Exam 3

Describe the difference between the alimentary canal (GI Tract) and the accessory organs:

Alimentary Canal:

• Tube food passes through

• Digests and absorbs

  Accessory Organs:

• Structures (organs , glands) aid in digestion

List the regions of the GI tract and the accessory organs of the digestive system:

GI tract

• Mouth, Pharynx, Esophagus, Stomach, Small Intestines, Large Intestines

Accessory Organs

• Teeth, Tongue, Salivary Glands, Pancreas, Liver, Gall Bladder

Distinguish between mechanical and chemical digestion:

Mechanical- Physical Breakdown

Chemical- Enzymatic breakdown into smaller compounds

Identify the four layers of the wall of the digestive tract and their basic functions:

Muscosa- Epithelial Lining

Submucosa- CT Layer

Muscular Externa- Muscle Layer

Serosa- Covering

Differentiate between peristalsis and segmentation:

Peristalsis- Moves material through gut

Segmentation- Helps mix material with digestive enzymes in small intestine

Describe the general neural and hormonal controls over digestive function:

Enteric Nervous System:

• Enteric neurons control GI muscle contraction

  • Control smooth muscles and glands

    Receive CNS motor input from ANS:

  • Parasympathetic - Increase GI activity

  • “Rest and Digest”

• Sympathetic - Decrease GI activity

  • “Fight or Flight”

Describe the gross anatomy of digestive tract from the mouth through the esophagus:

-Mouth: site for chewing, bolus created and pushed back into pharyx
-Pharynx: muscular funnel that connects oral cavity to esophagus
-Esophagus: muscular tube that carries food into stomach

Describe the muscular control as food moves from the mouth to the esophagus and towards the stomach:

Waves of muscle contractions called peristalsis force food down through the esophagus to the stomach. A person usually isn't aware of the muscle movements that push food through the digestive tract. The stomach: At the end of the esophagus is a muscular ring or valve called a sphincter

Describe the composition and functions of the components of saliva:

Salivary Glands Two groups:

Intrinsic – buccal glands

Extrinsic (3 pairs)

1. Parotid glands 2. Sublingual glands 3. Submandibular glands.

Salivary Proteins

Mucin - Lubricating glycoprotein

Lysozyme - Bacteriostatic enzyme

IgA = Abs

Defensins - Antibiotic/chemotactic neutrophil secretion

Salivary amylase - Hydrolyzes starch

Describe the neural control of salivation

ANS Control

Sympathetic - ↓ salivation

Parasympathetic - ↑ salivation

Psychological Control - Response to visual/olfactory stimuli

Can be stimulated by lower GI irritation

Explain the extent to which digestion/absorption occurs in the mouth through the esophagus.

Digestion/Absorption – Mouth to Esophagus

* Ingestion

* Mechanical digestion - Mastication by teeth. - Formation of bolus.

* Chemical digestion - Salivary amylase breaks down starch/glycogen

* Deglutition (swallowing) then peristalsis

- Voluntary (mouth)

⇒ reflexive (pharynx)

⇒ involuntary (end of esophagus – smooth muscle)

* Absorption = NONE (except some drugs) e.g. nitroglycerin

Contrast the structure of the gastric mucosa with that of the esophagus.

Mucosa – stratified squamous epithelium

Submucosa – mucus-secreting esophageal glands

Muscularis – skeletal ⇒ smooth

Describe the gross and microscopic anatomy of the stomach.

Cardiac region

Cardiac sphincter

Fundus

Body

Greater & lesser curvatures

Pyloric region

Pyloric sphincter

Describe how the muscularis of the stomach differs from that of the rest of the GI tract.

Unique qualities

Simple columnar epithelial mucosa ⇒ In folds called rugae

3-layer muscularis

3 sections

1. Surface epithelium

2. Gastric pits

3. Gastric glands ⇒ Secretes gastric juice

List the four types of epithelial cells in the pits of the gastric mucosa.

Mucus neck cells ⇒ Bicarbonate-rich mucus

Parietal cells ⇒ HCl

Chief cells ⇒ Pepsinogen (inactive form of protease pepsin)

Enteroendocrine cells ⇒ Release hormones carried to digestive organs by the blood

Identify the secretions of these cells and state their functions.

Enteroendocrine Cell Products

Gastrin – MOST IMPPORTANT ⇒ ↑ gastric cell activity, gastric emptying, contraction of SI & LI, ileocecal valve relaxation.

Histamine - ↑ H + secretion

Endorphins – kill pain

Serotonin - ↑ contraction of stomach SM

Somatostatin (also secreted by SI) ⇒ Inhibits stomach, pancreas, SI, gall bladder.

Explain the extent to which digestion/absorption occurs in the stomach

Mechanical Digestion ⇒ Mixing waves

Chemical Digestion ⇒ HCl (parietal cells) activates pepsin (chief cells) which becomes protease (breaks down protein

Movement ⇒ Peristalsis into SI

Absorption ⇒ Only lipid-soluble substances. E.g. aspirin, alcohol

Describe the three modes by which gastric activity is regulated (activated/inhibited)

Hormones ⇒ Gastrin (increases) vs. somatostatin (inhibits)

Neural Control

⇒ ANS - Parasympathetic increases. - Sympathetic decreases

Local enteric nerve

⇒ Distension of stomach activates stretch receptors. - Stimulates stomach.

⇒ Distension of SI (duodenum) - Inhibits stomach

Contrast cephalic, gastric, and intestinal regulation of the stomach.

Cephalic Regulation of Stomach

Stimulation of stomach

Think food

⇒ See, taste, smell, etc.

⇒ Vagus nerve of PS ANS increases activity

Inhibition of stomach

Think otherwise

⇒ ↓ appetite & depression decreases PS ANS

⇒ Emotional upset increases S ANS

Gastric:

Gastric Regulation of Stomach

Stimulation of stomach

Stomach distension ↑ PS ANS

↑ pH (caffeine/ peptides)

Inhibition of stomach

No stomach distension

↓ pH

Intestinal:

Intestinal Regulation of Stomach

Stimulation of stomach

Slight drop in pH & partially-digested food in duodenum ⇒ Secretes gastrin

Inhibition of stomach

Duodenum distension; fatty, acidic, hypertonic chyme

* Enterogastric reflex

⇒ Inhibits PS ANS (Vagus)

⇒ Activates S ANS (closes pyloric sphincter)

* Inhibitory intestinal hormones (example: somatostatin)

Differentiate among the following gastric conditions: gastritis and gastric ulcers.

Gastritis

Inflammation of underlying layers of wall

Gastric ulcers

Erosion of stomach wall

Helicobacter pylori associated with 80-90% of ulcers

Describe emesis

Emesis = vomiting

Caused by:

⇒ Extreme stretching of stomach/SI

⇒ Irritants (bacterial toxins, excessive alcohol, spicy foods, some drugs)

Emetic center:

⇒ Increases abdominal pressure

⇒ Relaxes cardiac sphincter

⇒ Raises soft palate (closes nasal passages)

Describe the gross and microscopic anatomy of the small intestine.

Functions:

⇒ Secretion (proximal end)

⇒ MOST digestion & absorption of all GI tract

Three areas

⇒ Duodenum – receives chyme

- Duodenal glands (alkaline mucous)

- Hepatopancreatic sphincter (fluids from liver/pancreas)

⇒ Jejunum – duodenum to ileum

⇒ Ileum – jejunum to LI (through ileocecal valve)

State how the structure and function of the mucosa of the small intestine differs from that of the stomach.

Circular folds

- Forces spiral movement of chyme ⇒ Slows movements for ↑ absorption

Villi = Fingerlike projections of mucosa ⇒ Contain capillaries & lacteal

Microvilli = Cell membrane projections

Brush border secretes enzymes

Increases surface area (SA)

Describe how each major class of nutrients is chemically digested.

Describe how each major class of nutrients is chemically digested.

Chemical Digestion

By hydrolysis of macromolecules

Digests (pancreatic enzymes):

⇒ Lipase - lipids

⇒ Proteases - Large peptides → small peptides → AAs

⇒ Amylase - Starches → disaccharides → monosaccharides

⇒ Nucleases (also nucleosidases & phosphotases) - NAs → nucleotides → sugars, phosphates,bases

Name the substrates (major organic macromolecules), enzymes, and products of digestion.

Digests (pancreatic enzymes):

⇒ Lipase - lipids

⇒ Proteases - Large peptides → small peptides → AAs

⇒ Amylase - Starches → disaccharides → monosaccharides

⇒ Nucleases (also nucleosidases & phosphotases) - NAs → nucleotides →

sugars, phosphates,bases

Describe how each type of nutrient is absorbed by the small intestine.

Nutrients/vitamins move from lumen across cells and into blood/lymph

Nutrient monomers absorbed

⇒ Carbohydrates: monosaccharides into blood

⇒ Proteins: AAs into blood

⇒ Lipids: into lymph

⇒ Nucleic acids: ribose, phosphate, & bases into blood

Vitamins

⇒ Fat soluble into lymph - A, D, E & K

⇒ Water soluble into blood - B & C

Describe the hormonal/neural control of the small intestine.

Hormones

Gastrin - ↑ SM contraction & ileocecal valve relaxation

Vasoactive intestinal peptide (VIP) - ↑ bicarbonate-rich intestinal juices

Neural Control

⇒ PS ANS increases activity

⇒ S ANS decreases activity

Describe the condition known as Celiac disease.

A chronic digestive and immune disorder that damages the small intestine.

Describe the digestive secretions and functions of the pancreas, liver, and gallbladder.

Liver

Largest gland in body

⇒ Produces bile

⇒ Joins cystic duct from gall bladder to form bile duct

Gall bladder - Stores bile

Pancreas

⇒ Secretes digestive enzymes

⇒ Pancreatic duct joins bile duct

Explain how hormones regulate secretions of the pancreas, the liver, and the gall bladder.

Acidic, fatty chyme causes production of

1. Secretin

⇒ Stimulates bile production by liver

⇒ Stimulates secretion of bicarbonate pancreatic juices

2. Cholecystokinin

⇒ Stimulates gall bladder contraction

3. Acetylcholine

⇒ Stimulates secretion of pancreatic enzymes

Differentiate among the following disorders/conditions: hepatitis, cirrhosis, jaundice, and gallstones.

Hepatitis

⇒ Inflammation caused by viral infection

⇒ Transmitted enterically or through blood

Cirrhosis

⇒ Chronic disease & growth of scar tissue

Jaundice

⇒ Yellowing of the skin through buildup of bilirubin from liver disease OR high RBC destruction

Gallstones

⇒ Crystallization of cholesterol due to excess

Obstructive jaundice

⇒ Yellow skin due to bile duct blockage

Describe the gross and microscopic anatomy of the large intestine.

Cecum ⇒ Including vermiform appendix

Colon

Ascending

Transverse

Descending

Sigmoid

Rectum

Anal canal ⇒ Anal sphincter

Contrast the mucosa of the colon with that of the small intestine.

Mucosa

Simple columnar with many goblet cells

Anal canal

⇒ Stratified squamous epithelium

⇒ Anal sinuses secrete mucus

Submucosa

Thinner than in SI

State the physiological significance of intestinal bacteria.

⇒ Resident bacteria dominated by Escherichia coli (E. coli)

⇒ Ferment some indigestible carbohydrates

- Results in mixture of acids and gases

⇒ Synthesizes vitamins B & K

Explain the neurological control of defecation.

- Parasympathetic reflex relaxation of internal anal sphincter (smooth muscle)

- Voluntary control over relaxation of external sphincter (skeletal muscle)

Differentiate among the following disorders/conditions: diarrhea, constipation, hemorrhoids, and appendicitis.

Diarrhea

⇒ Watery stools due to shortened time in LI

⇒ Loss of water leading to dehydration

Constipation

⇒ Hard stools due to longer time in LI

Hemorrhoids

⇒ Inflammation of superficial perianal veins

Appendicitis

⇒ Infection of appendix

List the general functions of the urinary system:

Maintain blood composition and volume:

• Regulating water content

• Maintaining ionic concentrations

• Mainting pH balance

• Removing metabolic wastes (urea)

Other functions:

• Secretes renin (affects blood pressure)

• Secretes erythropoietin (affects RBC formation)

Identify the microscopic anatomy of the urinary system:

Kidneys (Upper lumbar region)

Ureters (Extend from kidney to urinary bladder)

Urinary Bladder (In pelvic cavity; stores urine)

Urethra (Extends from bladder to urethra)

Identify the microscopic anatomy of a nephron:

Afferent and Efferent Arterioles

Glomerulus

Glomerular Capsule

Proximal Convoluted Tubules

Nephron Loop

Distal Convoluted Tubules

Collecting Duct

List the relevant vessels of the renal circulation as they lead to and from the nephron:

Renal Artery and Vein

Afferent and Efferent Arterioles

• Supply blood in and out of the glomerulus to proceed throughout the nephron

Explain the glomerulus and recta/peritubular capillaries:

Blood enters nephrons, a million tiny filtering units found in each kidney. The peritubular capillaries move the blood through the nephrons into filters called the glomerulus. These filters trap fluid, small molecules, and waste in the tubule. Blood cells and proteins pass through the glomerulus harmlessly.

Describe the process by which the kidney filters the blood plasma:

Glomerular filtration is the first step in making urine. It is the process that your kidneys use to filter excess fluid and waste products out of the blood into the urine collecting tubules of the kidney, so they may be eliminated from your body.

Explain the pressures that promote and oppose filtration within the glomerulus:

Difference between pressures forcing fluids into capsular space and pressures resisting filtration

• Hydrostatic pressure within the glomerular capillaries promotes or enhances filtration. The other two forces oppose filtration and are: back pressure from hydrostatic pressure of the fluid within the capsule and colloid osmotic pressure caused by the plasma proteins within the glomerular capillaries.

Distinguish between the cells of the juxtaglomerular apparatus (JG)cells and the macula dense (MD) cells:

JG cells:

Smooth muscle in afferent and efferent walls

Respond to low BP by secreting renin

MD cells:

Osmoreceptors

Detect solute concentration in Distal Convoluted Tubule.

Secretes local vasoconstrictor to decrease flow into glomerulus when filtrate concentration is high

Describe the intrinsic and extrinsic controls over glomerular filtration rate:

Intrinsic:

Autoregulation

• Kidney controls local blood flow on its own

• Stretch response (Afferent arterioles contract during high BP and relax during low BP)

Feedback Mechanism:

• Higher BP

• Higher filtration rates

• High filtration concentration in the DCT

• MD cells in the DCT secrete more (vasoconstrictor)

Describe the intrinsic and extrinsic controls over glomerular filtration rate:

Extrinsic:

Sympathetic ANS modulated

• Rapid control

• Very low BP

  • Vasoconstriction = increase BP

Afferent arterioles also constrict:

• Less blood entered glomerulus

• Lower hydrostatic pressure

• Decreases filtration rate

• Less filtrate (urine) produced

• Less loss of fluids

• Maintain blood volume and blood pressure

Describe how the nervous system, hormones (renin), and the nephron itself play roles in extrinsic and intrinsic filtration rate:

Hormones: reduces glomerular filtration function, decrease in renal blood flow

Nervous system: Parasympathetic and Sympathetic control (controls digestive activities)

Nephron: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.

Explain how these controls can affect blood pressure:

Extrinsic tries to help increase blood pressure and vasoconstriction when BP is low.

Intrinsic helps when BP is too high and vasodilates to help filtration of blood flow and helps lower BP.

Differentiate between tubular reabsorption and secretion:

Reabsorption

• Filtrate → Interstitial Fluid → Blood

Nutrients (Sugars, AA’s, Vitamins)

Ions (Regulated by hormones and pH balance)

Water (Antidiuretic hormone)

Differentiate between tubular reabsorption and secretion:

Secretion

• Blood → Interstitial Fluid → Filtrate

Wastes (Urea and Acids)

Drugs (Aspirin, Penicillin, Morphine)

Ions (Excess potassium, Hydrogen and Bicarbonate)

List the solutes commonly reabsorbed or secreted by the tubules of the nephron:

Reabsorbed: water salt

Secreted: Organic acids/bases, Potassium and Hydrogen,

Describe the normal composition and properties of urine as a result:

Normal:

Substances partially reabsorbed: Water and Salt

Substances secreted into filtrate: Organic Acids/Bases, Potassium and Hydrogen (Creatinine)

(Volume, Transparency, Color, Odor)

Explain how the collecting duct and antidiuretic hormone regulate the volume and concentration of urine:

Process:

• Hypothalamus detects an increase in blood solute concentration

• Posterior pituitary secretes ADH

• Increase ADH signals water pores to form collecting ducts

DCT and CD increase water permeability

• Causes reabsorption of water

  (Increase Blood Volume = Increase Blood Pressure)

Explain how the kidney maintains an osmotic gradient in the renal medulla that enables the collecting duct to function:

Physical draw by the solutes on the more concentrated side of the capillary walls

• Pulling fluids into the blood (Absorption Force)

Describe three mechanisms by which diuresis can occur:

1. Condition that inhibit ADH release (Alcohol/Caffeine)

2. Chemicals that Inhibit Sodium reabsorption (Caffeine)

3. Any solute that exceeds its transport maximum (Diabetes)

Describe how the structure of the waller of urerters, bladder, and urethra differ in composition and function:

Ureters

- Mucosa - Transitional epithelium (allows stretching)

- Muscularis - Smooth muscle (propels urine by peristalsis)

Urinary Bladder

- Located in pelvic region

- Function: temporary storage of urine

- Designed to withstand stretching

- Mucosa - Transitional epithelium

- Muscularis - Smooth muscle

Urethra

- Duct from urinary bladder to outside

- Internal urethral sphincter

- SM under ANS control

- Urethra - Mucosa - Transitional stratified squamous

- External urethral sphincter - Skeletal muscle under voluntary control

Explain how the nervous system and urethral sphincters control urination:

Duct from urinary bladder to outside

• Internal urethral sphincter

  • SM under ANS control

• Urethra

  • Mucosa (Transitional Stratified Squamous)

• External Urethral Sphincter

  • Skeletal muscle under voluntary control

Differentiate among the following disorders / conditions: incontience, bladder infection/UTI and renal calculi

Incontinence

• Inability to control micturition voluntarily

Bladder Infection (UTI)

• Invasion of bladder by bacteria

Renal Calculi (Kidney Stones)

• Crystallization of calcium, magnesium or uric acid salts in renal pelvis