surfaced cells
    • End of nephron
  27. Collecting Duct
    • Receives fluid from the DCTs of several nephrons as it passes back into the medulla
    • Merge to form a larger papillary duct
    • Urine drains from pores into the minor calyx
    • Lined with simple cuboidal epithelium
  28. Cortical Nephrons
    • Just beneath the renal capsule, close to the kidney surface
    • Short nephron loops
    • Some have no nephron loops at all
  29. Juxtamedullary Nephrons
    • Close to the medulla
    • Have very long nephron loops
    • Solely responsible for maintaining an osmotic gradient that helps the body conserve water
  30. Renal Plexus
    • Wrapped around each renal artery
    • Carries sympathetic innervation from the abdominal aortic plexus and afferent pain fibers
    • Stimulation of sympathetic fibers reduce glomerular blood flow, increase rate of urine production, and respond to falling blood pressure by secreting renin
  31. Kidneys
    • Converts blood plasma to urine in 4 stages
    • -Glomerular filtration
    • -Tubular reabsorption
    • -Tubular secretion
    • -Water conservation
  32. Glomerular Filtration
    • Similar to blood plasma, but has no protein
    • Fluid in the capsule space
    • Water and some solutes in the blood plasma pass from capillaries of the glomerulus into the capsular space of the nephron
    • Passes through 3 barriers that constitute a filtration membrane
    • -Fenestrated endothelium of the capillary
    • -Basement membrane
    • -Filtration slits
  33. Fenestrated Endothelium of the Capillary
    • Endothelial cells have large filtration pores
    • Highly permeable
    • Pores small enough to exclude blood cells from filtrate
  34. Basement Membrane
    • Has a proteoglycan gel
    • Few particles may pepntrate its small spaces, but most would be held back
    • Excludes molecules larger than 8nm
    • Some particles are held back by a negative charge in the proteoglycan gel
    • Has traces of albumin and smaller polypeptides, including some hormones
  35. Filtration Slits
    • A podocyte
    • Has a bulbous cell body and several thick arms
    • Each arm has little extensions called foot processes
    • Have negatively charged to help prevent large anions
  36. Filtration Membrane
    • Almost any molecule smaller than 3nm can pass through
    • Water, electrolytes, glucose, fatty acids, amino acids, nitrogenous wastes, and vitamins
    • Kidney infections and trauma can damage it, allowing albumin or blood cells to filter through
  37. Filtration Pressure
    • Blood hydrostatic pressure is much higher here
    • Has a larger afferent arteriole and a smaller efferent arteriole
    • Hydrostatic pressure of 18mmHg from high rate of filtration and continual accumulation of fluid in capsule
    • Colloid osmotic pressure is the same
    • Glomerular filtrate is almost protein free
  38. Hypertension
    • Ruptures glomerular capillaries and leads to scarring of the kidneys
    • Promotes atherosclerosis of the renal blood vessels, thus diminishes renal blood supply
    • Often leads to renal failure which leads to worsening of this
    • -A positive feedback loop
  39. Glomerular Filtration Rate
    • The amount of filtrate formed per minute by the 2 kidneys combined
    • Males= 125mL/min or 180 L/day
    • Females= 105mL/min or 150 L/day
    • Average adult reabsorbs 99% of filtrate
  40. High Glomerular Filtration Rate
    • Fluid flows through the renal tubules too rapidly for them to reabsorb the usual amount of water and solutes
    • Urine output rises and creates a threat of dehydration and electrolyte depletion
  41. Low Glomerular Filtration Rate
    • Fluid flows sluggishly through the tubules
    • Reabsorbs wastes that should be eliminated in the urine and azotemia may occur
  42. Renal Autoregulation
    • The ability of the nephrons to adjust their own blood flow and GFR without external control
    • Enables them to maintain a stable GFR in spite of changes in arterial blood pressure
    • Helps ensure stable fluid and electrolyte balance
    • 2 mechanisms
    • -Myogenic mechanism
    • -Tubuloglomerular feedback
  43. Myogenic Mechanism
    • Based on the tendency of smooth muscle to contract when stretched
    • When arterial blood pressure rises, it stretches the afferent arteriole
    • Arteriole constricts and prevents blood flow into the glomerulus from changing very much
    • When arterial blood pressure falls, the afferent arteriole relaxes and allows blood to flow more easily into the glomerulus
  44. Tubuloglomerular Feedback
    • The glomerulus receives feedback on the status of the downstream tubular fluid and adjusts filtration to regulate its composition, stabilize nephron performance, and compensate for fluctuations in blood pressure
    • Has a structure called the juxtaglomerular apparatus
    • 3 Cells
    • -Macula densa
    • -Juxtaglomerular cells
    • -Mesangial cells
    • If GFR rises, it increases the flow of tubular fluid and rate of NaCl reabsorption by the PCT
  45. Macula Densa
    • A patch of slender, closely spaced epithelial cells at the end of the nephron loop on the side facing the arterioles
    • If GFR rises, they sense variations in flow or fluid composition and secrete a paracrine messenger that stimulates JG cells
  46. Juxtaglomerular Cells
    • Enlarged smooth cells in the afferent arteriole
    • Directly across from the macula densa
    • When stimulated, the dilate or constrict arterioles
    • Contain granules of renin, which is secreted in response to a drop in blood pressure
    • Initiates the renin-angiotensin-aldosterone mechanism which raises blood pressure
  47. Mesangial Cells
    • Cells in the cleft between the afferent and efferent arterioles and among capillaries of the glomerulus
    • Connected to the macula densa and JG cells by gap junctions
    • Communicate by paracrine secretions
    • Build a supportive matrix for the glomerulus, constrict or relax its capillaries to regulate blood flow and GFR, and phagocytize tissue debris
  48. Sympathetic Control of Glomerular Filtration
    • Richly innervate the renal blood vessels
    • In streneous exercise or acute conditions like circulatory shock, stimulation and adrenal epinephrine constrict the afferent arterioles
    • Reduces GFR and urine output while redirecting blood from the kidneys to the heart, brain, and skeletal muscles, where it is more needed
  49. Renin-Angiotensin-Aldosterone Mechanism
    • When blood pressure drops because of bleeding, sympathetic fibers stimulate the JG cells to secrete renin
    • Renin acts on angiotensinogen to make angiotensin I
    • In the lungs and kidneys, angiotensin-converting enzyme removes 2 or more amino acids, converting it to angiotensin II
  50. Angiotensin II
    • Potent vasoconstrictor that raises the mean arterial blood pressure throughout the body
    • In kidneys, it constricts the efferent arterioles raising the glomerular blood pressure and GFR
    • Stimulates the adrenal cortex to secrete aldosterone, which promotes water reabsorption
    • Stimulates posterior pituitary gland to secrete ADH
    • Stimulates the sense of thirst and encourages water intake
Card Set
Anatomy Final