Medsci 201_Alimentary system (stomach, SI, Colon, Liver)

Changes from Pyloric and Duodenum transition zone are:

1. Gastric rugae --> intestinal plicae

2. Gastic pits & glands--> intestinal villi & crypts

3. Secretory epithelim--> simple columnar absorptive enterocytes + goblet cells+paneth cells (defense)

4. Enteroendocrine cells secrete different hormones (gastric--> cholecytokinin)

5. Brunner's glands

Chief cells produce

Pepsinogen production

Parietal cells produce

HCL & intrinsic factor

Intrinsic factor function?

secretion of parietal cells that help absorb B12 vitimin across intestine lining

Enteroendocrine cells produce

Gastrin

Structures found in the core of the intestinal villus

Lacteal

Blood vessels (venules & arterioles)

Functions of Microvilli in SMALL intestine

1. Increase surface area for absorption

2. Glycocalyx coating on top of microvilli bind desired moledules and barrier from undesirable molecules

3. Actin filaments connected to cytoskeleton - locased movement help to mix contents

Give the name of the nerve plexus located between the two layers of muscularis externa.

Myentric plexus

Is there skeletal muscle present in the muscularis externa?

In some regions of the gut tube skeletal muscle is present in the muscularis externa to enable voluntary movement (e.g. in upper oesophagus for swallowing, or the external anal sphincter for controlling defecation).

Origin of undifferentiated epithelial cells of oesophagus?

Undifferentiated (generative/stem) epithelial cells arise from the basal layer of the epithelium.

The muscularis mucosae consists of what type of muscles?

Smooth muscles

Adventitia vs. Serosa

Adventitia is located between two structures (eg. the trachea and the oesophagus).

Serosa lines a body cavity/peritoneal space.

The outermost layer of the abdominal oesophagus is called by ______, which is lined by _____.

Serosa, mesothelial cells

How many tunics in digestive system?

4 layers(tunics)

Name 4 tunics of digestive system

1. Mucosa (epithelium + Lamina propria + Muscularis mucosae)

2. Submucosa

3. Muscularis externa (inner circular + longitudinal outer)

4. Adventitia/Serosa

The outermost connective tissue covering of any organs, vessels or other structure?

Adventitia

Also Known as visceral peritoneum.. what is this?

Serosa

two layered slippery outer covering

Serosa

Outer________ of Serosa sitting on a bed of connective tissue.

mesothelium

Accumulation of fluid; abdominal swelling;distortion of visceral organs. What is this condition called?

Ascites

Complication from surgery, inflammation interferes with normal functioning

Peritonitis

General organization of the alimentary canal

Epithelium of Oesophagus

Stratified squamous epithelium

Oesophagus function

Rapid transport (peristalsis) of food to stomach

Length Oesophgus

25cm long, straight tube, collapsed outline with folds of submucosa when empty

Epithelium of Oesophagus

Non-keratinised stratified squamous epithelium(6-8 layers)

Epithelium of Oesophagus transition to______towards stomach

Simple cuboidal/columnar

Muscularis mucosae in Oesophagus is_____.

Absent/rare but developed near stomach. Longitudinal smooth muscle discontinuous in places

Submucosa of Esophagus is_____________________.

Loose and irregular connective tissue.

Are there glands in Esophgus?

yes.

Muscularis externa of Esophagus move food by ____ and _____.

Peristalsis and Segmentation

Characteristics of Muscularis Externa of Esophagus

2 Thick coats (inner:spiral/oblique and outer:iregularly arranged)

Mostly smooth muscles but, towards mouth some skeletal.

Covering of Esophagus

Adventitia majority, except 1-2cm between diaphragm and stomach

Nerves of Esophagus

Enteric and autonomic nervous system

Storage tank, digestive processes of secretion and digestion and some absorption, what am I?

Stomach

3 regions of stomach

Mucus, acid, enzymes and hormones - Fundus/body

Mostly mucous - Cardia

Mucus, enzymes, hormone - Pylorus

3 muscle layers of stomach

Longitudinal

circular

Olbique (innermost)

Transient fold is called ----

Rugae

Mucous neck cells

produce mucus to lubricate the food entering the stomach

Parietal cells, function

Fried egg looking cell.

secretes HCL, denatures proteins, converts pepsinogen into pepsin

Chief cell, function

production and secretion of pepsinogen; secretion stimulated by ACh and HCl

G cell, function

hormone gastrin (regulatory function)

Simple columnar mucous cells (of surface and pits) of stomach, function

Secreates insoluble alkaline

Elongated nucleus

3 protective mechanisms of stomach cells

1. Mucous gel/surface coat (alkaline)

2. HCO3-

3. High cell turnover via undifferentiated stem cells

Mucous neck cell of gastric glands, function

Soluble, acidic glycoproteins secreted upon food.

Mucous granules less densely packed

Parietal cell

Cells found in gastric glands that secrete hydrochloric acid (for hydrolysis of ingested food) and gastric intrinsic factor (for absorption of vitamin B-12).

secrete HCl

OH- -------> HCO3- in exchange for CL-

HCO3- diffuses into venous blood leaving stomach

Helico Bacter Pyori

Ammonia produced attacks HCO3- of Mucous gel, surface coat.

Toxin blocks/attacks Mucous gel, surface coat.

What inhibits Prostaglandin E2 production?

NSAIDS - aspirin, non steroid anti-inflammatory drugs

Prostaglandin E2

Natural defense of the stomach

Stimulates Mucous gel/surface coat

TBC

Enteroendocrine cell

secrete hormones

Also called G-Cells. It is a secretory cell in the gastric gland of the stomach that secretes paracrine factors and the hormone Gastrin.

Located deep in the gastric glands.

Platelet Activating Factor produced by which bacteria?

Helico Bacter Pyloris

Parietal cell roles

1. Sterilise food

2. Acidify environment (important for Pepsinogen converting to Pepsin)

3.

Not enough acid--->

Gastritis

Intrinsic factor important for......

VtB12

VtB12 involved in

RBC Haemotopoiesis (RBC synthesis)

If low, Pernicious Anaemia

Overactive parietal cells

Exam question

Enteroendocrine cells (secretes hormone released from Basal Lamina) release granules containing _______. ______, _______.

Gastrin - stimulates all cells above (mucosal replacement, activates everything) ---> Activates ECL cells

Gastrin ----> Activates Somatostatin--->negative feedback inhibit ECL cells

Intrinsic factor important for......

Vt12

The fold in small intestine is called _____.

Plica (mucosal fold)

Cells in Villus region in small intestine that absorb small molecules resulting from digestion

Columnar absorptive cell (enterocytes)

Membrane of small intestine is studded with digestive enzymes such as

glucosidases (for breaking down carbohydrates)

Goblet cells in small intestine produce _________ granules filling apical cytolasm.

Mucinogen

Enteroendocrine cells in small intestine produces

Cholecytokinin

Gastrin, histamine, endorphins, serotonin, cholecystokinin, and somatostatin are hormones that are released directly into the lamina propria. Which of the following cell types synthesize and secrete these products?

Paneth cells in Small Intestine(SI), location?

Bottom of crypt of Liberkuhn (intestinal gland)

Paneth cells secret.. name 3;

TNF-alpha: produce inflammatory response

Lysozyme: bactericidal

Defensins: increase membrane permeability of invading organisms (causing cell leakage)

Duodenum: name 4 feathres

Brunner's glands-produce alkaline mucous

Lots of HCO3-

C-shaped

Shortest

pH 1-2

Jejunum: features

Lots of Plicae and Villi for absorption

Straight and 2-5m long

Suspended by mesentary

pH 7-8

Ileum

Peyer's patches (brown coloured lymphatic nodules)

Defence!

3-5m long

The ileocecal valve regulates the passage of materials into this expanded pouch. What is this?

Caecum

In colon, mucosa has plicae or villi like small intestine?

NO, in colon the mucosa does not have plicae or villi. However, mucosal glands (crypts of liberkuhn) are numerous.

Name 2 cell types of Colon mucosa

Columnar absorptive cells and Goblet cells

In Colon, Stem cells in Crypt (mucosal gland) replaces the cells above or below?

Above

In Colon, the Lamina propria contains a dense layer of _______ immediately beneath the surface epithelium(simple columnar).

Collagen

In Colon, the Teniae Coli is present in which part of muscularis externa?

Longitudinal outer

In colon, it is mostly covered by Serosa except for....

Posterior surface of large intestine, that area covered by adventitia.

Internal anal sphincter is composed of _____.

Smooth muscle

External anal sphincter is composed of ____.

Skeletal muscle

End of anal canal is

Anus

Esophagus: cell renewal location/ replacement rate

Basal part of epithelium/ days

Stomach: cell renewal location/ replacement rate

Near neck of gastric glands/ surface in days, deeper in months (as metabolically expensive to replace too often)

Small Intestine: cell renewal location/ replacement rate

Crypts of Liberkuhn/ surface in days, deeper in months

Large intestine: cell renewal location/ replacement rate

Lower 1/3 of glands (Crypts of liberkuhn)/ surface cells only and in days

Anatomical unit of liver

Hepatic lobule

Portal lobule of liver

Liver acinus (functional unit)

diamond defined by two portal spaces and two central veins; supply area of a portal venule and hepatic arteriole

Branch of portal vein

High nutriet, Low O2, Low pressure

Branch of Hepatic artery

Low nutrient, High O2, High pressure

Away from Portal triad (towards Central Vein)

Decrease of Nutrients and O2 as they are used up by the liver cells

Cytological features of hepatocytes

Fat storing cells = in space of Disse, VtA metalolism

Endothelium = lines sinusoids, intercellular openings fenestrated

Kupffer cells = luminal, macrophage-like; prevents obstruction; antibacterial

Kupffer cell

(hepatic or stellate macrophages) in liver sinusoids remove debris and old RBCs

Kupffer cell in lumen of sinusoid function

Prevent obstruction and phagocytosis

Nucleus of Hepatocye is.........

Binucleate Polyploid (double DNA content)

Liver bile flows through.............

Bile canaliculi, Bile duct and Bile ductule

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