GI

graph TD
    X[Intestine] ==> X1[Mucosa] & X2[Sub-Mucosa] & X3[Smooth Muscles] & X4[Adventia];
    X1 ==> X1a[Epithelium] & X1b[Lamina Propria] & X1c[Muscualris Mucosa];
    X2 ==> X2a[Connective Tisue];
    X3 ==> X3a[Longitudinal and Horizontal Smooth Muscle];

Nerve Supply to Smooth Muscles

graph TD
    X[Meissner's Plexus] -.Supply.-> Xa[Smooth muscle of Mucosa];
    Xa -.FunctIon.-> Xa1[COmpress Mucosa epithelium];
    Y[Aurbach's Plexus/Myentric Plexus] -.Supply between .-> Ya[Vertical and Horizontal SM];
    Ya -.Function.->Ya1[Peristalsis];

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Esophagus

Layers of Esophagus

Mucosa	Submucosa	Muscualris Externa	Serosa/Adventia
Stratified non-Kerotinized Squmous Epithelium	Dense irregular Connective Tissue	Upper 1/3 - Skeletal Muscles(regurgitation)
MALT- Mucosa Asscoiated Lymphoidal Tissue	Submucosal glands	Middle 2/3 - SKeletal Muscle and Smooth muscle
Smooth Muscle layer innervated by Meissenrs' Plexus		er 1/3 - Only Smooth Muscle

At junction of Stomach and Esophagus the Stratified Squmaous Epithelum changes suddly to Simple Columnar Epithelium and secrete Bicarbonate ions to buffer acid

Stomach and Intestine

Stomach

1. Secretion of Enzymes = rich in glands ,no villi.

Characteristics	Stomach	Intestine
Mucosa	Simple Columnar Epithelium with pits and Glands	Simple Coloumnar Epithelium wit Pits and Villi

Stomach Pits and Gands

Pits	Glands	Functions
Surface Mucosal Glands		Mucus and Bicarbs : TO protect the Surface Epithelium
	Neck - Mucosa cell	PRotection
	Stem Cells	Proliferate to Replace Damaged cell on Pits and Glands
	Parital Cell, rich in mitochondria to produce ATP for pumping H+ into lumen	HCL and Intrinsic Factor Production under Gastrin
	Enteric-Endothelium	Produce GAstrin
	Chief Cells, basophilic staininge rich in protein	Pepsinogen and Lipase

Zollinger-Ellison Syndrome aka Gastrinoma

Hyper secretion of Gastrin from Entero-Endocrine cell tumor, leads to Gastric and Duodenal ulcer from failure in neutralisation of mucus from Pits and Necks og Gastric Mucosa cells.

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Intestine

Increase Surface Area(Villiception)= Increased Absorption of Nutrients

1. Intsetine loops
2. Sub-Mucosa layer folds(Plica Circularis)
3. Mucosal Layer folds, and pits
4. Micro-Villi on Simple Columnar Epithelium
5. Glycocalyx - Extreacellular matrix

graph TD
    X[Intestine] ==>X1(Dueodenum) & X2(Jejunum) & X3(Illeum);

Cells of Intestinal Mucosa

Cells	Functions
Simple Columnar Epithelial(Enterocytes)	Absorption of nutrients and then into Portal system
	Fat into Lymph via Chylomicrons
Goblet cells	Mucus for lubricator and protection
Paneth cells ant the Pits	Like macrophage produce Granules to digest bacteria
Entro-Endocrine Cells(Secretin and CCK)	For bicarbonate secretion in Duodenum

Duodenum vs Jejunum vs Illeum

Duodenum	Jejunum	Illeum
Vili - Short(due starting of absorption)		Villi -longest (most absorption)
Mucosa - Burnner's gland (protection against Acid from stomach)		Pyer's Patch- immune function

Large Intestine

1. no villi ,glands for Motilin secretion- no need for absorption 2. Mucosa rich in Goblet cells(lube for feces) 3. outer Longitudianl layer thick - For feces pushing