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Lecture 5 Flashcards

1
Q

What composes the GI tract?

A

Four concentric layers (tunics), series of glands which are outside the tube-proper and they empty their secretions into the tube.

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2
Q

What are the four tunics in the GI Tract?

A
  1. Mucosa.
  2. Submucosa.
  3. Muscularis externa.
  4. Adventitia/Serosa (visceral peritoneum).
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3
Q

What makes up the Mucosa?

A
  1. Epithelium.
  2. Lamina propria.
  3. Muscularis mucosae.
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4
Q

What is the function of the epithelium in the GI tract?

A

Could be the functions below, depending on the organ:

  1. Protection.
  2. Secretion.
  3. Absorption.
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5
Q

What is the function of the lamina propria in the GI tract?

A

Support:

i) Connective Tissue - Structural and physical support.
ii) Blood vessels, nerves and lymphatic’s - functional support.

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6
Q

What is the function of the muscularis mucosae?

A

Helps in movement independent of peristalsis.

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7
Q

What is the function f the submucosa?

A

Support:

i) Connective Tissue - Structural and physical support.
ii) Blood vessels, nerves and lymphatic’s - functional support.

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8
Q

What makes up the Muscualris Externa?

A

There are two layers of muscle (except the stomach = has three).

  1. Inner Circular.
  2. Outer Longitudinal.
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9
Q

What is the function for Muscular Externa?

A

It helps in moving food down the GI tract.

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10
Q

What is Adventitia?

A

Outer connective tissue covering of any organ, vessel (tunica adventitia), or other structure.

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11
Q

What is Serosa?

A

A.k.a. Visceral Peritoneum.
It is a slippery outer covering for the gut tube, it is two layered with the outer mesothelium sitting on a bed of connective tissue.

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12
Q

What are Intra-Peritoneal Organs covered in?

A

These are organs that are totally suspended and that are covered in Serosa. They are lined with a single, thin, squamous layer of mesothelium (visceral peritoneum).

e.g. Stomach, liver, ileum.

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13
Q

What are Retro-Peritoneal Organs covered in?

A

Lined with visceral peritoneum on the anterior surface only and lined with adventitia on the posterior surface.

e.g. Kidneys, ureters, abdominal aorta.

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14
Q

What are “Mixture” organs?

A

Organs that form as Intra-Peritoneal but subsequently become adventitia.

e.g. Pancreas, much of the duodenum.

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15
Q

What is Ascites?

A 
Unusual conditions (e.g. liver disease, heart failure, electrolyte imbalance). 
There is an accumulation of fluid; abdominal swelling  and distortion of visceral organs.
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16
Q

What is Peritonitis?

A

Physical damage, chemical irritation, bacterial invasion (complication from surgery). Inflammation interferes with normal functioning.

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17
Q

What are the responses associated with the Sympathetic Division of the Autonomic Nervous System (ANS)?

A

Exercis.
Emotion.
Excitement.

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18
Q

What does the Sympathetic Division do to the gut functions?

A

It inhibits them. Predominately at times of activity/stress. It diverts blood to brain and muscles.

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19
Q

What are the responses associated with the Parasympathetic Division of the Autonomic Nervous System?

A

Repletion.
Rest.
Relaxation.

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20
Q

What does the Parasympathetic Division do to the gut functions?

A

It promotes them during and after meal times. It stimulates the secretion and transport in the gut tube.

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21
Q

What are the three Salivary glands?

A

Parotid.
Submandibular.
Sublingual.

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22
Q

What does the Parotid secrete?

A

It contributes 25% of Saliva.
It secretes serous secretions only.
Mumps virus is associated with it.

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23
Q

What does the Submandibular secrete?

A

It contributes 70% of Salivia.

It secretes mixed secretions (both serous and mucus).

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24
Q

What does the Sublingual secrete?

A

It contributes to 5% of Saliva.

It secretes mixed secretions (both serous and mucus).

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25
Q

What does a Serous acinus secrete?

A

Serous fluid. Which is watery.

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26
Q

What is the predominant enzyme is a Serous acinus?

A

Amylase (CHO).

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27
Q

What type of granules are in the Serous acinus?

A

Zymogen granules.

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28
Q

What are myoepithelial cells?

A

Cells that are present around mucus acini. They are modified epithelial cells which are contractile; they squeeze acing contents into the lumen.

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29
Q

What do the mitochondria do in the Submandibular gland?

A

They’re metabolically active, so when you increase metabolic activity you increase active transport.

N.B. the mitochondria are aligned.

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30
Q

What type of granules are in the Mucous acinus?

A

Mucous granules.

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31
Q

What are the components of Saliva?

A

99% water.

Assortment of ions, buffers, metabolites and enzymes.

32
Q

What are the three functions of Saliva?

A

Lubrication.
Protection.
Digestion.

33
Q

What component of Saliva aids in lubrication?

A

Carbohydrate-rich glycoproteins (mucins).

34
Q

What else do mucins do?

what function does this belong to?

A

It helps with bacterial adhesion and secretions.

PROTECTION.

35
Q

What do Bicarbonate ions do?

what function does this belong to?

A

Help with bacterial secretion and vomit (acidic).

PROTECTION.

36
Q

What does Lysozyme do?

what function does this belong to?

A

Breaks down bacterial cell wall.

PROTECTION.

37
Q

What does Lactoferrin do?

what function does this belong to?

A

Fight independent bacteria.

PROTECTION.

38
Q

What does Immunoglobulin A do?

what function does this belong to?

A

Fights bacteria and viruses generically.

PROTECTION.

39
Q

What does Amylase do?

what function does this belong to?

A

It aids in digestion. It’s active range pH is 4-11.
Helps digest CHO.

DIGESTION.

40
Q

What does Lipase do?

what function does this belong to?

A

Breakdown fats. The optimal pH is 4.

DIGESTION.

41
Q

What does Kallikrein do?

A

Cleave and activate Bradykinen which will increase the blood supply.

42
Q

What does each salivary gland receive?

A

Parasympathetic and Sympathetic stimulation.

43
Q

What causes an increase in Salivary secretion?

A

Sight and thought of food (preparation, presentation, smell, taste, chewing) and nausea.

44
Q

What causes a decrease in Salivary secretion?

A

Fatigue, sleep, fear, dehydration and exercise.

45
Q

How does the PSNS control Salivary Secretion?

A

It accelerates secretion, this will result in the production of large amounts of watery saliva. The myoepithelial cells contract; and blood flow increases. This will sustain the demand for metabolism.

46
Q

How does the SNS control Salivary Secretion?

A

There is secretion of a small volume of viscous saliva containing high enzyme concentrations. The reduced volume produces the sensation of a dry mouth. Blood vessels are constricted so there is restriction of blood flow and secretion.

47
Q

What causes Xerostomia (dry mouth)?

A
  1. Mumps (virus which preferentially targets the parotid glands).
  2. Salivary duct calculi (stones).
  3. Salivary gland tumours (usually benign).
  4. Sjögren’s syndrome - autoimmune condition (generalised dryness).
  5. Medications.
48
Q

What causes Hypersalivation (water brash)?

A
  1. It is associated with many conditions including peptic ulceration and IBD.
  2. Medications.
  3. Toxins (organophosphates, arsenic).
49
Q

What is Meth Mouth?

A

Methamphetamine use can lead to destruction of salivary glands. This can lead to bad teeth, as you have lost essential functions i.e. protection, ingestion and lubrication.

50
Q

How long is the Oesophagus?

A

The straight tube is 25cm long.

51
Q

What is the function of the Oesophagus?

A

Rapid transport (peristalsis) of food bolus to the stomach.

52
Q

What is the straight tube of the Oesophagus?

A

Long, with thick muscular walls that have protective lining. The outline is collapsed with folds of submucosa when empty; these are stretched out flat as food descends to the stomach.

53
Q

Describe the epithelium of the Oesophagus?

A

There is thick sacrificial stratified squamous (6-8) layers, it is non-keratinised (with a small number of keratohyalin granules present but do not undergo true cornification). The epithelium transitions into simple cuboidal/columnar as it approaches the stomach.

54
Q

Describe the muscular mucosae of the Oesophagus?

A

It is absent rare in the proximal oesophagus but more developed near the stomach. Longitudinal smooth muscle and elastic network (discontinuous in places). It permits independent movement and folding of the mucosa, aiding in digestion and absorption.

55
Q

What glands are present in the Oesophagus?

A
  1. Submucosal mucous glands - these are unevenly distributed and they lubricate the passage.
  2. Oesophageal cardiac glands - these are confined to the lamina propria (in the lower oesophagus). They resemble cardiac glands (in the stomach).
56
Q

What do Oesophageal Cardiac Glands do?

A

The mucus they secrete, protects the epithelium from acid reflux from the stomach (heartburn); however it is not always successful. You can sometimes get ulceration of the inferior oesophagus due to acid attack. As the ulcers heal, the oesophagus may become narrowed due to scarring (Oesophageal stricture) - therefore swallowing is difficult.

57
Q

Describe the Muscularis Externa of the Oesophagus?

A

There are two thick coats: inner and outer. They’re not always circular and longitudinal. Sometimes they are: inner = spiral and oblique bundles, outer = irregularly arranged in many places.

58
Q

Describe the top 1/3 of the Muscularis Externa of the Oesophagus?

A

Skeletal muscle.

59
Q

Describe the middle 1/3 of the Muscularis Externa of the Oesophagus?

A

Mixed skeletal and smooth muscle.

60
Q

Describe the inferior 1/3 of the Muscularis Externa of the Oesophagus?

A

Mostly smooth muscles.

61
Q

Describe the sphincters of the Oesophagus?

A

There are two. Upper and Lower. They are physiological rather than anatomical. There is no obvious muscle thickening. However there is some increase in the inner muscle coat in the lower sphincter area. Tonal contraction occurs.

62
Q

Describer the Adventitia of the Oesophagus?

A

It is covered in adventitia except for the 1-2cm between the diaphragm and the stomach (retroperitoneal; anterior and left lateral surfaces covered by serosa).

63
Q

Describe the nerves of the Oesophagus?

A

Autonomic Nervous System. ANS coordinates movements involved in swallowing.

64
Q

What happens in Peristalsis?

A
  1. INITIAL STATE: the muscle layers are even with each other.
  2. Contraction of circular muscles behind bolus occurs.
  3. Contraction of longitudinal muscles ahead of bolus occurs.
  4. Contraction of circular muscle layer forces bolus forward.
65
Q

Describe Peristalsis in one sentence?

A

It propels materials along the length of the digestive tract by coordinated contractions of the circular and longitudinal layers.

66
Q

Describe Segmentation?

A

Segmentation movements primarily involve the circular muscle layers. These activities churn and mix the contents of the digestive tract, but do not produce net movement in a particular direction.

67
Q

What is Achalasia?

A

Aperistalsis of the oesophagus with a failure of the lower oesophageal sphincter to relax swallowing. It is a gastro-oesophageal disease.

68
Q

What is Gastro-oesophageal disorder (GORD)?

A

Chronic reflux, acid always goes back up into the oesophagus.

69
Q

What is Barrett’s oesophagus?

A

Where the stratified epithelial cells become glandular. It can lead to oesophageal cancer.

70
Q

What are other gastro-oesophageal disease?

A 
Reflux oesophagiti. 
Neurological disorder (brainstem), neuromuscular disorders, extreme old age.  
Oesophageal varices - which are weak veins that can bleed easily.
71
Q

What occurs in the stomach?

A

It acts as a storage tank. Digestion, secretion and sterilisation take place. Some absorption occurs here.

72
Q

How much can the stomach hold?

A

Approximately 1.5L.

73
Q

What are the key regions of the stomach?

A

Cardia.
Fundus.
Body.
Pylorus.

74
Q

What do the parietal (oxyntic) glands release?

A

HCL.
IF - intrinsic factor.
Pepsinogen.
Somatostatin.

75
Q

What do the cardiac glands release?

A

Mucus.

76
Q

What do the pyloric glands release?

A

Pepsinogen.
Mucus.
Gastrin.
Somatostatin.

77
Q

How many layers are in the muscular externa of the stomach?

A

There are 3 (going from out to in):

  1. Outer Longitudinal layer.
  2. Inner Circular layer.
  3. Oblique muscle layer overlying mucosa.

DS (32 decks)

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