GI, Liver, Spleen, Pancreas Histology

Mucosa (mucous membrane)
Submucosa
Muscularis externa 
Serosa (or Adventitia)

Muscularis mucosae -
2 layers of smooth muscle:
inner- thin circular
outer- longitudinal .

Lamina Propria
No, the innermost layer is the Epithelium with its Basal Lamina

A nerve plexus derived from neural crest that is part of the ENTERIC NERVOUS SYSTEM.
It is found in the submucosa.

Inner circular and outer longitud layers of smooth muscle.
Between- Auerbach (Myenteric) plexus
(part of ENTERIC-NS)

(both layers are same inside- loose CT w vessels)

if it is a Serosa layer- covered by mesothelium

if it is an Adventitia- it is surrounded by and blends to the adjacent CT

Esophageal Cardiac Glands - secretes neutral pH mucus to protect from regurgitated acid

Stays closed until bolus of food comes close, then opens.

Muscularis Mucosa, *** but it only has longitudinal layer

Pyrosis

Barretts esophagus

Esophageal glands proper - secretion of these glands is slightly acidic and functions to lubricate the lumen of the esophagus
(most numerous in LOWER esophagus)

*By the Muscularis Externa!
Upper 1/3 - Skeletal muscle only
Middle 1/3 - Mixture of skeletal and smooth
Bottom 1/3 - Smooth Muscle only

Above diaphragm- Adventitia (Loose CT w longitudinal vessels)

Below diaphragm- Serous (free part of esophagus just before the stomach is covered with mesothelium)

Cardia

(heartburn)

Lamina Propria
Cardia - mucus secreting cells
Fundus- Short pits, Long glands
Pyloric- Long pits, Short glands

Neck (Undifferentiated cells)

(and Secrete different secretion than the surface mucus cells)

Parietal/ Oxyntic cells- upper part

Chief/ Zymogenic cells- lower part

Parietal Cells

Splits H+ from Carbonic Acid using Carbonic anhydrase-->
actively pumps H+ out of cell from invaginations in apical membrane to elaborate HCl

Secret Intrinsic Factor

Parietal cells

--test question, if problem w B12, prob Parietal cells

Pernicious Anemia (Low RBC and hemoglobin)

B12 deficiency--> CNS degenerate (sensory disturbances like burning feet)
*may present like MS

Chief (Zymogenic) cells

Chief (Zymogenic) cells

cleaved in the acidic environment of the lumen to become pepsin

Gastric Enteroendocrine cells

Stuff diffuses into nearby cells in lamina propria

Gastrin stimulates acid production

inner- oblique

middle- circular – (thick) forms the pyloric sphincter

Outer- longitudinal

Plicae Circulares= Permanent (core of SUBmucosa)
Villi (core of lamina propria, has Lacteal--main lymph vessel)
Absorptive cells w microvilli (core of Actin microfil's)

Villi, Lamina Propria (core of mucosa)

Microfilaments (Actin)

Crypts of Liberkuhn

Paneth Cells

Duodenum, increase in frequency going down the anal canal

Enteroendrocine cells

M (microfold) cells

Enterocytes
(ie the cells that secrete the IgA made by Plasma cells of the Lamina Propria into the lumen)

Increase absorptive surface area

Lamina Propria

Duodenum (Brunner's Glands - secrete alkaline stuff to buffer acidic chyme when it enters)

Submucosa

Auerbach's plexus
(nerves and postganglionic neurons)

(primary plexus of small intestines; where the parasympathetics running around the SMA lead to)

M (microform) cells
Phagocytose organisms from the intestinal lumen and present to T lymphocytes in the Lamina Propria
(part of GALT)

Plasma cells in lamina propria make IgA --> Enterocytes release IgA to lumen

(goblet cells and enteroendocrine cells)
Crypts of Lieberkuhn (in lamina propria)
Brunner's gland (in submucosa)

Chyme (super acidic) from the stomach forces Brunner's gland to secrete an Alkaline. It optimizes pH for Pancreatic enzymes

CCK- stimulates release of gallbladder/pancreatic bile and enzymes, and inhibits gastric empyting.

GIP- Shuts off acid production in stomach

Secretin- stimulates pancreatic secretion, inhibits gastric acid production

Thickening of the inner circular layer of muscularis externa= Pyloric Sphincter

Transition from pyloric to intestinal mucosa: Villi, Goblet cells begin, glands in the submucosa begin

Jejunum- bigger plicae circulares, rounded Villi, less goblets than ileum

Ileum- Peyer's Patches, club-like villi, more goblet cells

to absorb water and dehydrate poop and to lubricate for its passage down

Villi

the outer longitudinal layer is made of TENIAE COLI and is way thicker
(3 distinct longitudinal bands)

No Paneth cells in the crypts, but
Some Enteroendocrine cells

Goblet cells

Haustra Coli

Semilunar folds

Appendix

(does NOT have tinea coli though)

Internal sphincter- smooth muscle (thickening of internal circular layer of musc extern) relaxes w parasymp, tightens w/ symp.

External Sphincter- skeletal muscle, innervated by the inferior anal (rectal) nerves, branches of the pudendal nerve (S2, S3, S4).

the liver

skin

Liver

Endocrine

to help digest fats

Exocrine

Parenchyma

Portal vein- 75% - deoxygenated but rich with nutrients from GI tract

Hepatic artery- 25%- oxygenated

IVC on posterior aspect of liver

Bile and blood flow in OPPOSITE directions.

Portal vein- branches lead into venules that empty into sinusoids

Hepatic A- branches lead into arterioles that empty into sinusoids

<25% arteriole, 75% venous blood>

Bile duct- branches receive bile from 'canals of Hering' which drain the bile canaliculi

***Lymphatics ALSO in region of Triad, but not included in the triad**

CLL model is based upon direction of blood flow.
-hexagon-

The lobule= central vein in center w/ radiating plates of hepatocytes, separated by sinusoids and portal triads

*pig liver used for emphasis of shape

The PL model is based upon the direction of bile secretion.

Triangular= Portal triad at center of portal lobule, Central veins make up the 3 corners

(not used)

Diamond shaped acinus= 2 central veins and 2 portal triads create the 4 corners, w/ center having the terminal branches of the portal triad

Bc of creation of 3 zones based on oxygen, nutrient, and toxin levels in blood of Acinus:
1- closest to vessels; higher nutrient, oxygen, and toxin levels; higher metabolic rate; first to show changes from bile occlusion; last to die from no circulation and the first to regenerate

3- farthest from vessels but closest to terminal hepatic vein; first to show ischemic necrosis; first to show fattyness; last to respond to toxins

Zone 3 is downstream and is can get toxin fallout from other zones

zone 3 = central lobular

Ischemic necrosis of the lobule is called 'Centrilobular necrosis' because Pathology follows the Central Lobular model---the central vein is in center.

In Liver Acinus model, that central vein is in Zone 3 (the zone that is the first to show necrosis)

1. Fatty Liver- alcoholics accumulate liver fat, first in centrilobular hepatocytes (3), liver can gain x3 mass, reversible w cessation

2. Hepatitis- Inflammatory/ Nectrotizing to the central zone (3)- marked by neutrophils , can kill

3. Cirrhosis- (irreversible) scarring of liver--> portal hypertension/ liver failure; fibrous septa form around nodules--> structure + fcn compromised

Cardiac Cirrhosis

Hepatocytes in zone 3 susceptible to ischemia and hypoxia; no change to zone 1 and 2

sinusoids

Special capillaries w/:
- dilated lumen
- discontinuous endothelial lining and basal lamina
- Fenestrae with NO diaphragm

Kupfer cells- phagocytize aged RBCs

Ito cells- store vitamin A

Disssssse space

blood and stuff hits hepato microvilli

90% reabsorbed from GI

10% created by hepato

Bile Canaliculi

Bile from hepatocytes --> canals of Hering --> bile ducts of portal triads

Sealed by Tight junctions

CCK

Bile from hepatocytes --> canals of Hering (ductules) --> bile ducts of portal triads

Bile ducts converge --> Hepatic duct

R&L Hepatic duct coverge --> Common Hepatic duct

Common Hepatic duct joins the Cystic duct ---> Common bile duct --> Ampulla of Vater --> Duodenum

Simple columnar Absorptive cells w/ Microvilli

Forms mucosal folds that absorb water and concentrate bile
**Inside the folds there can be glands/ sinuses that secrete mucus


***NO SUBMUCOSA IN GALLBLADDER

It doesnt exist dummy

RUQ/ Epigastric pain

Referred pain to R shoulder from irritation of inferior diaphragm

Brown pigment stones related to increased concentration of unconjugated BILIRUBIN in bile

Basophilic RER and acidophilic Zymogen granules
*Base of cell- basophilic
*Apex of cell- acidophilic

True, dummy

CCK from duodenum's Enteroendocrine cells

and

Parasympathetic (Vagus) stimulation

---------

Secretin from the duodenal enteroendocrine cells

Intercalated ducts (cuboidal cells)-->
Intralobular ducts-->
Interlobular ducts (columnar cells)-->
Main Pancreatic Duct (in head of pancreas)-->
Joins with Common Hepatic Duct --> Ampulla of Vater

Islet of Langerhans

Kupffer cells (macrophages in the sinusoids)

Sickle cell anemia and portal hypertension

White- lymph nodules (filters and immuno-surveys the blood)

Red- FILTER; degrades old RBCs (breaks down and recycles iron and hemoglobin)