Upper GI tract Flashcards by The Forbidden Fruit

What is digestion

Process of breaking down macromolecules to allow absorption

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What is Absorption

Process of moving nutrients and water across a membrane

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What are the different ways in which a substance can go from ingestion to excretion

Draw it

Ingestion to digestion to absorption / excretion

either you end at absorption or excretion but you don’t have to be absorbed

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What is the margins of the foregut, midgut and hindgut

Foregut- Pharynx to pyloric sphincter

Midgut- dueodenum to 2/3rd proximal part of transverse colon

Hindgut- distal 3rd oif transverse colon to anus

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What are the layers of the gut wall from lumen going downwards

Mucosa

submucosa

muscularis

serosa/Adventitia

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What are the features and structure of the mucosa layer of Oesophagus

Mucosa has secretory functions

1st layer is squamous epithelium

2nd layer is lamina propria (loose connective tissue)

3rd layer is muscularis mucosae

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What is the submucosa layer of the oesophagus

Connective tissue containing nerve plexus

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Extensively describe the muscularis layer of the Oesophagus gut wall

what innervates them

It’s smooth muscle containing nerve plexus (myenteric plexus of the enteric nervous system)

divided into 2 layer: outer circular layer and inner longitudinal layer

they both help in peristalsis

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Contrast the ways in which circular muscles and longitudinal muscles work to bring about peristalsis in Oesophagus

Circular muscles: constrict at different locations to allow oesophagus to hold food

longitudinal: allow bolus to pass down

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What is the Serosa/Adventitia

Connective tissue with/without epithelium

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What are the muscles of the oral cavity

Masseter muscle; largess jaw muscle that is responsible for biting

several muscles control the position of mandible

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What is the fucntion of the salivary gland

They secrete saliva (containing aqueous secretions and diegesitv enzymes). This mix with food

the enzymes are: Lingual lipase and Salivary amylase

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What are the different muscles in the tongue and relate them to their functions

Intrinsic muscles: fine motor control and moving food. E.g. longitudinal and transverse muscle

Extrinsic muscle

gross movement of tongue like protrusion, retraction
Asssits mechanical digestion
e.g. Platoglossus, styloglossus, hyoglossus, Genioglossus

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What is the fucntion of the Oesophagus?

Conduits for food, drink and swallowed secretions form pharynx to stomach via neck, thorax and into abdomen

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Describe the epithelium structure and function of the Oesophagus epithelium

Non- keratinising stratified squamous ; doesn’t make keratin

Lubrication- mucus secreting glands and saliva to lubrications food and hence easily allow muscle to move it down

wear and tear lining (extreme of temperature and texture)

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What is the purpose of the upper and lower oesophageal sphincter

UPPER: this muscle controls how much food enters Oesophagus

LOWER: controls how much food leaves the Oesophagus

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Describe the structure and function of the muscles of the Oesophagus

Tonically acitve

Acts as swallowing centre

Peristalsis

N.B. AS YOU MOVE More supeirorly, there’s more skeletal msucle. As you move down inferiorly, there’s a combination to skeletal and smooth muscle until it’s completely smooth muscle

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Descirbe how Barretts oesophagus can form and it’s prognosis if nothing is done

Chronic acid reflux form stomach into Oesophagus

Hence Oesophagus sqamous epithelial cell is converted to columnar (same type that lines the stomach) in order to cope with the acids; making more mucus. THIS IS METAPLASIA

Metaplasia can lead to dysplasia which can then become cancerous if not monitored.

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Describe the purpose of the gastro- oesophageal junction

Reflux - prevented by diaphragm

Epithelial transitions: they have different functions

Gastirc folds: ruggae- this is to increase SA for absorption as it contains villae

there’s pressure difference between thorax and abdomen hence there’s ligaments that prevent collapse of Oesophagus

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At what vertebrae does the Oesophagus start and end

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Start at C5

end at T10/T11 (just after oesophagus hiatus)

Describe and explain the stages of swallowing

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Superior muscles contract and inferior muscles relax

What are the functions of the stomach?

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Breaks food into smaller particles (acid and pepsin)

Holds food, releasing it in controlled steady rate into duodenum

Kills parasites and certain bacteria

Can people survive without their stomach?

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Yes, people with gastric cancer .

*Research how*

What does the following part of the stomach make

Cardia and Pyloric region
Body and fundus
Antrum

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Cardia and Pyloric region: Mucus only
Body and Fundus: Mucus, HCl, pepsinogen
Antrum: GASTRIN

What do Tubular glands do?

Invaginate into mucosa

How much acid is made in the stomach a day and whats the concentration

2L/day 150mM H+ (3 million ties more than that in blood)

What is te pH of the epithelium surface and lumen of the stomach respectively

Epithelium surface - 6-7 lumen- 1-2

What are the mucins (made by stomach)

Gel coating they are HCO3- trapped in mucus gel

What are the different types of CELLS in the stomach and what do they make?

CHIEF CELLS- Pepsinogen PARIETAL- HCl G cells- GASTRIN D cells- somatostatin Surface mucus cell/Fovealar cells- HCO3-/mucus

What are the different effects brought about by stomach muscle wall contractions. Quantify them

Peristalsis - 20% stomach contractions Segementation- 80% contractions

Contrast peristalsis and segmentation of the stomach

Peristalsis * Propels chyme towards colon * more powerful as it moves from LOS to pyloric sphincter * Autonomic nervous system is essential Segementation * Weaker than peristalsis * fluid chyme flows towards pyloric sphincter * solid chyme pushed back to body * Stretching activates enteric nervous system

Descirbe the features and functions of Gastric Chief cell

Abundant in RER and Golgi for making and packaging and modifying protein for export It contains masses of apical secretion granules Secretes pesinogen - ultimately coveted to Pepsin its a protein secreting epithelial cell

Contrast the features of a Resting and secreting **parietal** cell

Resting * Has **cytoplasmic tubuloveiscle** (which contains H+/k+ ATPase) * Has internal canaliculi which extends to apical surface * Has lots of mitochondria Secreting * the Tubulovesicles **fuse** with membrane * Microvilli project into canaliculi

Describe the process in which HCl is released from parietal cell

CO2 enters cell from capillaries and combine enzyamtically (carbonic anhydrase) to make **ultimately** H+ and HCO3- (after H2CO3 has dissociated) HCO3- exchanged for Cl- via AE1 transporters H+/K+ ATPase releases H+ out and takes in K+; using ATP Cl- accumulated is also released

Describe how pepsin is formed form pepsinogen

HCl helps to convert pepsinogen to pepsin Pepsin acts as a auto catalyst

What is the purpose of G cells?

They are located in pyloric antrum they make GASTRIN- this stimulates parietal cell to make more HCl they also stimulate histamine release from chromaffin cells (lamina propria) peptic ulcer could be due to imbalance of these cells

What are the 3 phases of Gastric Secretion

Cephalic phase Gastric phase Intesitnal phase

desciribe the cephalic phase

Smell/thought of food integrated in medulla and signals sent down via parasympathetic fibre (VAGUS NERVE) to stomach this stimulates all the part of the stomach to make respective secretions (pepsinogen, HCl etc) GASTRIN relasesd in the blood stream further stimulate HCl and Pepsin secretion

Extensively describe the Gastric phase. DRAW IF POSSIBLE

Food in stomach is stimulus theres stretch in stomach and stretch receptors and chemoreceptors send signal up to medulla via vagus parasymapthetic fibres via vagus sent down to simulate production of more HCl and pepsin There's also local reflexes

Descirbe the intesitnal phase of Gastric secretion

Presence of **lipids and low pH(lower than 2)** in **duodenum** send signals up to medulla via vagus nerve This decreases PNS activity; less stimulation and secretion of HCl, GASTRIN etc Also Enterogastrones are made: * Gastric inhibitory peptide * Cholecystokinin- makes bile * Secretin- inhibit secretion of pepsin

Draw a parietal cell and what factors affect it's secretions

ECL- chromaffin like cells

There are different stimulus that affect intesitnal phase. Outline them and explain the downstream effects. draw them

What factors affect cephalic phase and explain it's effects

Loss of appetite and depression- ultimately inhibits secretory secretory activity sight /thought of food. Stimulation of taste/smell receptors

What is the function of somatostatin

Inhibits G cells; hence GASTRIN secretions

Explain the different stimulus that can affect gastric phase (both stimulators and inhibitory)

Label this structure

There different types of muscles in muscularis of Oesophagus. Describe the distribution down the Oesophagus

Upper GI tract Flashcards

(48 cards)