BIOL 204 Exam 1 lecture 3

Does the enterogastric reflex stimulate or inhibit gastric acid secretion

Inhibit

Does CCK stimulate or inhibit gastric acid secretion

inhibit

Does secretin stimulate or inhibit gastric acid secretion

inhibit

Does lower pH stimulate or inhibit gastric acid secretion

inhibit

Does acetylcholine stimulate or inhibit gastric acid secretion

stimulate

Does increased pH stimulate or inhibit gastric acid secretion

stimulate

Does food stretching stomach walls stimulate or inhibit gastric acid secretion

stimulate

Does histamine stimulate or inhibit gastric acid secretion

stimulate

Does sight taste, or smell of food stimulate or inhibit gastric acid secretion

stimulate

Does gastrin stimulate or inhibit gastric acid secretion

stimulate

What happens when food arrives in the duodenum from the stomach

Chemoreceptors detect lower change in PH and chemical composition of food

Stimulate the release of CCK and secretin

CCL and secretin act on the stomach liver, gallbladder and pancreas

CCK and secretin effect on stomach

slow acid production and movement

after food arrives in duodenum

Secretin effect on liver

secretion of bicarbonate and water by cholangiocytes

CCK affect on gallbladder

increases the secretion of bile through contraction

CCK effect on pancreas

more enzyme secretion by acinar cells

CCK and secretin at the level of liver and gallbladder

CCK acts on the gallbladder to release bile

secretin in cholangiocyte stimulates secretion of bicarbonate

CCK and secretin at the level of the gallbladder

Secretin stimulates bicarbonate

CCK stimulates the release of digestive enzymes

All go into the ampulla of vater

Ampulla of vater

storage area of pancreatic juice, controlled by sphincter of oddi

Sphincter of oddi

Controls secretion of Ampulla of vater

Pyloric sphincter

separates the stomach from the duodenum

regulates the passage of chyme

What controls the flow from the ileum into the large intestine

Ileocecal valve

Ileocecal valve

ileal papila

sphincter controlling flow from the ileum into the cecum of the large intestine

is the Ileocecal valve a true sphincter

false

Duodenum location

Duodenum function

Neutralizes chyme from stomach

uses duodenal glands

which secretes bicarbonate and intestinal juice

Duodenal glands

in duodenum

secrete bicarbonate and intestinal juice

Pancreatic juice in duodenum makeup

bicarbonate and digestive enzymes

bile in duodenum makeup

bicarbonate and bile salts

Pancreatic juice in duodenum makeup

bicarbonate and digestive enzymes

where Duodenal glands

in the duodenum, neutralize chyme Duodenal glands

Jejunum

in small intestine

digestion and nutrient absorption

ileum

absorption of vit B12 and reabsorption of bile salts

Order of small intestine

Duodenum, jejunum, ileum

Segmentation

in small intestine, rhythmic contractions of circular smooth muscle

mixes chyme with digestive enzymes and increases contact with mucosa for absorption.

minimal net forward movement

Where are circular folds mainly at

in the jejunum

Brush border

collection of villi on the surface of each enterocyte

Circular folds

series of transverse folds along the intestinal lining, mosty in jejunum

Villi

in small intestine, in the circular folds, mostly in jejunum

form a brush border on surface of each enterocyte

villi cross section

blood capillaries in villi

absorb most food molecules

lacteal in villi

absorb digested villi

Brunners glands

intestinal glands

submocosa that serve as a protective role

produce mucus that have bicarbonate ions, neutralize the acidic gastric juice that enters the duodenum

Crypts of lieberkuhn

produce intestinal juice (DIGESTIVE/ASORPTIVE ROLE)

intestinal juice secretions

secretin, CCK, mucus, antimicrobial peptides

Enteroendocrine cells

in villi in small intestine, create intestinal juice

secrete hormones

(secretin, CCK)

S cells

Type of Enteroendocrine cell that create Secretin

in villi in small intestine

I cells

Type of Enteroendocrine cell that create Secretin

in villi in small intestine

Goblet cells

in villi in small intestine, create intestinal juice

secrete mucus for lubrication

Tuft cells

in villi in small intestine

chemosensory epithelial cells that detect luminal signals and initiate immune responses, especially parasitic infections

Paneth cells

in villi in small intestine, create intestinal juice

secrete antimicrobial peptides

Villi anatomy

2 Major functions of large intestines

absorption of water and electrolytes ( formation of feces)

absorption of vitamins produced by gut bacteria

Vitamins that the large intestines absorbs

K B7(biotin) B5

What is movement in the large intestine done by?

smooth muscle

Does the muscosa of the large intestine have villi?

no

colon mucus

lots of goblet cells in the colon, which lubricates feces, leading to easier passage

protects epithelium from mechanical damage

irritating acids and gases produced by bacteria

Cecum

first part of large intestines

colon

second part of large intestine

rectum

third part of large intestine

anal canal

fourth part of large intestine

Ascending colon

Transverse colon

Descending colon

sigmoid colon

Muscularis externa

In large intestine

inter circular layer remains continuous throughout the wall

outer longitude layer reduced to 3 bands

paritally contract colon leading to the “baggy” appearance

Tenia Coli

In large intestine

Semilunar folds

In large intestine

encircle part of the colon’s circumfrence

Haustra

In large intestine

parts of colon bulging outward (haustrum)

allow for expansion and elongation

Taenia

In large intestine

Omental apendages

In large intestine, unknown function

Sacs of fat in the serosa

Haustral contractions

Segmentation like,

local back and forth contraction of the colon in haustra

mixes the intestinal content

maximizes contact with mucosa, allowing water and electrolyte absorbtion

Key point: segmentation does not move feces forward much

Peristalsis in large intestines

coordinated wave of contraction behind the fecal mass

relaxation ahead of it

propels contents fowards (towards rectum)

Mass peristalsis

pooping enticing reflex

strong peristaltic waves

move feces across large segments of the colon at once

1-3 times a day

done by gastrocolic reflex

Gastrocolic reflex

stomach fills with food ENS in the stomach wall initiates a reflex that stimulates the colon to contract (promoting mass movements) this reflex helps move food residue towards the rectum, making space for new food intake

Defecation reflex

normally internal anal sphincter and external anal sphincter is contracted,

but upon rectal distension of the stool, the internal anal sphincter will voluntarily relax

Internal Anal sphincter

smooth muscle

parasympathetic NS

external anal sphincter

striated muscle

excretion of stool controlled by voluntary relaxation of the external anal sphincter

somatic NS

Initiation of poop reflex in smooth internal anal sphincter

Mass movements push feces into the rectum, which activates stretch receptors

sensory nerve fibers relay information about distention of the rectum

spinal parasympahtetic reflex activated

contraction of the rectal smooth muscle

relaxation of internal anal sphincter (smooth muscle, involuntary)

DEFACTACATION IS NOW POSIBLE, BUT NOT YET ALLOWED

Initiation of poop reflex in external internal anal sphincter

After internal external sphincter becomes relaxed

sensory info goes to cerebral cortex and you are made aware of the urge to defecate

(allows voluntary control to come into play)

voluntary motor neuron then goes to external anal sphincter via the cerebral cortex

if defecation is not appropriate, external anal sphincter contracts a

rectum relaxes later

defecation is postponed

how much human cells do we have

30 trillion

how much microbial cells do we have

39 trillion

Where is the highest concentration of enteric bacteria

large intestines (800 species)

Gut microbiome

alll microorganisms living in your digestive system

unique to every person microscopic ecosystem

Function of gut microbiome

humans lack enzyme to digest many fibers, beneficial gut bacteria use fiber as a food source.

production of important vitamins

trains and regulates the immune system via helping it distinguish helpful and harmful pathogens

prevents colonization by pathogens via direct competition

Function of gut microbiome - fiber digestion

bacteria ferment SCFAs like butyrate, the promary source of energy for colon epithelial cells, which helps maintain a strong intestinal barrier

SCFAs

Done by gut microbiome

short chain fatty acids like butyrate which are the primary source of energy for colon epithelial cells

Helps maintain a healthy strong intestinal barrier and have anti-inflammatory effects

Vitamins produced by microbiome

B vitamins like

B12, folate, biotin