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Human Physiology > Unit 4 > Flashcards

Unit 4 Flashcards

1
Q

What functions of the Urinary System contribute to homeostasis?

A
  • Excretion of Wastes
  • Regulation of Blood Volume
  • Regulation of Blood Pressure
  • Regulation of Blood pH
  • Regulation of Blood Composition
  • Regulation of Blood Osmolarity
  • Production of Hormones
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2
Q

Composition: Urinary System

A
  • Kidneys
  • Ureters
  • Urinary Bladder
  • Urethra
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3
Q

Urine

A

The fluid produced by the kidneys that contains wastes (and other excess materials) and is excreted from the body via the urethra.

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4
Q

How do the kidneys excrete wastes from the body?

A

The kidney forms (and facilititates the excretion of) urine that contains nitrogenous wastes and unwanted foreign substances.

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5
Q

Nitrogenous Wastes

A

Nitrogen-containing waste products that are by-products of metabolic reactions.

Ex: Ammonia, Urea, Uric Acid, Creatinine, Urobilin

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6
Q

How do the kidneys regulate blood ionic composition?

A

The kidneys adjust the amounts of certains ions (Na+, K+, Ca2+, Cl–, HPO42-) excreted into the urine.

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7
Q

How do the kidneys regulate blood pH?

A

The kidneys excrete variable amounts of hydrogen ions (H+) into the urine AND conserve variable amounts of of bicarbonate ions (HCO3–) within the blood.

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8
Q

How do the kidneys regulate blood volume?

A

The kidneys return water to the blood OR eliminate water via the urine.

This movement of water between the blood and the urine also regulates blood pressure.

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9
Q

How do the kidneys regulate blood pressure?

A
  • The kidneys return water to the blood (to increase blood pressure) OR eliminate water via the urine (to decrease blood pressure).
  • The kidneys secrete Renin to activate the Renin-Angiotensin-Aldosterone pathway (to increase blood pressure).
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10
Q

How do the kidneys regulate blood osmolarity?

A

The kidneys separately regulate water loss (to the urine) and solute loss (to the urine) to maintain a relatively constant blood osmolarity.

Blood osmolarity is maintained at roughly 300 milliosmoles/liter.

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11
Q

Which hormones are produced by the kidneys?

A
  • Calcitriol: Regulation of Calcium Homeostasis.
  • Erythropoietin: Stimulation of Erythrocyte Production
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12
Q

Kidney

A

A paired organ (located near the lower back) that produces urine and regulates blood composition/volume/pressure/osmolarity/pH.

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13
Q

Retroperitoneal

A

Located Behind the Peritoneum

The kidneys are retroperitoneal.

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14
Q

Two Regions of the Kidney

A
  • Renal Cortex: Superficial Region
  • Renal Medulla: Inner Region
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15
Q

Renal Pyramids

A

Cone-shaped structures within the renal medulla that lead/drain into the minor/major calyces.

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16
Q

Minor Calyx vs. Major Calyx

A
  • Minor Calyx: Smaller cuplike structure that unite to form a major calyx.
  • Major Calyx: Larger cuplike structure composed of mulitple minor calyces.
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17
Q

Renal Pelvis

A

A large cavity that originates at a major calyx and drains/leads into a ureter.

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18
Q

Path of Urine through the Urinary System

A
  1. Kidney
  2. Ureters
  3. Urinary Bladder
  4. Urethra

Within the Kidney: Renal Pyramids → Minor Calyx → Major Calyx → Renal Pelvis

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19
Q

What are the functional units of the kidneys?

A

Nephrons

Nephrons are located in the renal cortex and the renal medulla.

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20
Q

Nephron: Two Main Components

A
  • Renal Corpuscle
  • Renal Tubule
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21
Q

Renal Corpuscle

A

The site of blood plasma filtration that consists of the glomerulus and the Bowman’s capsule.

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22
Q

Glomerulus

A

A rounded mass/network of blood capillaries enclosed within the Bowman’s capsule.

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23
Q

Bowman’s Capsule

Glomerular Capsule

A

A double-layered epithelial cup at the begining of a nephron that encloses the glomerulus.

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24
Q

Renal Tubule

A

A tubelike structure consisting of a single layer of epithelial cells that extends from the renal corpuscle and drains into the collecting duct.

The renal tubule consists of the proximal tubule, Loop of Henle, and distal tubule.

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25
Q

Which portion(s) of the nephron are located in the renal cortex?

A
  • Renal Corpuscle
  • Proximal Tubule
  • Distal Tubule
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26
Q

Which portion(s) of the nephron are located in the renal medulla?

A

Loop of Henle

  • The Loop of Henle’s descending loop extends into the renal medulla.
  • The Loop of Henle’s ascending loop returns to the renal cortex.
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27
Q

Proximal Tubule

A

A convoluted portion of the renal tubule that extends from the renal corpuscle and leads into the Loop of Henle.

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28
Q

Loop of Henle

Nephron Loop

A

The portion of the renal tubule that receives fluid from the proximal tubule and transmits fluid into the distal tubule.

The Loop of Henle is a hairpin loop that consists of a descending limb and an ascending limb.

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29
Q

Distal Tubule

A

A convoluted portion of the renal tubule that extends from the Loop of Henle and drains into the collecting duct.

Several distal tubules (of multiple nephrons) drain into a single collecting duct.

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30
Q

Collecting Duct

A

A ductlike structure that collects fluid/flitrate from the distal tubules and drains fluid/filtrate into the minor calyces.

Once the filtrate exits the collecting duct, it is referred to as urine (since its composition can no longer be altered).

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31
Q

Afferent Arteriole

A

A small artery that receives blood from the Renal Artery and delivers blood to a glomerulus (of one nephron).

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32
Q

Efferent Arteriole

A

A small artery that carries blood away from the glomerulus and divides to form the peritubular capillaries.

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33
Q

What makes the glomerular capillaries unique among capillaries?

A

The glomerular capillaries are positioned between two arterioes (rather than one arteriole and one venule).

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34
Q

Peritubular Capillaries

A

Capillaries that receive blood from the efferent arteriole and eventually unite to give rise to the Renal Vein.

Peritubular capillaries surround the renal tubules (proximal tubule + Loop of Henle + distal tubule) of cortical nephrons.

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35
Q

Juxtaglomerular Apparatus

JGA

A

A cellular mass consisting of the macula densa and juxtaglomerular cells that secretes Renin (when blood pressure falls) to increase blood pressure.

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36
Q

Macula Densa

A

A crowded mass of epithelial cells of the distal tubule that is located adjacent to the afferent/efferent arteriole.

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37
Q

Nephrons: Three Basic Functions

A
  • Glomerular Filtration
  • Tubular Reabsorption
  • Tubular Secretion
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38
Q

Glomerular Filtration

First Step of Urine Production

A

The water and solutes of blood plasma move across the glomerular capillary walls and into the Bowman’s capsule space.

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39
Q

Tubular Reabsorption

Second Step of Urine Production

A

The cells of the renal tubule and collecting duct (and eventually the peritubular capillaries) reabsorb the vast majority of water and solutes initially filtered (in the Bowman’s capsule) as the filtered fluid flows through the nephron.

Reabsorption: The movement of substances from the tubular lumen fluid to the peritubular capillary blood.

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40
Q

Tubular Secretion

Third Step of Urine Production

A

The cells of the renal tubule and collecting duct secrete wastes and foreign substances (from the bloodstream) into the tubular lumen as the filtered fluid flows through the nephron.

Secretion: The transfer of substances from the peritubular capillary blood to the tubular lumen fluid.

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41
Q

Location: Filtration vs. Reabsorption vs. Secretion

A
  • Filtration: Renal Corpuscle
  • Reabsorption: Throughout Renal Tubule
  • Secretion: Throughout Renal Tubule
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42
Q

Bowman’s Capsule: Structure

A
  • Parietal Layer: The Capsule’s outer layer that consists of a single layer of epithelial cells continuous with the renal tubule’s epithelial cells.
  • Visceral Layer: The Capsule’s inner layer that consists of a single layer of modified epithelial cells (Podocytes) with footlike processes (Pedicels).
  • Bowman’s Space: The space between the Capsule’s parietal layer and visceral layer that is continuous with the renal tubule lumen.
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43
Q

Glomerular Filtrate

A

The fluid produced in the Bowman’s space by the filtration of blood (through the filtration membrane) in the renal corpuscle.

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44
Q

How is the composition of glomerular filtrate comparable to the composition of blood?

A

Glomerular filtrate is comparable to blood plasma (i.e. the acellular component of blood) without without the plasma proteins.

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45
Q

Filtration Membrane

A

A leaky barrier formed by the Glomerulus and Bowman’s capsule visceral layer that permits the filtration of water and small solutes (but not blood cells or plasma proteins) into the Bowman’s space.

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46
Q

Filtration Membrane: Three Layers

A
  • Glomerulus Endothelium
  • Glomerulus Basement Membrane
  • Bowman’s Capsule Visceral Layer (Podocyte Filtration Slits)
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47
Q

What causes the leakiness of the Glomerular endothelial cells?

A

Glomerular endothelial cells possess fenetrations/pores large enough to permit the passage of water and solutes (from blood plasma).

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48
Q

Glomerulus Basement Membrane

A

A porous layer of acellular material between the Glomerulus endothelium and visceral layer Podocytes that consists of collagen fibers and negatively charged glycoproteins.

  • The pores of the basement membrane allow for the passage of water and small solutes.
  • The negatively charged glycoproteins of the basement membrane repel plasma proteins.
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49
Q

What feature of the filtration membrane inhibits the filtration of plasma proteins?

A

Negatively charged glycoproteins of the Glomerulus basement membrane and the Capsule’s Podocyte layer repel the anionic plasma proteins (to inihibit passage into the Bowman’s space).

The small size of the filtration slit pores (between the Podocyte pedicels) also inhibits the filtration of plasma proteins into the Bowman’s space.

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50
Q

Filtration Slits

A

The spaces between Podocyte pedicels (of the Bowman’s capsule visceral layer) that are covered by a slit membrane containing 6–7 nm pores.

The pores of the slit membrane allow the passage of water, glucose, vitamins, hormones, amino acids, urea, ammonia, and ions.

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51
Q

Why is the volume of fluid filtered through the glomerulus much larger than the volume filtered in other capillaries of the body?

A
  • The glomerular capillaries create a much larger surface area for filtration to occur (due to their long and extensive structure).
  • The filtration membrane is thinner (only 0.1 mm thick) and more porous (possessing many large fenestrations).
  • The glomerular capillary blood pressure is higher (because the efferent arteriole has a smaller diameter than the afferent arteriole).
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52
Q

Four Pressures Determining Glomerular Filtration

A
  • Glomerular Capillary Hydrostatic Pressure (Promotes Filtration)
  • Bowman’s Space Colloid Osmotic Pressure (Promotes Filtration)
  • Bowman’s Space Hydrostatic Pressure (Opposes Filtration)
  • Blood Plasma Colloid Osmotic Pressure (Opposes Filtration)
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53
Q

Glomerular Capillary Hydrostatic Pressure

GCHP

A

The blood pressure in glomerular capillaries that promotes filtration by forcing water and solutes (in blood plasma) through the filtration membrane.

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54
Q

Bowman’s Space Colloid Osmotic Pressure

BSCOP

A

The presence of proteins in the Bowman’s space fluid that promotes filtration by attracting water molecules to the Bowman’s space.

The BSCOP is considered to be 0 mmHg under normal conditions since the Bowman’s space fluid has minimal protein.

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55
Q

Bowman’s Space Hydrostatic Pressure

BSHP

A

The pressure exerted against the filtration membrane by fluid within the Bowman’s space (and renal tubule) that opposes filtration (by creating a “back pressure” to inhibit water/solute filtration).

56
Q

Plasma Colloid Osmotic Pressure

PCOP

A

The presence of proteins in the glomerular capillary blood plasma that opposes filtration by attracting water molecules into the glomerular capillaries.

57
Q

Formula: Net Filtration Rate (NFP)

A

NEP = (PGC + πBS) – (PBS + πGC)

Net Filtration Rate = The total pressure that promotes glomerular filtration.

58
Q

Glomerular Filtration Rate

GFR

A

The total amount of filtrate formed in all renal corpuscles of the kidneys each minute.

59
Q

What may occur if the GFR is too high?

A

Physiologically important/needed substances may pass too quickly through the renal tubules (such that they are not reabsorbed) and be lost in the urine.

60
Q

What may occur in the GFR is too low?

A

Nearly all filtrate fluid may be reabsorbed (as the filtrate flows through the renal tubule), leading to inadequate excretion of waste products.

61
Q

Three Mechanisms of GFR Regulation

A
  • Renal Autoregulation
  • Hormonal Regulation
  • Neural Regulation
62
Q

Two Ways of Altering GFR

A
  • Adjust Blood Flow to Glomerular Capillaries
  • Adjust Available Glomerular Capillary Surface Area
63
Q

Renal Autoregulation

A

The ability of the kidneys to independently maintain a constant renal blood flow and GFR despite variations in systemic blood pressure.

64
Q

Two Mechanisms of Renal Autoregulation

A
  • Myogenic Mechanism
  • Tubuloglomerular Feedback
65
Q

Myogenic Mechanism

Renal Autoregulation

A
  • Elevated GFR (caused by elevated systemic blood pressure) increases the stretch of afferent arteriole walls, which trigger the arteriole smooth muscle fibers to contract to narrow the arteriole lumen (and reduce GFR).
  • Low GFR (caused by low systemic blood pressure) decreases the stretch of afferent arteriole walls, which trigger the arteriole smooth muscle fibers to relax to dilate the arteriole lumen (and increase GFR).

The myogenic mechanism actsvery quickly to normalize renal blood flow and GFR .

66
Q

Tubuloglomerular Feedback

A
  • Elevated GFR (caused by elevated systemic blood pressure) decreases the reabsorption of ions/water in the proximal tubule and Loop of Henle; Macula Densa cells (of the distal tubule) detect increased ion/water concentrations within the filtrate fluid and inhibit release of nitric oxide from JG cells (to decrease glomerular capillary blood flow).
  • Low GFR (caused by low systemic blood pressure) increases the reabsorption of ions/water in the proximal tubule and Loop of Henle; Macula Densa cells detect decreased ion/water concentrations within the filtrate fluid and promote release of nitric oxide from JG cells (to increase glomerular capillary blood flow).

The tubuloglomerular feedback mechanism acts slowly to normalize renal blood flow and GFR.

67
Q

Which two hormones contribute to GFR regulation?

A
  • Angiotensin II
  • Atrial Natriuretic Peptide (ANP)

  • Angiotensin II decreases GFR.
  • ANP increases GFR.
68
Q

Angiotensin II

A

A potent vasoconstrictor hormone that narrows both afferent arterioles and efferent arterioles to reduce renal flow (and decrease GFR).

69
Q

What stimulates the production of Angiotensin II?

A

Decreased Blood Pressure/Volume

70
Q

What proportion of the filtrate fluid is reabsorbed during tubular reabsorption?

A

99%

71
Q

Which portion of the nephron makes the largest contribution to tubular reabsorption?

A

Proximal Tubule

72
Q

Two Important Outcomes of Tubular Secretion

A
  • Blood pH Regulation via H+ Secretion
  • Secretion of Unneeded/Foreign Substances
73
Q

Two Routes of Tubular Reabsorption

A
  • Paracellular Route: Absorbed substances move between adjacent tubule cells.
  • Transcellular Route: Absorbed substances move through an individual tubule cell.
74
Q

Which capillaries receive the reabsorbed fluid/ions during tubular reabsorption?

A

Peritubular Capillaries

75
Q

Tubule Cell: Apical Membrane vs. Basolateral Membrane

A
  • Apical Membrane: Contact w/ Tubule Fluid
  • Basolateral Membrane: Contact w/ Interstitial Fluid
76
Q

Why is the concentration of Na+ low in renal tubule cells (and other cells of the body)?

A

The sodium-potassium pumps (Na+/K+ ATPases) of renal tubule cells eject Na+ ions into the extracellular environment.

77
Q

Why is it critical that Na+/K+ ATPases are located only within the tubule cell’s basolateral membrane?

A

Na+ ions can flow unidirectionally out of the tubule lumen (and into the interstitial fluid) during tubular reabsorption.

78
Q

Two Types of Water Reabsorption

Tubular Reabsorption

A
  • Obligatory Water Reabsorption
  • Facultative Water Reabsorption
79
Q

Obligatory Water Reabsorption

A

The reabsorption of water from the tubular fluid that accompanies the reabsorption of solutes (from the tubular fluid).

Obligatory water reabsorption occurs in the proximal tubule and Loop of Henle’s descending loop.

80
Q

Facultative Water Reabsorption

A

The reabsorption of water from the tubular fluid that is regulated by Antidiuretic Hormone (and is not facilitated by solute reabsorption).

Facultative water reabsorption occurs in the late distal tubule and collecting duct.

81
Q

Why does obligatory water reabsorption occur in the LOH’s descending limb, but not in the LOH’s ascending limb?

LOH = Loop of Henle

A
  • The LOH’s descending limb is permeable to water, so water can diffuse from the tubular fluid via osmosis (to follow solute reabsorption).
  • The LOH’s ascending limb is impermeable to water, so water reabsorption cannot accompany solute reabsorption at this site.
82
Q

Which portions of the nephron are always permeable to water?

A
  • Proximal Tubule
  • Loop of Henle’s Descending Limb
83
Q

What is the function of the microvilli on tubule cell apical membranes?

A

The microvilli increase the surface area available for tubular reabsorption and tubular secretion.

84
Q

What portion of the nephron reabsorps all organic nutrients?

Organic Nutrients = Glucose, Amino Acids, Vitamins

A

Proximal Tubule

85
Q

How does glucose reabsorption from the tubular fluid occur?

A
  • The Na+-Glucose Symporter carries Na+ and a glucose molecule from the tubular fluid (across the apical membrane) into the proximal tubule cell.
  • The glucose molecule exits the proximal tubule cell via facilitated diffusion (across the basolateral membrane) and diffuses into the peritubular capillary.
86
Q

In which tubule cell membrane are Na+ symporters located?

A

Apical Membrane

87
Q

How does amino acid reabsorption from the tubular fluid occur?

A
  • The Na+-Amino Acid Symporter carries Na+ and an amino acid from the tubular fluid (across the apical membrane) into the proximal tubule cell.
  • The amino acid exits the proximal tubule cell via facilitated diffusion (across the basolateral membrane) and diffuses into the peritubular capillary.
88
Q

Proportions: Reabsorption in Proximal Tubule

A
  • 100% = Organic Nutrients (Glucose, Amino Acids, Vitamins)
  • 80% = HCO3–
  • 65% = Water, Na+, K+, Ca2+
  • 50% = Cl–
89
Q

Proportions: Reabsorption in Loop of Henle

A
  • 35% = Cl–
  • 25% = Na+, K+, Ca2+
  • 15% = Water
  • 10% = HCO3–
90
Q

Why do cells lining the proximal tubule and LOH descending limb have particularly high permeability to water?

A

These cells posses many Aquaporin-1 molecules, so the rate of water movement across the apical/basolateral membranes is greatly enhanced.

91
Q

How do proximal tubule cells contribute to acid-base balance?

A
  • Secretion of H+ (via Na+/H+ Antiporters)
  • Reabsorption of HCO3–
92
Q

Which compounds are reabsorped in the proximal tubule?

A
  • Water
  • Glucose
  • Amino Acids
  • Na+
  • K+
  • Ca2+
  • Cl–
  • HCO3–
93
Q

Which compounds are secreted in the proximal tubule?

A
  • H+
  • Drugs
  • Nitrogenous Wastes
94
Q

Why is the tubular fluid of the LOH descending limb isoosmotic to blood?

A

The rates of water reabsorption and solute reabsorption remain roughly equal throughout the proximal tubule. (So, the osmolarity of tubular fluid entering the LOH is roughly equal to the osmolarity of blood entering the glomerulus.)

95
Q

Loop of Henle: Solute Permeability

A
  • Descending Limb: Impermeable to Solutes
  • Ascending Limb: Permeable to Solutes
96
Q

What is the result of the LOH descending limb being permeable to water and impermeable to solutes?

A

The tubular fluid (after passing through the LOH descending limb) becomes hyperosmotic to the blood.

Water reabsorption occurs in the LOH descending limb without any solute reabsorption.

97
Q

What is the result of the LOH ascending limb being permeable to solutes and impermeable to water?

A

The tubular fluid (after passing through the LOH ascending limb) becomes hypoosmotic to the blood.

Solute reabsorption occurs in the LOH ascending limb without any water reabsorption.

98
Q

Why is osmosis out of the tubular fluid able to occur in the LOH descending limb?

Tubular Reabsorption

A

An osmotic gradient exists in the renal medulla (directed toward the interstitial fluid) due to the buildup of ions/urea in the interstitial fluid.

  • The Loop of Henle extends into the renal medulla.
  • The buildup of ions/urea in the interstitial fluid results from reabsorption in the proximal tubule.
99
Q

What molecule permits the reabsorption of Na+ ions in the early distal tubule?

A

Na+/Cl– Symporter

The Na+/Cl– Symporter is located in the apical membrane of the early distal tubule cell.

100
Q

Principle Cells

A

The main cell type of the late distal tubule and collecting duct that reabsorps Na+ and secretes K+.

101
Q

What is unique about the amount of water/solute reabsorption and water/solute secretion that occurs in the the late distal tubule and collecting duct?

A

The amounts of reabsorption and secretion vary according to the body’s physiological needs.

102
Q

Antidiuretic Hormone (ADH)

Vasopressin

A

A hormone released by the Pituitary gland that stimulates facultative water reabsorption (from the filtrate fluid) by Principle Cells of the late distal tubule and collecting duct.

103
Q

Aldosterone

A

A steroid hormone produced by the adrenal cortex that promotes Na+ reabsorption (and thus water reabsorption) and K+ secretion by Principle Cells of the late distal tubule and collecting duct.

104
Q

How is Na+ transported/reabsorbed into the cells of the late distal tubule and collecting duct?

A

Facilitated Diffusion via Na+ Leak Channels

  • The Na+ Leak Channels are located in the apical membrane of the tubular/duct cells.
  • In all other portions of the nephron, Na+ reabsorption into the tubular cells occurs via Na+ symport/antiport.
105
Q

How does K+ secretion (into the tubule lumen) in the late distal tubule and collecting duct occur?

A

Na+/K– ATPases in the basolateral membrane of the tubule cells maintain a high intracellular K+ concentration, so K+ ions can diffuse into the tubule lumen (via K+ Leak Channels).

106
Q

How does ADH increase facultative water reabsorption throughout the late distal tubule and collecting duct?

A

ADH increases the water permeability of the Principle cells by stimulating the insertion (via exocytosis) of Aquaporin-2 channels within the cells’ apical membranes.

107
Q

Why do Principle cells (of the late distal tubule and collecting duct) have low permeability to water?

A

The Principle cells possess a higher-than-normal level of cholesterol within their apical membranes.

108
Q

What effect does ADH release have on the blood?

Hormonal Regulation of Tubular Reabsorption/Secretion

A
  • Increased Blood Volume
  • Increased Blood Pressure
109
Q

How does ADH increase systemic blood pressure?

A

ADH increases the reabsorption of water in the late distal tubule and collecting duct (via Principle cells), which results in greater water flow out of the Principle cells and into the bloodstream.

110
Q

What stimulis lead to increases in ADH release?

A
  • Elevated Osmolarity of (Blood Plasma + Interstitial Fluid)
  • Decreased Blood Volume
111
Q

Which cells detect the osmolarity changes of blood plasma (and interstitial fluid)?

A

Osmosensitive neurons (via their osmoreceptors) in the Hypothalamus detect osmolarity deviances by sensing changes in their membrane potential.

112
Q

Renin

A

An enzyme released (into the bloodstream) by JG cells in response to decreased stretch in the afferent arteriole walls; it converts Angiotensinogen into Angiotensin I to initiate a pathway that increases blood volume and blood pressure.

  • JG Cells = Juxtaglomerular Cells (Afferent Arteriole)
  • Angiotensin I is eventually converted into Angiotensin II, which functions to decrease GFR and increase blood pressure.
113
Q

Angiotensinogen

A

An immature plasma protein synthesized in the liver that is converted into Angiotensin I by Renin.

114
Q

Angiotensin I

A

An inactive hormone formed from Angiotensinogen that is converted into Angiotensin II by ACE.

115
Q

Angiotensin II

A

An active-form hormone that decreases GFR (via vasoconstriction of afferent/efferent arterioles) and stimulates aldosterone release (to increase blood volume/pressure)

116
Q

Angiotensin-Converting Enzyme

ACE

A

The enzyme that converts Angiotensin I (inactive) to Angiotensin II (active).

117
Q

Two Effects of Angiotensin II

A
  • Decreased GFR: The vasoconstriction of afferent/efferent arterioles results in less plasma fluid loss during glomerular filtration (to maintain blood pressure levels).
  • Aldosterone Release: Secretion of aldosterone from the adrenal gland increases tubular reabsorption of Na+/water (to increase blood pressure).
118
Q

How does an increase in facultative reabsorption of water impact the blood?

A
  • Decreased Blood Osmolarity
  • Increased Blood Volume/Pressure
119
Q

Main Components of the Gastrointestinal Tract

A
  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine (Colon)
120
Q

Which components of the GI Tract possess stratified squamous epithelial tissue?

A
  • Mouth
  • Esophagus
  • Anus
121
Q

What purpose does stratified squamous epithelial tissue serve in certain portions of the GI Tract?

A

The mulilayered structure of stratified epithelial tissues helps to prevent abrasion-induced physical damage to underlying cells.

122
Q

What purpose does the musosal layer of the GI Tract serve?

A

Mucosal layer epithelial cells secrete mucus to protect GI tract tissues from digestion/damage by stomach acid (and digestive proteins).

123
Q

What purpose does the submucosal layer of the GI Tract serve?

A

Submucosal layer elastic connective tissue imparts flexibility to the GI Tract to enable stretching during the passage of food/chyme (and to accomodate compression during smooth muscle contraction).

124
Q

What purpose does the muscularis layer of the GI Tract serve?

A

Muscarlis layer muscular tissue can contract to churn food/chyme and push food/chyme through the GI Tract.

125
Q

Six Steps of Digestion

A
  • Ingestion (Mouth)
  • Propulsion (Esophagus)
  • Mechanical Breakdown (Mouth → Small Intestine)
  • Chemical Digestion (Mouth → Large Intestine)
  • Absorption (Small Intestine→ Large Intestine)
  • Defecation (Large Intestine)
126
Q

Examples: Mechanical Breakdown of Food

A
  • Chewing
  • Churning (Stomach)
127
Q

Examples: Chemical Breakdown of Food

A
  • Mouth: Salivary Enzymes (Amylase, Lipase, Lysozyme)
  • Stomach: Acid + Pepsin
  • Small Intestine: Pancreatic Enzymes (Peptidase) + Bile
  • Large Intestine: Bacterial Fermentation
128
Q

Pepsin vs. Pepsinogen

A

Pepsin: The protein’s active form created by the self-cleavage of Pepsinogen within the acidic stomach environment.
Pepsinogen: The protein’s inactive form secreted by the Chief cells of the stomch.

Pepsin = Protease

129
Q

Where in the GI tract does most digestion occur?

A

Small Intestine

130
Q

Trypsin

A

A protease enzyme (yielded from Trypsinogen) that initiates digestion of proteins in the small intestine by cleaving long chains of amino acids.

131
Q

What unique chemical characteristic of Bile Salts enables them to aid lipid digestion?

A

Amphipathicity

Amphipathic molecules contain nonpolar regions and polar regions.

132
Q

Bile

A

A substance secreted by the liver (and stored in the Gallbladder) that functions to emulsify lipids prior to their digestion.

Bile consists of water, bile salts, cholesterol, and ions (and bile pigments and lecithin).

133
Q

What functions due beneficial/mutualistic bacteria of the GI tract serve?

A
  • Additional Digestion: Digest foods/nutrients that cannot be decomposed by the human’s GI organs.
  • Protection: Prevents harmful/parasitic bacteria from colonizing the gut (and causing disease).
  • Metabolite Production: Produces metabolic byproducts (e.g. SCFAs, Vitamins) that can be absorbed in the large intestine.
134
Q

Symptoms: Clostridium difficile Toxin

A
  • Diarrhea
  • GI Tissue Damage
135
Q

Treatment: Clostridium difficile Infection

A
  • Antibiotics (Primary)
  • Fecal Transplant (Secondary)
136
Q

Where in the GI tract does most absorption occur?

A

Small Intestine

137
Q

How does gluten ingestion impact the small intestine of Celiac patients?

A

Atrophied Villi: The cells of the small intestine possess less lumen-facing surface area, which decreases the capacity for digestion/absorption of nutrients.

Human Physiology (5 decks)

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