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PHARM 111 > Digestive system > Flashcards

Digestive system Flashcards

1
Q

6 essential activities of the digestive process

A

1) ingestion

2) Mechanical breakdown
- chewing (mouth)
- churning(stomach)
- segmentation (SI)

3) Chemical Digestion

4) Propulsion
- swallowing (oropharynx)
- peristalsis (esophagus, stomach, SI, LI)

5) absorption
- starts in stomach, most in SI

6) Defecation

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2
Q

Digestive systems 2 groups of organs

A

1) alimentary canal
- oral cavity teeth tongue
- pharynx
- esophagus
- stomach
- SI
- LI (colon)

2) Accessory Organs
- salivary glands
- liver
- gallbladder
- pancreas

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3
Q

See regions of abdominal digestive organs, slide 6

A

unga bunga

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4
Q

4 basic layers (tunics) of alimentary canal

A

entire alimentary canal composed of 4 tunics

1) mucosa
2) submucosa
3) muscularis externa (SM)
4) serosa/adventitia

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5
Q

tunics: Mucosa (3 parts of mucosa and list functions of mucosa as whole)

A

most internal tunic, touches foodstuff ingested

Epithelium
-stratified squamous (rss abrasion) or simple columnar (abs/secrete, sometimes goblet cells)

Lamina propria
-loose CT
-capillaries (nourishment and abs)
Lymphoid follicles (MALT - deals with ingested pathogens)

Muscularis mucosae

  • SM (moves mucosa)
  • NOT responsible for propelling foodstuff, just mucosa

Functions

  • secretes mucus, digestive enzymes, hormones
  • absorbs end products of digestion
  • protects against infectious disease
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6
Q

Tunics: Submucosa (6 parts and function as whole)

A
  • loose CT
  • Blood and lymphatic vessels, lymphoid follicles, glands, submucosal nerve plexus

Functions

  • support mucosa
  • binds layers together
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7
Q

Tunics: Muscularis externa (3 parts, function as whole)

A

Circular layer

  • SM
  • “sphincter former”

Longitudinal layer

  • SM
  • runs length of tube and helps shorten it

Myenteric nerve plexus

  • autonomic nerves
  • helps coordinate above 2 layers

Functions
-segmentation and peristalsis
-sometimes forms sphincters to control passage/prevent backflow
+thickening of circular layer -> sphincter

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8
Q

Peristalsis (4 steps, purpose)

A

1) Bolus of food arrives in digestive system
2) circular muscles contract behind bolus (pinch)
3) longitudinal muscles ahead of bolus contract (shorten)
4) contraction in circular muscle layer forces bolus forward

Purpose - propel food toward anus

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9
Q

Segmentation

A

nonadjacent segments of alimentary tract organs alternatively contract and relax

  • food moves forward then backward for food mixing
  • SLOW food propulsion occurs
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10
Q

Tunics: Serosa (AKA visceral peritoneum) [2 parts, overall function, retroperitoneal organs/adventitia]

A

PARTS:

1) Loose connective tissue
2) epithelium - mesothelium = simple squamous

FUNCTION
-permit mobility

Retroperitoneal organs have an adventitia:

  • dense irregular CT to bind organs together
  • organ either has serosa or adventitia NOT BOTH
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11
Q

Peritoneum definition

A

serous membrane of abdominal cavity

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12
Q

Parietal peritoneum

A

lines body wall

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13
Q

visceral peritoneum

A

on external surface of most digestive organs

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14
Q

peritoneal cavity (and role of fluid in cavity)

A

cavity between visceral and parietal peritoneum

-fluid lubricates mobile organs

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15
Q

Intraperitoneal organs (and mesentery)

A

-surrounded by peritoneum

HAVE a mesentery

  • double layer of peritoneum
  • route for BVs, lymphatics, nerves
  • holds organs in place and stores fat
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16
Q

retroperitoneal organs

A

Located posterior to peritoneum

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17
Q

The mesenteries (how do they connect)

A

The mesenteries are all cts with eachother

Anterior abdominal wall (falciform ligament) Liver (lesser omentum) stomach (greater omentum) Transverse colon (transverse mesocolon) Posterior abdominal wall

[ () indicates connecting mesenteries]

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18
Q

Enteric NS
(type of nerve supply, fibre types and what link/synapse with)
(2 parts)

A
  • intrinsic nerve supply of alimentary canal
  • linked to CNS via afferent visceral fibres
  • long ANS fibres synapse with enteric plexuses

more neurons than entire spinal cord (over 100 million)

Myenteric nerve plexus
-controls GI tract motility

Submucosal nerve plexus
-regulates glands and SM (including BVs) in mucosa

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19
Q

What are the 3 mechanisms that regulate and control digestive activities

A

1) local factors
2) neural control
3) hormonal control

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20
Q

Local factors

A

primary stimulus for digestive activities including:

  • change in lumen pH
  • physical distortion
  • presence of chemicals (nutrients/chem messengers)
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21
Q

neural control

A

GI movement and chemical secretion is primarily controlled by local factors

Short reflexes

  • triggered by chemoreceptors/stretch receptors in GI tract walls
  • control myenteric plexus

Long reflexes
-involve interneurons and motor neurons in CNS
+providing higher level of control over digestive and glandular activities - generally control large peristaltic waves

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22
Q

Hormonal Control

A

GI tract produces many hormones that affect almost every aspect of digestive F(x)
-peptides produced by enteroendocrine cells)
+endocrine cells in digestive tract epithelium

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23
Q

Boundaries of Oral cavity (4) and what makes them

A

anterior and lateral boundary

  • labium (lip)
  • Cheek

Superior Boundary

  • hard palate
  • soft palate

inferior boundary
-tongue muscles

posterior boundary

  • uvula
  • palatine tonsil
  • root of tongue
  • lingual tonsil
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24
Q

Functions of saliva (6)

A
  • cleanses mouth
  • moistens and dissolves food chemicals
  • aids in bolus formation
  • contains enzymes to begin digestion (oral cavity begins chem digestions)
  • buffers pH (HCO3-)
  • Lubrication
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25
Q

Intrinsic (buccal) salivary glands

  • location
  • f(x)
A
  • scattered in oral mucosa

- keep mouth at baseline level of salivation

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26
Q

Extrinsic salivary glands

  • names (3)
  • location
A
  • parotid, submandibular, and sublingual glands

- outside oral cavity

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27
Q

Review slide 20 for locations

A

EEEEEEEEEEE

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28
Q

Salivary glands cell types (2) and f(x)

A

1) serous cells
- produce watery secretion containing enzymes ions and tiny bit of mucin

2) mucous cells
- produce mucus
- (high in lipid so dont stain well on slide)

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29
Q

Submandibular glands

  • cellular makeup
  • f(x)
A
  • mostly serous, small amount of mucous

- make 60-70% total saliva volume

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30
Q

Parotid gland cellular makeup

A

mostly serous

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31
Q

sublingual glands cellular makeup

A

mucous cells

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32
Q

intrinsic (buccal) glands cellular makeup

A

serous and mucous cells

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33
Q

Composition of Saliva

  • water content/pH
  • electrolytes
  • enzymes
  • proteins
  • metabolic wastes
  • microorganism protection
A
  • 97-99.5% water, almost neutral
  • Na+, K+, Cl-, PO43-, HCO3-
  • salivary amylase (starch -> maltose) lingual lipase (begins fat breakdown)
  • mucin, lysozyme, igA, albumin
  • urea and uric acid
  • lysozyme, IgA, defensins, a cyanide compound
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34
Q

how much saliva produced each day

A

1-1.5L

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35
Q

Control of salivation

A

Intrinsic glands
-continuously keep mouth moist

Extrinsic salivary glands
-produce secretions when
\+smell, taste, sound, sight 
\+Pressure in mouth (chew on tongue)
\+Sleep, fatigue, Fear

NOTE: slide 23 goes into pathways and cranial nerves

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36
Q

Tooth structure (3 parts)

A

Crown

  • exposed part above gingiva
  • covered by enamel: hardest substance in body (Ca2+ salts + hydroxyapetite crystals)

Neck
-connects crown and root

Root
-portion embedded in bone

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37
Q

Dentin

A
  • bonelike material
  • maintain by ondontoblasts of pulp cavity
  • not as hard as enamel
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38
Q

pulp

  • makeup
  • 2 parts
A

-connective tissue, BVs, nerves

Pulp cavity
-crown cavity containing pulp

Root canal
-pulp in root

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39
Q

Cementum

A
  • Calcified connective tissue
  • covers root
  • anchored by periodontal ligament to bone
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40
Q

Deciduous (milk) teeth

5 unique

A
  • central incisor (6mo)
  • lateral incisor (9mo) - biting
  • canine/eyetooth (18mo) - ripping
  • first molar (12 mo)
  • second molar (24mo)
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41
Q

Permanent teeth

-(8 unique)

A 
central incisor (6yr)
lateral incisor (8yr)
canine/eyetooth (12yr)
1st premolar/bicuspid (12yr) - replaces 1st molar of milk
2nd premolar/bicuspid (12yr) - replaces 2nd molar of milk
First molar (6yr)
second molar (12yr)
third molar/wisdom tooth (24yr)
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42
Q

what teeth appear first (typically)

A

lower before upper

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43
Q

Pharynx

A

Oropharynx and laryngopharynx

-allow passage of food, fluids, and air

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44
Q

Esophagus

  • 4 tunics and their makeup
  • tube length/desc (3)
  • f(x) of glands in submucosa
A 
TUNICS
Mucosa -stratified squamous epithelium
submucosa -areolar CT
muscularis externa -circular layer and longitudinal layer
Adventitia - fibrous CT

TUBE

  • flat muscular tube ~25cm long
  • pierces diaphragm at esophageal hiatus (T10)
  • collapsed when not involved in food propulsion

GLANDS
-glands in submucosa secrete mucous for lubrication

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45
Q

2 phases of degulation

-how many total steps

A

1) buccal phase (steps 1)
2) pharyngeal-esophageal phase (steps 2-5)
5 total steps

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46
Q

Buccal phase (step 1 of deglutition)

A
  • upper esophageal sphincter contracted
  • tongue presses against hard palate (voluntary)
  • Bolus forced into oropharynx (involuntary phase begins)
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47
Q

pharyngeal-esopphageal phase (step 2 of deglutition)

A
  • uvula and larynx rise
  • epiglottis closes larynx
  • tongue blocks off anterior mouth
  • upper esophageal sphincter relaxes
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48
Q

pharyngeal-esopphageal phase (step 3 of deglutition)

A
  • constrictor muscles of pharynx contract (food forced into esophagus)
  • upper esophageal sphincter contracts
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49
Q

pharyngeal-esopphageal phase (step 4 of deglutition)

A

food moved through esophagus by peristalsis

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50
Q

pharyngeal-esopphageal phase (step 5 of deglutition)

A

gastroesophageal sphincter opens (food enters stomach)

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51
Q

anatomy of infant (5) and adult oral cavity (3)

A

infant
-Oral cavity is small
-tongue and palate flatter
-epiglottis almost attached to soft palate
-airway and foodway separated except when swallowing
+can eat and drink at same time

Adult
-larynx is lower in neck
-food way and airway cross in pharynx
+cannot eat and drink at same time

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52
Q

Emetic Reflex (6 steps)

A

VOMITING

1) salivation and sensation of nausea
2) reverse peristalsis from upper SI and stomach
3) glottis closes (prevents aspiration), breath held mid inspiration
4) diaphragm and abdominal wall muscles contract to increase intra-abdominal P
5) Esophagus and sphincters relax
6) gastric contents ejected

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53
Q

Digestive Processes in stomach (6)

A

1) mechanical breakdown
2) denaturation of proteins
3) enzymatic digestion of proteins by pepsin (+rennin in infants)
4) secretes intrinsic factor
5) absorption of lipid soluble substances
6) delivers chyme to SI

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54
Q

Response to stomach filling

  • how much hold
  • stomach pressure held constant until
  • how P relatively unchanging ? (2)
A
  • Holds 50mL to 4L (vomit before hit 4L)
  • stomach P remains constant until ~1.5L food injested

Relative unchanging P from:
-Receptive relaxation
+as food travels in esophagus, stomach muscles relax
-Gastric accommodation
+intrinsic ability of SM to exhibit stress relaxation response (when stretch it relax)

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55
Q

what makes up most of the stomach

A

the body

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56
Q

rugae (stomach)

A

folds seen by naked eye
-reason able to go from 50mL-4L
+lose folds as expand

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57
Q

Muscularis externa of stomach

A

longitudinal layer
circular layer
oblique layer - unique

Oblique layer
-facilitates mixing and churning of stomach contents

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58
Q

What branches into a gastric gland in the stomach

A

gastric pit

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59
Q

how much gastric jice produced daily

A

gastric mucosa produces 3L of gastric juice daily

60
Q

mucosa epithelial cell distribution

A

cell types vary in different regions

61
Q

Mucous surface cell (stomach)

A

-secretes mucus (alkaline)

62
Q

mucous neck cell (stomach)

A

secretes mucus (acidic)

63
Q

parietal cell (stomach) secretions and roles

A

-secretes HCL and intrinsic factor

intrinsic factor
-glycoprotein required for absorption of vitamin B12 in SI

HCl
-stomach pH 1.5-3.5
\+denatures protein in food
\+activates pepsin
\+kills many bacteria

SEE ~slide 43 for how parietal cells produce HCl

64
Q 
mucosal protection (3 parts)
-surface cell lifespan
A

1) layer of HCO3- rich mucus protects the epithelial cells
2) tight junctions between epithelial cells - protects deeper layers from leakage
3) Damaged epithelial cells quickly replaced by division of stem cells

-surface cell lifespan 3-6 days

65
Q

Regulation of HCl secretion (stomach)
-3 chemicals
+their F(x)

A

ACh, Histamine, Gastrin

  • stimulate parietal cells through second messenger systems
  • all 3 are necessary for maximum HCl secretion
66
Q

Chief cell secretions (stomach)

A

-Pepsinogen (inactive enzyme) released at base of gastric gland
+activated to pepsin by HCl and by pepsin (pepsinogen not activated until reach stomach lumen)

  • small amounts of lipases
  • rennin in infants (helps with breast milk digestion)
67
Q

Gastric enteroendocrine cells

-

A

-Hormone producing G cell

secrete chemical messengers into lamina propria
-go into BVs so can go elsewhere

68
Q

Gastric enteroendocrine cells: Gastrin from G cells

A

Gastrin released from G cells

  • increase HCl secretion
  • stimulates gastric emptying (minor effect)
  • stimulates parietal cell maturation
  • stimulates chief cells to secrete pepsinogen
  • increases intestine muscle contraction
  • relaxes ileocecal valve
  • stimulates mass movements
69
Q

Gastric enteroendocrine cells: histamine from enterochromaffin-like cells

A

increase parietal cells HCl release

70
Q

Gastric enteroendocrine cells: seretonin from enterochromaffin-like cells

A
  • increases contraction of stomach muscle

- makes 90% of total body serotonin

71
Q

Gastric enteroendocrine cells: somatostatin from Delta (D) Cells

A
  • inhibits secretion from stomach and pancreas
  • inhibits small intestine absorption
  • inhibits gallbladder and liver release of bile

ONLY INHIBITOR DISCUSSED
Table of cell types and what released/do ~49

72
Q

Regulation of Gastric Secretion

  • what mechanisms (2)
  • what phases (3) what events occur in phases
A
  • neural and hormonal mechanisms
  • stimulatory and inhibitory events occur in phases
    1) cephalic (reflex) phase: few minutes prior to food entry
    2) gastric phase: food entering stomach to 3-4 hours later
    3) internal phase: brief stimulatory effect as partially digested food enters duodenum, followed by inhibitory effects
73
Q

Cephalic Phase of Gastric secretion

A

ALL STIMULATORY
-sight, smell, taste, thought of food ->CNS -> (vagus nerve CN X) -> submucosal plexuses - > mucous cells (mucus), chief cells (pepsinogen), parietal cells (HCl), G cells (gastrin)

+myenteric and submucosal plexuses stimulate mixing waves

+elevated pH stimulates chemoreceptors activating myenteric and submucosal plexus (-> all cells and mixing waves… cyclic)

+distention stimulates stretch receptors activating myenteric and submucosal plexus (-> all cells and mixing waves… cyclic)

GASTRIN (still stimulatory) from G cells

  • stimulates chief cells
  • stimulates mixing waves
74
Q

G cell inhibition

-what stim?

A

inhibited at pH below 2

-partly digested proteins, caffeine, high pH

75
Q

Names and what release (SI secretions)
CCK
GIP
secretin

A 
CCK = cholecystokinin,
GIP = Gastric inhibitory peptide (glucose-dependent insulinotropic peptide

RELEASE
CCK and GIP = presence of lipids and carbs
Secretin = decreased pH

76
Q

Intestinal phase of gastric secretion

A

CCK, GIP, secretin
-inhibit Chief cells, parietal cells, peristalsis

Duodenal stretch and chemoreceptors

  • inhibit myenteric plexus
  • ENTEROGASTRIC REFLEX
77
Q

Small intestine Gross anatomy

  • F(x)
  • diameter
  • L of parts
  • length of SI in life
A
  • major organ of digestion and absorption
    +most things absorbed by time leave SI

-Diameter - 2.5-4cm

Duodemun - 25cm (c-shaped)
Jejunum - 2.5m (upper left)
ileum - 3.6m (lower right)

In life only 2-4m long due to muscle tone

78
Q

Structural modifications that increase surface area (SI)

A

-more SA, more nutrient absorption
- circular folds (plicae circulares) ~1cm deep
-villi ~1mm hgih
microvilli ~100-2000nm high

total surface area = 200m^2

79
Q

Intestinal mucosa

  • 7 parts
  • interval for villus epithelium replacement
A

Absorptive cells - simple columnar epithelium
Lacteal - all lipids and fats that go to lymphatics enter lacteal
Goblet cell
microvilli - brush border
enteroendocrine cells - produce hormones
intestinal crypt
Paneth cells - (deep in crypts) release antimicrobial agents
(pic slide ~56)

villus epithelium replaced every 2-4 days

80
Q

Where are villi found in GI tract

A

only in SI

81
Q

Duodenum modifications

A

duodenal glands
-secrete HCO3-
+help neutralize acidity from stomach

82
Q

Ileum modifications

A

Aggregated lymphoid nodules

-lot of Immune cells

83
Q

Jejunum modifications

A

lots folds, great for absorption

84
Q

SI secretions

-4pts

A
  • secreted in response to distension or irritation of mucosa by HYPERTONIC or ACIDIC chyme
  • slightly alkaline (pH 7.4-7.8) and isotonic with blood plasma
  • largely water, enzyme-poor, contains mucus
  • facilitates transport and absorption of nutrients
85
Q

Digestions in SI

  • chars of chyme
  • duration and f(x) of SI
A

CHYME from stomach contains:

  • partially digested carbs and proteins
  • Undigested fats

3-6 hours in SI

  • most water absorbed
  • Nearly all nutrients absorbed
86
Q

How does chyme enter duodenum from stomach

  • 3 steps
  • what vol chyme enters
A

1) propulsion
- peristaltic waves move from fundus to pylorus

2) Grinding
- most vigorous peristalsis and mixing occurs close to pylorus

3) retropulsion
-pyloric end acts as pump
+delivers ~3mL of chyme into duodenum
+simultaneously forces most material backward into stomach

87
Q

requirements for digestion and absorption in SI (3)

A

1) slow delivery of acidic hypertonic chyme
2) delivery of bile, enzymes, and HCO3- ions from LIVER and PANCREAS
3) mixing

88
Q

Ileocecal sphincter/valve

A

closed when chyme exerts backward pressure
- prevents regurgitation into ileum

Relaxes to admit chyme into LI when:

  • Gastroileal reflex enhances force of segmentation in ileum
  • gastrin increases motility of ileum
89
Q

liver

A
  • largest gland in body (~3 LBS)

- 4 lobes based on surface fts (8 based on vascular and biliary supply)

90
Q

Falciform ligament (3)

A
  • suspends liver from diaphragm and anterior abdominal wall (a mesentery)
  • separates right and left lobes
  • round ligament (ligamentum teres): remnant of fetal umbilical vein
  • actually is a mesentary (ventral mesentary
91
Q

Liver: blood supply

A

blood enters liver at porta hepatis via:

1) hepatic arteries
2) hepatic portal veins

blood exits liver through hepatic veins into IVC

THINGS ABSORBED IN GI CAPILLARIES GO TO LIVER FIRST
+first pass metabolism

92
Q

Liver blood supply

5 BVs

A

hepatic veins
hepatic portal vein
inferior vena cava

R. hepatic artery
L. hepatic artery

93
Q

Liver microscopy

A

Liver lobules
-hexagonal structures
-filter and process nutrient rich blood
-composed of plates of hepatocytes radiating from longitudinal central vein
+ventral veins all go to hepatic vein -> IVC

Connective tissue septum separates the hexagonal lobules
+CT septum differs in thickness btwn diff species

  • liver sinusoids (leaky capillaries btwn hepatic plates) [btwn hepatocytes froming series of irregular plates)
  • portal triads
94
Q

Portal triad

A 
portal triad 
-at ea corner of lobule
-composed of :
\+bile duct
\+branch of HPV
\+branch of hepatic artery

portal triad found in middle of portal lobule
-sends blood to 3 sep central veins

95
Q

Kupffer cells (stellate macrophage)

A

in liver sinusoids

self sustaining population of macrophages within liver

remove debris (bacteria, worn out blood cells)

act as a gate-keeper for immune responses

96
Q 
Hepatocyte functions
(6)
A

1) process blood borne nutrients
2) synthesize and secrete hormones
3) storage
4) perform detoxification
5) immune surveillance
6) produce bile

97
Q

hepatocyte function: process blood borne nutrients (6)

A

metabolism
-carb, protein, and fat metabolism

metabolism and detoxification of xenobiotics (CYP450)

Use AAs to make plasma proteins

  • albumins (oncotic P)
  • lipoproteins (VLDL, LDL, HDL, for cholesterol homeostasis)
  • alpha/beta globins for transport: Ceruloplamsin (copper), transferrin (iron), Haptoglobin (hemoglobin), retinol binding protein (retinol), etc.
  • clotting proteins (fibrinogen and prothrombin)
  • anti-clotting proteins (plasminogen, antithrombin III)

make immune proteins (complement and C-reactive peptide)

make apoproteins (lipoprotein metabolism)

converts unconjugated bilirubin (indirect) to conjugated bilirubin (direct)

98
Q

hepatocyte function: synthesize and secrete hormones (4)

A
  • insulin-like growth factor 1 (growth hormone mediator)
  • angiotensinogen (BP and fluid balance)
  • Thrombopoietin( platelet production)
  • hepcidin (iron homeostasis)
99
Q

hepatocyte function: Storage (4)

A

-Fat soluble vitamins (A,D,K,E) and vit B12
-iron and copper
-store glucose as glycogen (glycogenesis); makes glucose from noncarbohydrate sources (glugoneogenesis)
+releases when needed (glyconeolysis)
-fat

100
Q

hepatocyte function: Perform detoxification (1)

A 
Ammonia (NH3) -> Urea
-ammonia is toxic to CNS (Crosses BBB)
-sources of ammonia:
\+colon
\+kidneys
\+erythrocyte breakdown
\+muscle metabolism
101
Q

hepatocyte function: Immune surveillance (1)

A

Kupffer cells (AKA stellate macrophages) destroy bac, worn out erythrocytes, and other foreign substances in food

102
Q

hepatocyte function: Produce Bile

  • how much produce
  • colour
  • content (7)
A
  • hepatocytes produce ~900mL bile/day (~500mg bile acids)
  • yellow-green, alkaline solution

CONTENTS:
1) water (95-97%)
2) bile salts [bile acid (hydrophobic) conjugated with taurine or glycine (hydrophillic)]
+primary acids synthesized by liver from cholesterol (cholic and chenodeoxycholic acids)
+secondary bile acids synthesized from primary bile acids by colonic bacterial enzymes (deoxycholic and lithocholic acids)
3) bilirubin (conjucated/direct) -> metabolism by small intestines bacteria produces stercobilin
4) phospholipids
5)electrolytes (Na+, Ca2+, HCO3-)
6) Xenobiotics (things body trying get rid of)
7) IgA

103
Q

Biliary Tree

A

R/L hepatic duct ->common hepatic duct +input from cystic duct from gall bladder -> bile duct

104
Q

Gall Bladder

A
  • thin walled muscular sac on inferior/anterior surface of liver
  • Stores and concentrates bile by absorbing its water and ions
105
Q

Functional relationship in storage and ejection of bile (4 steps)
-relative movement of blood and bile

A

1) Liver continuously secretes bile
2) bile is stored and concentrated in gallbladder
3) duodenum releases CCK which triggers dilation of hepatopancreatic sphincter and contraction of gallbladder
+ejects bile into duodenum through duodenal ampulla
4) Bile salt emulsifying lipid droplet in digestive tract lumen

-Blood and bile move in opposite directions
+bile go CV -> portal triads
+ blood go portal triad -> CV

106
Q

enterohepatic circulation (4 steps)

A

1) bile salts (cholic and chenodeoxycholic acids) are secreted into duodenum
2) as bile salts travel through SI, allow lipid digestion and absorption to occur
3) 95% bile salts reabsorbed by ileum
4) reabsorbed bile salts travel via hepatic portal vein back to liver where recycled. Only 5% bile salts newly synthesized ea time

107
Q

Digestion in SI

A

Chyme slowly released into duodenum

  • released in small amount so acidity dosent dmg duodenum, needs be buffered
  • hypertonic and low pH, requires constant mixing for proper digesions
  • no fat digestion
  • carbs and proteins are partially digested
  • virtually all nut abs occurs in SI
108
Q

Motility in SI

  • what is most common
  • what initiates
  • where move contents
A

most common motion in SI is segmentation

  • initiated by pacemaker cells (cajal cells)
  • moces contents steadily twd ileocecal valve
  • constant back and forth mixing in SI
109
Q

Control of motility - segmentation

A

Frequency of cajal cell pacemaker activity differs:

+3 /min in stomach
+12-14 /min in duodenum
- 8-9 /min in ileum
+3 /min in colon

110
Q

what controls intensity of segmentation

A

Intensity of segmentation altered by long and short reflexes

Long reflex

  • PNS activity enhances
  • SNS activity decreases

More intense contractions greater mixing effect

basic contractile rhythms of various intestinal regions remain unchanged

111
Q

purpose of segmentation

A

absorption along GI tract

  • only stuff touching lumenal walls can be abs’d
  • segmentation allows constant mixing so more likely abs more nuts

slide 7 has list of what abs in diff regions GI tract

112
Q

Control of peristalsis

  • when occur
  • what occur at this point (3)
A

Peristalsis occurs after most nuts have been absorbed
-at this point segmenting movements wane and the duodenal mucosa begins release of motilin

-peristaltic waves begin in duodenum, sweep slowly along intestine
+move 50-70cm before dying out

-each wave initiated more distally MIGRATING MOTILITY COMPLEX (MMC)
+takes ~2hrs

process sweeps last remnants of meal, bac, and other debris into LI

113
Q

control peristalsis - ACh

  • proximal vs distal impulses
  • mvmnt of chyme/SI segments
A

ACh-releasing (cholinergic) sensory neuron in SI send messages to sev diff interneurons in myenteric plexus, regulates:

  • impulses sent proximally by cholinergic effector neurons cuase contraction and shortening of circular muscle layer
  • impulses sent distally to certain interneurons cause shortening of longitudinal muscle layer and distension of intestine

As result proximal area constricts and forces chyme along tract
-lumen of distal part of intestine enlarges to receive

114
Q

Regulation of pancreatic secretion

  • 4 steps
  • neural input
  • CCK/secretin act on anything else?
A

1) -Acidic chyme enter duodenum causing enteroendocrine cells of duodenal wall release secretin.
- fatty protein-rich chyme induces release of CCK

2)CCK and secretin enter BS

3) CCK induces secretion of enzyme-rich pancreatic juices
- secretin causes copious secretion of bicarbonate rich pancreatic juice

During cephalic and gastric phases
-stimulation by vagal nerve fibres cause release of pancreatic juice and weak contractions of gallbladder

secretin and Cholecystokinin (CCK)
-also stimulates secretion of bile from liver

115
Q

Acinus of pancreas

A

acinar cells (acinus associated) and centroacinar (ducts) are exocrine ducts

  • centroacinar cells makeup small ducts that secrete HCO3-
  • zymogen granules = enzymes stored in acinar cells
116
Q

Pancreas - sphincter of Oddi

A

Sphincter of oddi = hepatopancreatic sphincter

  • muscular valve controlling flow of digestive juices (bile and pancreatic juice)
  • relaxed by hormone CCK
117
Q

Composition of pancreatic juice (2)

A

contains enzymes and electrolytes (mostly HCO3-)
+neutralize acid chyme and provide optimal env

-some enzs are released in inactive (zymogen) form and activated

118
Q

GIP

A

targets pancreas causing release of insulin improving nutrient absorption

119
Q

VIP

A

improves nutrient absorption

120
Q

Absorption of nutrients (5) strucs

A

Villi, microvilli, and large circular folds massively inc SA of SI

  • lacteal
  • blood capillaries
121
Q

Absorption of carbohydrates

A

Salivary amylase

  • begins starch digestion
  • in mouth, destroyed once reach stomach

Pancreatic amylase
-digest starch to oligosaccharides
+oligosaccharides hydrolized by brush border enzymes

122
Q

amylase

-what breaks into single C mols?

A

work on storage forms of carbs (glycogen and starch)

starch brocken by amlase -> short oligosaccharides, maltriose (3C mol), Maltose (2C mol)

Brush border enzs break down into single C mols

123
Q

Absorption of Carbs

-what disach->monosach + exception

A

Dissacharides -> monosaccharides

  • catalysis by Brush border enzymes
  • EXCEPTION = beta-1,4 bonds in cellulose
124
Q

Sucrase

A

sucrose -> glucose + fructose

125
Q

Maltase

A

Maltose -> glucose + glucose

126
Q

Lactase

A

Lactose -> glucose + Galactose

127
Q

Digestion of proteins

A

Pepsin

  • released by chief cells
  • in stomach
  • cleaves proteins into smaller polypeptides

IN SMALL INTESTINE

pancreatic enzymes
+trypsin, chymotrypsin, carboxypeptidase

Brush border enzymes
+ aminopeptidases, carboxypeptidases, dipeptidases

128
Q

Activation of enzymes in SI

A

-tripsinogen –> trypsin
+activated by trypsin and membrane bound enteropeptidase

-chymotrypsinogen –> chymotrypsin
-procarboxypeptidase –> carboxypeptidase
+both activated by trypsin

129
Q

Protein absorption

  • AA abs
  • di/tripeptide abs
A

AA by cotransport with Na+

Dipeptides and tripeptides transported by secondary AT using H+ gradient

130
Q

Chemical digestion of fats

-bile salts

A

-without bile salts SA would be too low to effectively degrade droplet with enzs
+bile salts inc SA by degrading fat droplet
- lipases and other fat degrading enzs digest fats

Bile salts
-modified cholesterol molecules
-polar and nonpolar regions
-form micelles, inc SA of fat droplets
\+polar head face exterior, non-polar tail face inward to droplet

Triglycerides from degredation enter epithelial cell layer and become chylomicrons, becoming secretory vesicles shipped into lacteal

131
Q

bunch of shit on slide 25, idk if important

A
132
Q

Chemical Digestion of nucleaic acids

A

(DNA and RNA)
Absorption: AT via membrane carriers
+absorbed in villi and transported to liver by hepatic portal vein

Enzymes used:
-pancreatic ribonucleases and deoxyribonucleases in SI

after above, brush boarder enzymes:
+ nucleosidases and phosphatases

Final degradation products:
pentose sugars, N-containing bases, phasphate ions
+these are what get abs into capillary blood in billi etc

133
Q

Electrolyte absorption

A

Na+ coupled with abs of glucose and AA

Iron transported into cell where it binds to ferritin

Anions passively follow electrical potential established by Na+

K+ diffuses across teh intestinal mucosa in response to osmotic gradients

Ca2+ absorption regulated by vitamin D and Parathyroid hormone (PTH)

134
Q

Vitamins transport out of lumen

  • water sol (exception?)
  • vitamin B12
  • Fat soluble vitamins
A

Water soluble (except b12)

  • diffusion
  • folows [ ] gradient

vitamin b12

  • AT
  • must be bound to intrinsic factor b4 abs

Fat soluble vitamins

  • diffusion
  • absorbed from micelles tgthr with dietary lipids
135
Q

Water absorption

A
  • 95% water abs in SI by osmosis
  • Water moves in both directions across intestinal mucosa
  • net osmosis occurs whenever [ ] gradient established by AT of solutes into mucosal cells
136
Q

Large intestine

  • 3 unique fts
  • cecum and appendix
A

Unique geatures

1) Teniae coli
- 3 bands of longitudinal SM in its muscularis

2) Haustra
- pocketlike sacs caused by the tone of the teniae coli

3) Epiploic appendages
- fat-filled pouches of visceral peritoneum

saclike cecum lies below ileocecal valve and contains a wormlike veriform appendix

137
Q

veriform appendix f(x)

A

thought to store good bacteria

138
Q 
Large intestine (colon) mucosa
-anal canal
A
  • simple columnar epithelium except in anal canal

- anal canal has stratified squamous epithelium that merges with true skin surrounding anus

139
Q

Colon modifications

  • what lack
  • what has and f(x)
A

-No circular folds, villi, almost no cells that secrete digestive enzymes

-mucous produced by goblet cells
+eases passage of feces
+protects intestinal wall from irritating acids and gases

140
Q

Motility in LI: haustral contractions

A

Haustral contractions
-slow segmenting movements lasting ~1min that occur every 30min
-occur mainly in Transverse and descending colon (rare in DC)
+reflect local controls of SM within walls of individual haustra

-as haustrum fills with food residue, distension stimulates its muscle to contract
+propels luminal contents into next haustrum

141
Q

Motility of LI: mass movements and reflexes

-bulk

A

Mass movements
-contractile waves that move over large areas of colon 3-4x/day and force contents twd rectum

Presence of food in stomach activates

  • gastroileal reflex in SI
  • Gastrocolic reflex in colon

Bulk (fiber)
-in diet inc str of colon contractions and softens the stool
+pulls H2O into LI and softens stool

142
Q

LI (fx)

  • digestion
  • reclamation
  • major f(x)
  • essential for life?
A

Other than digestion of enteric bacteria, no further digestion takes place

vitamins, H2O and electrolytes (K+, HCO3-, H+, Cl-, Na+ )reclaimed

MAJOR FUNCTION
-propulsion of fecal material twd anus

Not essential for life, but convenient able control when defecate

143
Q

Colon bacteria

  • where from and f(x)
  • what release
  • how much gas/day
  • what synthesize
A

remaining bac from SI colonize colon

  • metabolize some host derived proteins (mucin, heparin, hyaluronic acid)
  • ferment some indigestible carbs (cellulose, xylan, others)

release irritating acids and mix of gases (dimethyl sulfide, H2, N2, CH4, CO2)

~500mL gas (flatus) produced each day
+more when certain carb rich foods (sa beans) eaten

Synthesize B complex vitamins and most of vitamin K Liver requires to synthesize some of clotting proteins

144
Q

Anus

  • pectinate line (2)
  • superficial venous plexuses (hemroidal veins)
  • inflammation of SVP
  • sphincters (which is voluntary/involuntary)
A

pectinate line - line in anus structure
+superior (above line) - mucosa innervated by visceral sensory fibres and relatively insensitive to pain
+inferior (below line) - very sensitive to pain (somatic fibers)

Two superficial venous plexuses associated with anal canal

1) part of anal columns
2) anus

-if these hemorrhoidal veins are inflamed, itchy varicosities called hemorrhoids form
+prolapsing (fall out anus)
+internal hemorrhoids - not painful
+external hemorrhoids - very painful

External anal sphincter = conscious control

internal anal sphincter = involuntary control

145
Q

Defecation

  • how occur
  • voluntary signals control what sphincter
A

How occur
-distension of rectal walls by feces
+stimulates contraction of rectal walls
+relaxes internal anal sphincter (involuntary)

Voluntary signals
-stimulate relaxation of external anal sphincter and defecation occurs

PHARM 111 (5 decks)

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