Gastrointestinal Tract - Structures + Layers Flashcards by Aífe Hayden

What is another word for the GI tract?

The alimentary canal

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List the six structures of the alimentary canal.

Mouth
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine

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List the five accessory organs of the alimentary canal.

Teeth

Tongue

Salivary glands

Liver

Pancreas

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List the five functions of the digestive system.

Mechanical breakdown
Digestion
Secretion
Absorption
Excretion

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What is digestion?

The chemical breakdown of food

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What is secreted in the alimentary canal?

H2O

Enzymes

Buffers

Acid

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What is absorbed in the alimentary canal?

Substrates

Ions

Vitamins

Water

Minerals

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What is excreted in the alimentary canal?

Waste

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How many phases of digestion are there?

Three

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What are the three stages of digestion?

Cephalic-phase

Gastric-phase

Intestinal-phase

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What is the cephalic-phase of digestion?

• Control of gastrointestinal function by stimuli arising in the head (long reflexes)

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What are long reflexes?

Stimuli arising in the head e.g. sight or sound

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What is the gastric-phase of digestion?

Control by stimuli arising in the stomach (short reflexes)

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What is the intestinal phase of digestion?

Control by stimuli arising in the small intestine (short reflexes)

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What is the peritoneum?

A serous membrane encapsulated with peritoneal fluid

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What is a serous membrane?

A membrane that lines the cavities in the bodies

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How many parts are there to the peritoneum?

Two parts

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What are the two parts of the peritoneum?

Outer parietal membrane

Inner visceral membrane

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What is the outer parietal membrane?

It lines the inner surface of the body wall

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What is the inner visceral membrane?

It covers the organs of the peritoneal cavity (also called the serosa of the GIT)

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What is often known as the serosa of the GIT?

The inner visceral membrane covering the organs of the peritoneal cavity

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Name a condition of the peritoneum.

Peritonitis

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What is peritonitis?

Abnormal accumulation of peritoneal fluid

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What conditions is peritonitis associated with?

Liver disease/cirrhosis

Renal disease

Heart failure

Infection

What is the characteristic feature of peritonitis?

Abdominal swelling

What are two clinical signs of peritonitis?

Heartburn/indigestion Back pain

What is a mesentery?

A doubled sheet of sandwiched peritoneum

What is the function of mesenteries?

They form access routes for blood/lymph vessels and nerves

Where are organs of the GIT suspended?

They are suspended within the peritoneal cavity

What is the greater omentum?

Adipose tissue secreting a number of “hormone-like” substances called adipocytokines

What are adipocytokines?

substances that are 'hormone-like' secreted by adipose tissue

How many layers are there to the tissues of the GIT?

Four

Name the four tissues of the GIT.

Mucosa Submucosa Muscularis Externa Adventitia / Serosa

What is another name for adventitia?

Serosa

What is the mucosa? | 3

The inner lining of the GIT It includes the epithelium and lamina propria There are regional differences in the mucosa - e.g. microvilli

What types of tissue are found in the mucosa? | 2

Epithelia Lamina propria

What are enterocytes?

Cells of the intestines

Describe the epithelia of the mucosa.

Simple or stratified depending on region

Describe the lamina propria of the mucosa. | 4

Loose irregular connective tissue Blood/lymph vessels Nerves Muscularis mucosa

Where is the muscularis mucosa found?

Just underneath the epithelia

Describe the submucosa. | 6

Dense irregular connective tissue Exocrine glands Larger blood/lymph vessels Enterogasterones Chemoreceptors, stretch receptors, osmoreceptors Submucosal/intrinsic nerve plexus

What type of connective tissue is found in the submucosa?

Dense irregular connective tissue

What do the exocrine glands in the submucosa secrete?

Buffers and mucus

What are enterogastrones?

Any hormone secreted by the mucosa/submucosa of the duodenum in the lower gastrointestinal tract

What are chemoreceptors?

A sensory cell or organ responsive to chemical stimuli

What are stretch receptors?

A sensory receptor that responds to the stretching of surrounding muscle tissue and so contributes to the coordination of muscle activity

What are osmoreceptors? | 2

Cells which are sensitized to osmotic pressure. Osmotic pressure changes with the concentration of solutes in the body.

What is the submucosal/intrinsic nerve plexus? | 2

Chain of interconnected neurons The main control for GI secretion and local blood flow

Describe the muscularis externa. | 4

Transverse (circular) & longitudinal layers of SM Regional differences Peristalsis (motility) & segmentation Myenteric intrinsic nerve plexus

What type of muscle is found in the muscularis externa?

Transverse (circular) and longitudinal layers of smooth muscle

What is the muscularis externa responsible for?

Peristalsis and segmentation

What is segmentation?

Localized contractions of circular muscle of the muscularis layer of the alimentary canal

What is the serosa/adventitia? | 5

The outermost layer Visceral peritoneum Loose irregular CT covered by simple squamous epithelia Double layered mesentery, houses vascular and nervous supplies to the GIT Adventitia at oesophagus

What type of the peritoneum is found in the serosa?

Visceral peritoneum

What type of connective tissue is found in the serosa?

Loose irregular CT

What type of epithelia are found in the serosa?

Simple squamous epithelia

What houses the nervous and vascular supplies for the GIT?

The double layered mesentery of the serosa

In which part of the body is the serosa called the adventitia?

In the oesophagus