Lecture 87-93

Air: nasopharynx
Food/Air: Oropharynx, laryngopharynx

Ciliated, pseudostratified columnar epithelium with goblet cells

(in nasal cavity, nasopharynx, larynx, trachea, bronchi)

Stratified squamous epithelium

oral cavity
stomodeum is an ectodermal invagination

From ectodermal nasal placodes that invaginate as nasal sacs which break through oral cavity

1. Mucosa: epithelium, lamina propia, muscularis mucosae (simple columnar)
2. Submucosa: lose to desne connective tissue, has MEISSNER'S PLEXUS, BLOOD VESSELS
3. Muscularis externis: inner circular, AUERBACH PLEXUS, longitudinal layer
4. Serosa: simple squamous epith, with some C.T.

They mark the junction of the embryonic stomodeum and foregut

1. Sublingual: mucosal
2. Parotid: serous
3. Submandibular: both

Can be keratinized or parakeratinized if nuclei are retained

1. Filiform: sad bc no tastebuds
2. Circumvallate: big ass
3. Fungiform: lonely little mushrooms
4. Foliate: regularly spread out

Penetrate up to 1/2 thickness of mucosa
Glands are TUBULAR and BRANCHED

1. surface mucous
2. neck mucous: found in neck of gland
3. parietal
4. chief
4. entteroendocrine

- H+ from carbonic anhydrase
- H+ into canaliculis via H+/K+ ATPase pump (Cl- also delivered into canaliculis)

They secrete pepsinogen and they are found in basal half of glands

The small pyramidal cells with granules are found at BASE OF CELL.

Mostly you find mucous secreting cells. Very few chief, parietal cells.

It has THREE layers:
1. inner oblique
2. middle circular
3. outer longitudinal

They are born in the ISTHMUS (middle of the gland)
1. Can migrate up to become mucous
2. Can migrate down and differentiate into chief, parietal and enteroendocrine

1. Plicae circularis: mucosa and submucosa
2. Villi: mucosa
-Contains an artery, capillary network, vein, blind-ending lamphatic capillary called a lacteal
3. Microvilli

Intestinal glands are called crypts of Lieberkuhn
They are simple tubular invaginations that penetrate lamina propia -> so deep they almost reach muscularis mucosa!

Enterocyte

It absorbs fatty acids, carbs, proteins

It is antibacterial.
It is found at the base of crypts

An M cell is involved in iMmunity.
It grabs antigens and presents them to immune cells found underneath in PEYER'S patches

They are born at the bottom of the cryps of Liberkuhn

enterocytes and goblet cells turn over rapidly

enteroendocrine cells and Paneth cells turn over slowly

sucrase, maltase, lactase, aminopeptidase, phosphatase, etc

salivary amylase, pancreatic amylase in duodenum, brush border, glucose and galactose are actively transported to exit base, capillaries

They are found in the duodenum
They secrete bicarbonate and PEPTIDE GROWTH HORONES
They are continuous with Crypts of Lieberkhun

Pepsin: cleaves large proteins
Pancreatic trypsin, chymotrypsin, carboxypeptidase produce fee amino acids and small peptides which are taken up by active transport

Micelles with fatty acids diffuse in, they are re-esterified to make triglycerides, combined with apolipoproteins to make lipoprotein particles (chylomicrons) which are secreted into intercellular space to enter capillary or lacteal

It has NO villi

Yes, but very few

1. Normal inner circular layer
2. Outer longitudinal layer is condesned into THREE THICK BANDS CALLED TENIA COLI

2 sheets of visceral peritoneum with C.T. and fat in between
-route for blood vessels, nerves and lymphatics

simple squamous epithelium
also knonwn as SEROSA or MESOTHELIUM

1. common cardinal veins
2. Pleuroperitoneal membrane (from septum transversum)

Celiac artery, superior mesenteric artery, inferior mesenteric artery

It is the abdominopelvic cavity proper, a sac of pareital peritoneum that forms from the breakdown of midgut and hindgut ventral mesentery

The OMENTAL FORAMEN, aslo known as EPIPLOIC FORAMEN

Under the free edge of the lesser omentum
VENTRAL MESOGASTRIUM

1. Rotation of foregut, stomach 90 degrees to the right
2. Looping of midgut around the SUPERIOR MESENTERIC ARTERY
3. Tremendous growth of small intestine

Omphalocele is midgut herniation WITHIN the umbilical cord
Covered with amnion
Happens when small intestines do NOT return to their place after week 10.

Gastroschisis is organ herniation THROUGH A VENTRAL BODY WALL DEFECT: it is NEVER within the umbilical cord
It is covered by amniotic fluid
Happens because of INCOMPLETE FOLDING OF THE GASTRULA

It is gastroschisis of the heart
remember the poor little babies

1. Lesser omentum: hepatoduodenal, hepatogastric
2. Falciform ligament
3. Coronary ligament

The GREATER OMENTUM
1. Gastrophrenic ligament
2. Gastrosplenic ligament
3. Gastrocolic ligament
4. Splenorenal ligament

It contains the portal triad

1. Hepatic artery
2. Bile duct
3. Hepatic vein

Ventral mesogastrium

It has dorsal and ventral buds that fuse dorsally.
Its ducts join bile duct

Spleen is a condensation of mesenchyme; it is NOT derived from the foregut, but it is associated with it.
Spleen is found in dorsal mesogastrium

All of them associated to MESOCOLON

gastrocolic
phrenicocolic
hepatocolic

ligamentum teres (round ligament of the liver)
ovarian ligament
round ligament of the uterus

kidneys, adrenal glands, aorta, IVC, bladder, prostate, vagina, rectum

PANCREAS, duodenum, ascending and descending colon

The extrinsic controls are the neuronal and hormonal
The intrinsic are the innate properties of the tissues, GI hormones and the ENTERIC NERVOUS SYSTEM

The hindgut (last 1/3 of the transverse colon, descending colon...) is innervated by the pelvic splanchnic nerve.
Preganglionic neuron in sacral segment 2 to 4. Postganglionic neurons in pelvic ganglia or intrinsic ganglia of the colon

Mostly cholinergic
Mostly excitatory: increases motor and secretory activity

T5 to L3

On smooth muscle cells of arterioles
On neurons of intrinsic plexus

They are adrenergic
Usually inhibitory to GI
Constricts blood vessels

1. oropharynx
2. external anal sphincter

1. Meissner plexus - SUBMUCOSAL PLEXUS - found in submucosa
2. Auerbach plexus - MYENTERIC plexus - found between longitudinal and circular muscle of the muscularis externa

1. from nervous system: sympathetic or parasympathetic
2. Chemo and mechano receptors
3. GI hormones

Innervation of GI smooth muscle, mucosal cells and glands

Slow waves are found in the stomach and in the intestine.

Lower frequency in stomach than intestine.

In the intestine frequency decreases as you move from duodenum to ileum

They spread due to fluctuations in Na+ permeability from longitudinal layer through gap junction into circular layer.

Slow waves by themselves DO NOT cause contractions.

Need deploarizing input from intrinsic or extrinsic nervous system for contraction to occur.

(acetylcholine)

1. Determines frequency at which contracton can occur
2. Determines speed of propagation

1. stretch
2. acetylcholine
3. parasympathetics

1. Norepinephrine
2. Sympathetics

storage
there are no slow waves in the proximal stomach

Trigger: swallowing
Vagus nerve releases: VIP (vasoactive intestnal peptde), NO
Causes receptive relaxation which DECREASES PRESSURE

The stomach pressure increases much faster than normal when eating

mostly inhibitory since you want it to RELAX

Mostly excitatory:
gastrin and acetylcholine are released -> elicit contraction so stomach can CHURN and GRIND

In the antrum of the stomach

Distenton of the stomach

Presency of chyme in duodenum is inhibitory (you don't want to be emptying tons of stuff into small intestine if you haven't had time to absorb)

Hormones involved are Sympathetic: norepinephrine
Duodenum: secretin
Duodenum: CCK

In the antrum of the stomach

Distenton of the stomach

Presency of chyme in duodenum is inhibitory (you don't want to be emptying tons of stuff into small intestine if you haven't had time to absorb)

Hormones involved are Sympathetic: norepinephrine
Duodenum: secretin
Duodenum: CCK

1. propulsion: bolus pushed toward pylorus
2. grinding: antrum churns trapped material
3. retropulsion: bolus is pushed back into the proximal stomach

Gastric emptying

Promoted by distention of the stomach: vago-vagal and intrinsic reflexes are activated

Depending on volume, somolarity, pH, chemical composition and quality of chyme

The release of CCK (released in Duodenum, Jejunum and Ileum): which INHIBITS gastric motility and stimulates pancreatic enzyme secretion and gall bladder contraction

1. propulsion: bolus pushed toward pylorus
2. grinding: antrum churns trapped material
3. retropulsion: bolus is pushed back into the proximal stomach

Gastric emptying

Promoted by distention of the stomach: vago-vagal and intrinsic reflexes are activated

Depending on volume, somolarity, pH, chemical composition and quality of chyme

The release of CCK (released in Duodenum, Jejunum and Ileum): which INHIBITS gastric motility and stimulates pancreatic enzyme secretion and gall bladder contraction

It causes the release of secretin in the DUODENUM (nowhere else in small intestine) which inhibits gastric motility and stimulates bicarbonate secretion from the pancreas.

1. Peristalsis
2. Segmentation
3. Migrating Motor Complex during interdigestive period

1. Peristalsis
2. Segmentation
3. Migrating Motor Complex during interdigestive period

Peristalsis AND Segmentation

Peristalsis AND Segmentation

progressive relaxation and contraction of CIRCULAR smooth muscle that moves aborally

function is to push stuff down

short-lived

progressive relaxation and contraction of CIRCULAR smooth muscle that moves aborally

function is to push stuff down

short-lived

Segementation is circular contractions separated by relaxed segments

function is MIXING

occurs most of the time

Occurs in small intestine and first half of colon in fed state

Segementation is circular contractions separated by relaxed segments

function is MIXING

occurs most of the time

Occurs in small intestine and first half of colon in fed state

Wave of activity that occurs in fasting state/
Begins at pacemaker of stomach and travels through stomach and small intestine

Entirely INTRINSIC

Wave of activity that occurs in fasting state/
Begins at pacemaker of stomach and travels through stomach and small intestine

Entirely INTRINSIC

the gastro-ileal reflex

the Cecal-ileal reflex

Haustral contractions

haustral shuttling

They are antidiarrheal.
They increase segmentation (takes longer to digest)

From evagination of embryonic foregut

1. EXOCRINE -> majority of the function
2. Endocrine

Pyramidal serous cells that make up to compound tubuloacinar glands (acini)

Carried out at tail of pancreas by islets of Langerhans

The pancreatic duct is called the duct of Wirsung, and it empties out at the ampulla of Vater

The duct of Santorini

The basal half is crowded with rER that makes all of the digestive enzymes (zymogens)
The concave face packages zymogens into condensing vacuoles

proteases, glycosidases, lipases, nucleases

A: glucagon, REALLY dark circle in EM
B: insulin, MOST of the endocrine cells, has weird DENSE shapes made of Zn-Insulin crystals
D: somatostatin, not very impressive. Inhibits A and B cells.

Most B cells are found in the center, most A cells are found in the periphery

It inhibits B cells, preventing release of insulin
It stimulates A cells, releasing glucagon to increase blood sugar

Stimulates BOTH of them!

Develops from the hepatic diverticulum

1. Anastomosing plates that are one cell thick
2. TWO Sinusoidal surfaces lined by discontinuous fenestrated endothelium
3. Space of Disse
4. Bile canaliculis
5. Dual blood supply

1. Regulation of blood (endocrine) and bile (exocrine)
2. Conversion and redistribution of nutrients absorbed by the gut
3. Detoxification

2 coming in, 1 coming out.
Coming in:
Portal vein (75%): rich in nutrients
Hepatic artery: rich in oxygen, branch of the celiac trunk

Central vein collects blood -> large hepatic veins -> IVC

Liver acinus: center of acinus is fed by portal vein and hepatic artery, blood flows bilaterally into 3 regions and empties into the 2 central veins at the periphery

1. sinusoidal: space of Disse -> ENDOCRINE function
2. lateral
3. bile canalicular (apical surface)

1. old RBC are macrophaged by Kupffer cells in liver (also in spleen)
2. bilirubin is released from Hemoglobin
3. hepatocytes esterify it with glucuronic acid and secrete into bile canaliculi

by bile route, they leak through tight junction

Can be transcytosed

they line sinuosids in discontinuous fashion, fenestrated, no diaphragms, space of disse allows exchange between hepatocytes and blood

resident macrophages of the liver. Kill RBC

They live in the liver and have fat storage of Vitamin A

The gall bladder's CYSTIC DUCT, and the liver's HEPATIC BILE DUCT, connect to from the COMMON BILE DUCT, which joins the pancreas' duct of WIRSUNG, before finally reaching the Ampulla of Vater.

1. It has unusually large intercellular spaces at the base during water transport.
2. No muscularis mucosa
3. No submucosa
4. Mucosal layer is irregular network of fibers in all directions -> very messy

both. Adventitia where it connects to liver

Gallbladder sinuses that extend into and through the muscular layer -> site for chronic bacterial infections, and where gall stones can end up.

Gall bladder has branched tubuloalveolar mucous glands

Secrete bicarbonate and mucous

After fatty meal, "I" cells in duodenum release CCK, CCK relaxes sphincter of Oddi and bile is released

It can be binucleate