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UA / Biology / BSC 216 / How long does each stage of digestion take?

How long does each stage of digestion take?

How long does each stage of digestion take?


School: University of Alabama - Tuscaloosa
Department: Biology
Course: Human Anatomy & Physiology II
Professor: Austin hicks
Term: Fall 2016
Cost: 50
Name: Exam 3 study guide (all but fluid, elec. acid/base)
Description: This is the first portion of the exam 3 study guide .
Uploaded: 11/12/2017
21 Pages 47 Views 6 Unlocks


How long does each stage of digestion take?


∙ Five stages of digestion:

1. Ingestion

2. Secretion

3. Propulsion

4. Digestion

5. Absorption

6. Defecation

∙ Mechanical digestion: physical breakdown

-cutting and grinding of teeth

-churning of stomach and intestines

∙ Chemical digestion: series of hydrolysis reactions that breaks  dietary macromolecules into their monomers  

-carried out by digestive enyzymes

 ∙     digestive tract 




What is mechanical breakdown in the digestive system?


small intestine

large intestine  

 ∙     accessory organs 



salivary glands




∙ wall of digestive tract (inner to outer) 



muscularis externa


∙ enteric nervous system 

-monitors tension in gut wall and conditions in lumen

-made up of 2 neuron networks

1. submucosal plexus-controls glandular secretion of  

mucosa/movements of muscularis mucosae

What does the enteric nervous system control?

2. myenteric plexus (muscularis interna)-peristalsis and  contractionos of muscularis externa

∙ mesenteries: suspend the stomach and intestines from  abdominal wall

-allow for intestinal and stomach contractions  We also discuss several other topics like What is an aniconic phase?

-allow free movement in cavity

-hold abdominal viscera in place

-prevent twisting of intestines

-provides blood vessel/nerve passage through tract

-holds lymph nodes and vessels

∙ neural, hormonal, and paracrine mechanism control 

-control motility and secretion


short reflexes: stretch or chemical stimulation acts  


long reflexes: motility and secretion


chemical messengers secreted into bloodstream (gastrin  

and secretin)


chemical messengers that diffuse through tissues

expected learning outcomes:

∙ Discuss the structure and basic functions of the oral cavity, the  different types of teeth, and the tongue We also discuss several other topics like Does temperature affect concentration in equilibrium?

-oral cavity starting point for digestive system (ingestion,  

secretion, chemical and mechanical digestion, propulsion all  occur in cavity) We also discuss several other topics like What is important in the absorptive state?

-oral cavity+ accessory organs turn ingested food into bolus and  move it to posterior portion of cavity to be swallowed If you want to learn more check out What is the capital of utah?

-mastication (chewing)-food stimulates oral receptors that trigger and involuntary chewing reflex

-teeth are key organs of mechanical digestion  

-incisors: central teeth-narrow crown, broad and flat-used for  cutting pieces of food

-canines: on either side of incisors-pointed crowns-specialized for ripping and tearing

-molars: posterior and lateral to canines-broad crowns

specialized for grinding

∙ Describe the structure and function of the salivary glands, their  respective ducts, and the products secreted by their cells.  -moisten mouth  

-begin starch and fat digestion

-cleanse teeth

-inhibit bacterial growth

-dissolve molecules for taste bud stimulation

-moisten food into bolus to aid in swallowing

-intrinsic salivary glands-dispersed amid other oral tissues If you want to learn more check out What does it mean to be evolutionarily fit?

lingual (tongue)

labial (lips)

buccal (cheek)

-extrinsic salivary glands-connected to oral cavity via ducts parotid-anterior to the earlobe

submandibular gland- halfway along mandible body

sublingual-floor of mouth

-cells of acini-fliter blood-add amylase, mucin, and lysozyme -salivary nuclei-respond to signals generated by food

parasympathetic-thin, enzyme rich saliva

sympathetic stimulation-thick, saliva with more mucous

∙ Describe and classify the regions of the pharynx with respect to  passage of food and/or air through them.  

-pharyngeal constrictors-inferior, middle, superior-force food  downward during swallowing

-inferior constrictor stays constricted when not swallowing to  exclude air from esophagus (upper esophageal sphincter) We also discuss several other topics like Who signed the clean water act to “prevent, monitor & penalize” industrial activity that would be harmful to the us water supply?

-becomes physiological sphincter when relaxed

∙ Describe the structure and function of the esophagus, including  the locations of skeletal and smooth muscle within its wall.  -muscular tube-begins at C6

-extends from pharynx to cardiac orifice of stomach

-lower esophageal sphincter-prevents stomach contents from  regurgitating into


-protects esophageal mucosa from  

erosive effect of

stomach acid

∙ Explain the process of deglutition, including the changes in  position of the glottis and larynx.  


-swallowing center coordinates swallowing (nuclei in medulla  oblongata)

1. voluntary phase

-tongue collects food and it is pressed against palate and bolus  forms

-food collects in front of epiglottis-bolus slides through laryngeal  opening

-tactile receptors stimulated when bolus enters laryngeopharynx  which activates next phase

2. pharyngeal phase-involuntary

-food prevented from reentering mouth/nasal cavity or larynx via  tongue, soft palate and epiglottis

-bolus driven downward via pharyngeal contrictors

3. esophageal phase

-bolus enters esophagus and peristalsis is triggered-moves down  to stomach

-peristalsis-waves of muscular contractions the push bolus  (involuntary)

-ensures you can swallow regardless of body position

∙ Describe the structure and function of the different regions of the  stomach 

-muscular sac in upper left abdominal cavity immediately inferior to  diaphragm  

-functions as food storage open

-breaks up food particles

-liquifies food-chyme: semidigested food in stomach (soupy) -begins chemical digestion of protein and fat-most digestion occurs  after chyme passes on to SI

∙ Describe the structure of the gastric glands and the functions of the  types of cells they contain.  

-gastric pits are depressions in gastric mucosa-simple columnar  epithelium

-cardiac glands

-pyloric glands

-gastric glands-rest of stomach

-mucous cells: secrete mucus

-regenerative (stem) cells: produce a continual supply of new cells to  replace cells that die  

-parietal cells: secrete HCl, intrinsic factor and a hunger hormone -chief cells: secrete gastric lipase and pepsinogen

-enterendocrine cells: secrete hormones and paracrine messengers  that regulate digestion

-produce gastric juice-contains water, HCl, and pepsin

∙ Discuss the function, production, and regulation of the secretion of  hydrochloric acid.  

-component of gastric juice

-one of the main secretions of gastric glands

-parietal cells produce HCl

-H+ pumped into gastric gland lumen by H ATP pump

-chloride ion pumped into the lumen of gastric gland to join H+  forming HCl

-activates pepsin and lingual lipase

-breaks up connective tissues and plant cell walls-liquefies food to form chyme

-converts ferric ions to ferrous ions-hemoglobin synthesis -contributes to nonspecific disease resistance by destroying ingested  pathogens

∙ Pepsin-digests dietary proteins into shorter peptide chains -pepsinogen (digestive enzyme-inactivates) converted into activate  pepsin via HCl and autocatalytic effect

∙ Gastric lipase-plays a minor role in digesting dietary fats (10-15%) ∙ Intrinsic factor-glycoprotein secreted by parietal cells -essential to B12 absorption-needed to synthesize hemoglobin -only indispensable function of stomach (B12 supplementsrequired for  digestion if stomach is removed

∙ Chemical messengers-produced by gastric and pyloric glands -most are hormones

-some are paracrine secretions

-peptides (gut-brain peptides)

∙ Receptive-relaxation response: stomach resists stretching briefly, but  relaxes to hold more food

∙ Stomach shows rhythm of peristaltic contractions controlled by  pacemaker cells-mixes food with gastric juice-churns and promotes  physical breakup and chemical digestion

∙ Duodenum neutralizes stomach acid by digesting nutrients little by  little

∙ Most digestion and nearly all absorption occur after chyme has passed  into SI

∙ Stomach protected from acidic and enzymatic environment in 3 ways 1. Mucous coat

2. Tight junctions

3. Epithelial cell replacement  

∙ Explain the effects of the cephalic, gastric, and intestinal phases on the functions of the stomach and small intestine.  

-cephalic phase-stomach controlled by brain

-stomach responds to sense of food

-enteric nervous system of stomach stimulated-gastric secretion -gastric phase-stomach controls itself

-2/3 of gastric secretion occurs

-ingested food stretches stomach and increases pH contents -stimulated by 3 chemicals:

1. acetylcholine-parasympathetic nerve fibers

2. histamine-paracrine secretion from enterendocrine cells 3. gastrin-produced by enterendocrine cells in pyloric glands -intestinal phase-stomach controlled by SI

-duodenum responds to arrival of chyme and moderates gastric  activity through

hormones and nervous reflexes

-both enhances and inhibits gastric secretion


-stretching of duodenum leads to stimulation of stomach  -peptides and amino acids in chyme stimulate G cells of  duodenum to secrete

gastrin which stimulates stomach more


-enterogastric reflex-duodenum sends inhibitory signals to  stomach via this

 nervous system

-chyme stimulates duodenal enteroendocrine cells to release  secretin and cholecytostokinin- suppress gastric secretion ∙ Describe the gross and microscopic structure of the pancreas and its  digestive functions. -endocrine portion-islets (secrete insulin and  glucagon)

-exocrine portions-99% of the pancreas

-secretory acini-secrete into small ducts

-acini-secrete enzymes and zymogens

-ducts-secrete bicarbonate

-pancreatic ducts-runs lengthwise through middle of gland -joins bile duct at hepatopancreatic ampulla

-accessory pancreatic duct-branches from main duct

-opens into duodenum independently  

pancreatic zymogens 





-pancreatic amylase

-pancreatic lipase


∙ Describe the gross and microscopic structures of the liver and  gallbladder.  

-liver: reddish brown

-located inferior to diaphragm

-largest gland in the body

-secretes bile

-gallbladder: pear shaped sac on underside of liver

-stores and concentrates bile

-bile: fluid containing minerals, cholesterol, fats, phospholipids, bile  pigments and acids

-bilirubin: derived from decomposition of hemoglobin  

-bile acids: steroids synthesized from cholesterol-aid in fat digestion

-80% of bile acids are reabsorbed and returned to liver

-20% are excreted as feces-elimination of excess cholesterol

∙ Describe the functions of the liver pertaining to digestion.  

-absorb nutrients from blood for metabolism or storage (hepatocytes)  after meal

-remove and degrade (toxins and drugs)

-secrete albumin, lipoproteins, clotting factors, angiotensinogen into  blood

-break down stored glycogen and release glucose into blood between  meals

∙ Explain the structural and functional relationship between the liver and the gallbladder. -gallbladder on underside of liver

-bile secreted by liver and fills the bile duct and overflows into  gallbladder

-if bile acids reabsorbed after leaving gallbladder, they return to liver  (80%)

∙ Explain how pancreatic and biliary secretions are regulated.  -Acetylcholine

-Stimulates acini to secrete their enzymes during the cephalic  phase of gastric control even before food is swallowed


-Secreted by mucosa of duodenum in response to arrival of fats in  small intestine  

 -Stimulates pancreatic acini to secrete enzymes

 -Strongly stimulates gallbladder  

 -Induces contractions of the gallbladder and relaxation of hepatopancreatic  sphincter causing discharge of bile into the duodenum


 -released from duodenum in response to acidic chyme arriving from  the stomach  

-Stimulates ducts of both liver and pancreas to secrete more sodium  bicarbonate (buffering action)

-Raising pH to level pancreatic and intestinal digestive enzymes  require  

∙ Describe the structure and functions of the duodenum, jejunum, and  ileum. 


-begins at pyloric valve

-Receives stomach contents, pancreatic juice, and bile

-Stomach acid is neutralized here


-most digestion and absorption occurs here


-peyer’s patches-surveillance of pathogens in SI

∙ Discuss the histology and functions of the circular folds, villi, and  microvilli of the small intestine.  

-large SA is for effective digestion and absorption

-circular folds:  

-increase surface area by factor of 2 or 3

-largest folds

-only have mucosa and submucosa

 -Occur from the duodenum to the middle of the ileum

1 -Cause chyme flow in spiral path causing more contact with  mucosa  

 -Promotes more thorough mixing and nutrient  absorption  


-make mucosa look fuzzy

-covered with 2 types of epithelial cells (absorptive and goblet) -tight junctions join epithelia and prevent digestive enzymes  from seeping



-border on apical surface of each absorptive cell

-brush border enzymes: in plasma membrane (carry out final  digestion stages)

∙ Describe the functions and regulation of motility in the small intestine. Contractions:

-mix chyme with intestinal juice, bile, and pancreatic juice -neutralize acid/digest nutrients more effectively  

-churn chyme and bring it in contact with mucosa for contact digestion  and nutrient absorption  

-move residue toward LI

-segmentation-stationary ringlike constrictions along intestine -rhythm set by pacemaker cells

-mix and churn

-peristalsis-wavelike movement of contents toward colon -begin in duodenum  

-milk chyme towards colon over a 2 hour perio

∙ Describe the locations of carbohydrate, protein, fat, and nucleic acid  digestion. Name the enzymes involved in the digestion process.

Carbohydrate-mouth (salivary amylase)small intestine(pancreatic  amylase)(brush border enzymes)

Protein-stomach (pepsin) small intestine (trypsin, chymotrypsin,  carboxypeptidase)(brush border enzymes)

Fat-small intestine (bile salts)(pancreatic lipase)

Nucleic acids-small intestine (pancreatic RNA and DNA)(brush border  enzymes)

∙ Describe how each of the above is absorbed by the small intestine.  Carbohydrate

-monosaccharides (glucose and galactose) are absorbed via  cotransport with

sodium ions; fructose passes via facilitated diffusion.

-monosaccharides enter capillary blood in the villi and are  transported to the

liver via hepatic portal vein


-amino acids absorbed via cotransport with sodium ions; enter  capillary blood in

villi and are transported to liver via hepatic portal vein


-fatty acids and monoglycrides enter intestinal cells via diffusion; combined with

proteins within cells, and resulting chylomicrons are extruded. -enter the lacteals of the villi and transported to systemic  circulation via the

lymph in the thoracic duct.

-glycerol and short chain fatty acids are absorbed into the  capillary blood in the

villi and transported to the liver via the hepatic portal vein Nucleic acid

-active transport via membrane carriers

-absorbed into capillary blood in the villi and transported to the  liver via the

hepatic portal vein

∙ Describe the gross and microscopic anatomy of the divisions of the  large intestine.  

-measures 5 ft long and 2.5 in in diameter

-eliminates feces by defecation  

-ascending, transverse, descending, sigmoid  

∙ Describe the defecation reflex and the functions of the internal and  external anal sphincters.  

-defecation reflex contraction of rectum initiates defecation -internal/external anal sphincters relax to stimulate defecation


∙ Calorie (capital C): unit of calorie used to measure human diet  

∙ Define the terms metabolism, catabolism, and anabolism.  -metabolism: sum of the body’s chemical reactions that consists of a  series of enzyme-catalyzed reactions called metabolic pathways  -cataboism: breakdown of large molecule into a smaller one-releases  energy

-anabolism: synthesis of large molecules by combining smaller  monomers-requires energy

∙ Identify the nutrients the body is able to use for fuel.  

-glucose: dietary carbs and those stored by the body are typically  degraded to the monosaccharide glucose-preferred brain and liver cell  fuel

-fatty acids: lipids broken down into free fatty acids and glycerol -amino acids: individual amino acids separated out to be converted  into fuel  

∙ Compare and contrast endergonic and exergonic reactions.  -Exergonic: release energy resulting in products with less energy than  the original reactants possessed (catabolic)

-endergonic: require input of energy to proceed. Products possess more energy than reactants (anabolic)

∙ Describe the process of phosphorylation.  

-energy harnessed from ATP drives cellular processes 2 ways: -used by cell directly for fuel

-used for phosphorylation: process where ATP donates a phosphate  group to a reactant under direction of an enzyme-leads to reactant  becoming more reactive, favoring conversion into product  

∙ Describe the hydrolysis of ATP, and explain why this reaction in  exergonic.  

-3rd phosphate group is removed

-energy released-40% harnessed for work-60% lost as heat  -great deal of energy released when 2nd and 3rd phosphate bond is  broken=exergonic  

∙ Explain what happens in an oxidation-reduction reaction and how  electrons are transferred between reactants, including NADH and  FADH2. 

-electrons transferred from one molecule to another when fuel is  burned

-releases energy and heat

-loses electrons=oxidized

-gains electrons=reduced  

-electron carriers accept electrons that are removed from oxidation of  nutrient molecules

-NAD and FAD are electron carriers that accept electrons from nutrient  molecules

-eventually transfer their electrons to other carriers (NADH and  FADH2)

∙ Explain the overall reaction for glucose catabolism.  

-reactions that involve the breakdown of carbohydrates into glucose -use chemical energy in glucose to drive ATP synthesis

-glycolysis and citric acid cycle are two main components that  generate ATP

∙ Describe the processes of glycolysis, formation of acetyl CoA, and the  citric acid cycle.  

-glycolysis: breakdown of glucose in a series of 10 enzymatic reactions  -occurs in cytosol  

-glucose 2 pyruvate molecules

-energy investment phase-part of the 10 reactions

1. first phosphorylation: glucose phosphorylated by ATP, yields  glucose-6

phosphate and ATP

2. second phosphorylation: carbon atoms in glucose-6-phosphate rearranged

and phosphorylated by another ATP; yields fructose-1,6- biphosphate and ADP

3. cleavage: fructose-1,6-biphosphate split into 2 3-Carbon  molecules (ready to

enter payoff phase)

-energy payoff phase-five remaining reactions condensed into 2 steps  -phosphate groups of 3-carbon sugars are transferred to ADP to  yield

ATPoxidized to produce NADH

1. oxidation: glyceraldehyde-3-phosphate is phosphorylated and  oxidized by NAD+ to yield NADH and 1,3-biphosphoglycerate  (donates P to ADPATP)

2. ATP synthesis: carbon atoms in 3-phosphoglycerate  

rearranged to form phophoenol pyruvate (donates P to  

ADPATP and pyruvate)

-acteyl CoA made under aerobic conditions-when oxygen is available  following glycolysis

-pyruvate moves into mitochondria and loses a carbon atom to  yield acetate and


-acetate oxidized by NAD+ and linked to CoA to make acetyl  CoAenters citric

acid cycle

-citric acid cycle: 

-8 reactions that make up second part of glucose metabolism  1. citrate synthesis: acetyl-CoA combines with oxaloacetate to form  citrate and CoA

2. first oxidation: citrate is rearranged, then oxidized by NAD+  generating CO2 and NADH

3. ATP synthesis: succinyl-CoA is converted to succinate and CoA while  forming ATP

4. second oxidation: succinate is oxidized by FAD and NAD+ generating FADH2 and NADH, and is converted back to oxaloacetate

∙ Discuss the process of the electron transport chain.  

-involves transfer of electrons during oxidative phosphorylation  process-leads to ATP synthesis

-final stage

-reduced electron carriers from glycolysis and citric acid cycle feed into ETC and participate in oxidative phosphorylation and 3 interrelated  processes

1. oxidative phosphorylation: series of oxidation-reduction reactions  that allow cells to use energy for a process that yields ATP  -NADH and FADH2 are oxidized

-force created by those is used in Complex I to pump H ions into  intermembrane


-continued electron flow in complexes III and IV drive H ions into  intermembrane


-complex IV transfers electrons to oxygen to form H2O

2. transfer of electrons between electron carriers

-more than 15 electron carriers make up the ETC

-electrons move down the chain between carriers to form H+  atoms

3. generation and maintenance of a hydrogen ion gradient -hydrogen ions are pumped into intermembrane space and this  creates a  


4. use of hydrogen ion gradient to drive ATP synthesis

-flow of hydrogen ions through an ATP synthase rotor causes it to spin and with

the enzyme that catalyzes ATP, ATP is released  

∙ Discuss the process of chemiosmosis and its role in ATPproduction.

-potential energy becomes kinetic energy that drives ATP synthesis as  the H ions flow through and ion channel across the inner membrane

∙ Give the energy yield of glucose catabolism  

-10 NADH molecules (2 from glycolysis, 2 from pyruvate ox., 6 from  citric acid cycle)

-2 FADH2 molecules

-4 ATP molecules (2 from glycolysis, 2 from citric acid cycle)

-when one molecule of glucose is completely oxidized, energy gain=38 ATP

∙ Describe lipolysis, deamination, and transamination.  -lipolysis: enzyme catalyzed process that liberates fatty acids and  glycerol

-both used for energy generation (glycerolglyceraldehyde-3- phosphate; enters glycolysis)(fatty acids catabolized to acetyl CoA by beta oxidation)

-most energy in triglycerides derived from fatty acid beta  oxidation

-transamination: amino group is removed and transferred to alpha ketoglutarate during amino acid catabolism

-deamination: produces ammonia and alpha-ketoglutarate ∙ Summarize the beta-oxidation of fatty acids, and explain how it leads  to ATP production and relates to ketogenesis.  

-beta oxidation: fatty acids enter the mitochondrial matrix of cells that  can oxidize them (skeletal and cardiac)

 – Each fatty acid is bound to coenzyme A and  initiates a series of reactions called

1 beta-oxidation  

– Fatty acid chain is oxidized and has two carbons removed • Produces NADH,FADH2, acetyl-CoA, and a shorter fatty  acid with two

fewer carbons

-NADH and FADH2 proceed to ETC

-acetyl-CoA enters citric acid cycle

-ketone bodies generated by break down of fatty acids and can be  used by cardiac and skeletal cells

∙ Explain how amino acid catabolism leads to ATP production.  -dietary proteins broken down into amino acid subunits that can be  used for catabolism

-transamination removes amino group and leaves a carbon skeleton  that is converted and then oxidized for energy and glutamate. -oxidative deamination

-produces ammonia and alpha-keotglutarate

-some amino groups removed are used to synthesize new amino  acids

-remaining ammonia removed by urea cycle

∙ Describe the effect of amino acid catabolism on ammonia and urea  production  

-remaining ammonia molecules from oxidative deamination are  removed via the urea cycle

-urea is formed by combo of 2 ammonia molecules and CO2  -eliminated by the kidneys in the urine  

∙ Describe the processes of glycogenesis, glycogenolysis, and  gluconeogenesis.  

-glycogenesis: storage of excess glucose obtained from diet -synthesis of glycogen via a series of enzyme catalyzed reactions -add glucose units to growing storage molecule

-glycogenolysis: catabolic process that cleaves glucose units off of  glycogen to maintain blood glucose homeostasis

-gluconeogenesis: mechanism by which glucose is synthesis from  noncarbohydrate molecules

-kicks in once glycogen supplies have been exhausted  

-hepatocytes and specific kidney cells convert 3-and 4-carbon  compounds into glucose

∙ Describe the process by which fatty acids are synthesized and stored  as triglycerides in adipose tissue.  

-resembles beta-oxidation in reverse  

-lipogensis is used to synthesize fatty acids  

-fatty acid synthase catalyzes a reaction that progressively lengthens  fatty acid chains two carbon units at a time  

-most fatty acids are attached to glycerol and assembled into  triglycerides in the ER and stored in adipocytes

-majority of energy stored as triglycerides in adipose tissue  

∙ Explain how nutrients may be converted to amino acids and lipids if  needed.  

-body synthesizes 11/20 amino acids

-amino group added to a carbon skeleton molecule (alpha ketoglutarate, pyruvate, oxalacatate)

∙ Explain the fate of excess dietary proteins and carbohydrates.  -excess amino acids converted to storage molecules

-glucogenic amino acids converted into glucose by glucogenesis  and stored as


-others converted to fatty acids and stored in adipose tissue  

∙ Compare and contrast the processes that occur in the absorptive and  postabsorptive states.  

-absorptive state:occurs immediately after feeding, from time ingested  nutrients enter blood

-oxidation of nutrient molecules (primarily glucose) to provide  fuel to cells

-glycogenesis: stores excess glucose in skeletal muscle and  hepatocytes

-lipogensis: stores triglycerides in adipocytes and hepatocytes -protein synthesis

-postabsorptive state: begins once nutrient absorption is complete  -occurs during late morning, late afternoon, and most of night -breakdown of proteins in muscle cells releases glucogenic amino acids into the


-ketogenesis in hepatocytes converts fatty acids to ketone bodies and releases

them into the blood

-glucogenesis and glycogenolysis in hepatocytes release glucose  into the blood

-lipolysis in adipocytes releases fatty acids into the blood -oxidation of molecules such as fatty acids provide most cells  with fuel

∙ Explain the roles on insulin and glucagon in the absorptive and  postabsorptive states.  

-the absorptive state is triggered by the release of insulin in response  to increased blood glucose levels

-glucagon is released when the blood glucose levels drop and triggers  glycogenolysis and glucogensis aka the postabsorptive state

∙ Describe the role of the hormones insulin and glucagon in regulating  glucose and amino acid catabolism and anabolism.  

-insulin lowers blood glucose levels after eating-happens during amino  acid anabolism

-glucagon raises blood glucose levels after the absorptive state has  ended-happens during amino acid catabolism

∙ Explain the significance of glycose sparing for neural tissue in the  postabsorptive state.  

-cells catabolize newly delivered fatty acids preferentially  -conserves glucose for cells of the nervous system

-non-nervous system cells can also use ketone bodies and amino acids  for fuel  

∙ Describe how feeding behaviors are regulated.  

-controlled by hormonal and neural signals that stimulate or inhibit  feelings of hunger

-satiety centerinhibits desire to eat (stimulated by leptin and  insulin)

-hunger centerstimulates desire to eat (stimulated by ghrelin) -feeding strectches stomach wall which releases gastrointestinal  hormones that stimulate the vagus nerve to indirectly suppress the  hunger center

-levels of molecules in blood stimulate or inhibit hypothalamic centers  that control certain feelings  


∙ List and describe the organs of the urinary system.  

-kidneys: filter fluid from the bloodstream to remove metabolic wastes  and toxins and return vital ions and water to the blood

-urinary bladder: storage reservoir

-ureters: transport urine

-urethra: transport urine  

∙ Describe the major functions of the kidneys.  

-removal of metabolic wastes

-regulation of fluid and electrolyte balance

-regulation of acid-base balance

-maintenance of blood pressure

-regulation of erythropoiesis

-performance of other metabolic functions

∙ Describe the external structure of the kidney, including its location,  support structures, and covering.  

-located between the dorsal body wall and the parietal peritoneum -fat capsule: attached kidney to body wall

-renal capsule: hard-protects against infection

-fascia: dense connective tissue-anchors kidney in place  

-renal pelvis-inner most portion-renal medulla (renal pyramids and  renal columns)-renal cortex-renal capsule-outermost portion

∙ Trace the path of blood flow through the kidneys.  

-renal arterysegmental arteryinterlobar arteryarcurate  arteryinterlobular arteryafferent arterioleglomerulusefferent  arterioleperitubular capillaries interlobular veinarcuate

veininterlobular veinrenal veininferior vena cavaheartaorta  

∙ Identify the major structures and subdivisions of the renal corpuscle,  renal tubules, and renal capillaries.  

-renal corpuscle: filters the blood plasma

-glomerular capsule

-renal tubules

-four regions

1. proximal convoluted tubule

2. nephron loop

3. distal convoluted tubule

4. collecting duct

∙ Describe the histological structure of the proximal tubule, nephron  loop, distal tubule, and collecting system, and trace the pathway of  filtrate flow through these tubules. 

-structures can be seen in figures

-glomerular capsule → proximal convoluted tubule → nephron loop →  distal convoluted tubule → collecting duct→ papillary duct → minor  calyx → major calyx → renal pelvis → ureter → urinary bladder →  urethra  

∙ Compare and contrast juxtamedullary and cortical nephrons.  -cortical nephrons

-85% of all nephrons

-short nephron loops

-efferent arterioles branch into peritubular capillaries around PCT and DCT

-juxtamedullary nephrons

-15% of all nephrons

-very long nephron loops

-maintain salinity gradient in the medulla and helps conserve  water

-efferent arterioles branch into vasa recta around long nephron  loop

∙ Describe the structure of the filtration membrane.  

-filtration membrane: three barriers through which fluid passes-allows  passage of water and small solutes into glomerular capsule  1. fenestrated endothelium of glomerular capillaries  


2. basement membrane

-albumin repelled by negative charge

3. filtration slits

-podocyte cell extensions wrap around capillaries to form a

barrier layer with

filtration slits

-negatively charged which is an additional obstacle from large  anions

∙ Define the glomerular filtration rate (GFR) and state its average  value.  

-glomerular filtration: special case of the capillary fluid exchange  process in which water and some solutes in the blood plasma pass  from the capillaries of the glomerulus into the capsular space of the  nephron

-GFR: amount of filtrate formed per minute by the two kidneys  combined  

-125mL/min male

-105 mL/min female  

∙ Describe the hydrostatic and colloid osmotic forces that favor and  oppose filtration.  

-glomerular hydrostatic pressure (BHP)

-primary means of pushing solutes and water out of blood, across filtration


-capsular hydrostatic pressure (CHP)

-pressure within capsule tends to push water back in to  


-glomerular colloid osmotic pressure (GCOP)

-proteins in glomerular blood tend to pull water back into  


∙ Predict specific factors that will increase or decrease GFR.  -increase:  

-fluid flows through the renal tubules too rapidly for them to  reabsorb the usual amount of water and solutes


-water is reabsorbed

∙ Describe the myogenic and tubular feedback mechanisms.  -renal autoregulation: ability of the nephrons to adjust their own blood  flow and GFR without external control  

-2 methods:

-myogenic mechanism: based on tendency of smooth muscle to  contract when


-increased arterial blood pressure stretches the afferent  

arteriole arteriole

constricts and prevents blood flow into the glomerulus from  changing much  

-blood pressure fallsafferent arteriole relaxes and allows blood  flow more

easily into glomerulus  

2 -tubuloglomerular feedback: glomerulus receives feedback on  the status of the downstream tubular fluid and adjusts filtration  to regulate the composition of the fluid, stabilize its own  performance, and compensate for fluctuation in systemic blood  pressure  

∙ Describe how and where water, organic compounds, and ions are  reabsorbed in the nephron by both passive and active processes.  -tubular reabsorption: process of reclaiming water and solutes from the tubular fluid and returning them to the blood

-transcellular route: substances pass through the cytoplasm of  the PCT epithelial

cells and out their base

-paracellular route: substances pass between PCT cells

 -water carries a variety of dissolved solutes with it via  solvent drag

-potassium, magnesium, and phosphate ions diffuse  

through paracellular


-40-60% urea reabsorbed-nearly all uric acid reabsorbed -water follows solutes by osmosis through both paracellular and  transcellular routes through water channels (aquaporins) -sodium reabsorption: creates osmotic and electrical gradient that  drives reabsorption of water and other solutes  

-symports that simultaneously bind Na+ and another solute such as glucose,

amino acids, or lactate  

-Na+–H+ antiport that pulls Na+ into the cell while pumping out  H+ into tubular


∙ Describe the location(s) in the nephron where tubular secretion occurs. 

-renal tubule extracts chemicals from capillary blood and secretes  them into tubular fluid  

-proximal convoluted tubule  

-nephron loop

-distal convoluted tubule

∙ Compare and contrast tubular reabsorption and secretion, with respect

to the direction of solute movement, strength of concentration  gradients, and energy required.  

-tubular reabsorption: process of reclaiming water and solutes from the tubular fluid and returning them to the blood

-solutes move out of cells

-tubular secretion: renal tubule extracts chemicals from capillary blood  and secretes them into tubular fluid

-solutes move into cells

∙ Describe how the renin-angiotensin-aldosterone system, ADH, and  atrial natriuretic peptide each work to regulate reabsorption and  secretion  

-renin-angiotensin-aldosterone system works to restore fluid  volume and blood pressure when it drops  

-aldosterone stimulates reabsorption of sodium and secretion of  potassium

-ANP is secreted by heart in response to high BP

-leads to secretion of more salt and water in urine thus reducing blood  volume and pressure  

-ADH secreted by pituitary in response to dehydration and rising blood osmolarity  

-makes collecting duct more permeable to water so water reenters  tissue fluid  

∙ Explain why the differential permeability of specific secretions of the  renal tubule is necessary to produce dilute verses concentrated urine.  -depending on the permeability of the secretion determines how much  water leaves  

-more water leaving=more concentrated urine

-less water leaving=more dilute urine

∙ Predict specific conditions that cause the kidneys to produce dilute  versus concentrated urine.  

-salinity in renal medulla affects how concentrated the urine gets  -fluid flowing downward passes through descending limb which is  permeable to water which can lead to more concentrated solution  

-fluid flowing upward in ascending limb is impermeable which leads to  more diluted urine  

∙ Explain the role of the nephron loop, the vasa recta, and the  countercurrent mechanism in the concentration of urine.  -countercurrent multiplier: because of fluid flowing in opposite  directions in adjacent tubules of nephron loop, nephron loop  continually recaptures salt and returns it to extracellular fluid of  medulla which multiples the salinity in adrenal medulla

-vasa recta-capillary branching off efferent arteriole in medulla -provides blood supply to medulla and does not remove NaCl and urea from

medullary ECF-returns reabsorbed water to bloodstream

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