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HUBS192 > Lecture 20- The basic structure of the GI system > Flashcards

Lecture 20- The basic structure of the GI system Flashcards

1
Q

What is the primary function of the GI system?

A

Bring nutrients into the internal environment so

that they can be used. What is not needed is excreted as waste.

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2
Q

What are the four functions of the GI system?

A
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
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3
Q

What are the two types of digestion? What does digestion allow?

A
  • Mechanical digestion= physically breaking things down into smaller parts to increase surface area
  • Chemical digestion= involves use of enzymes

Breaking things down then means they are small enough to be absorbed

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4
Q

What things does the GI secret?

A
  • Mucus (protection)
  • Serous fluid (lubrication)
  • Acid +enzymes (for chemical digestion)
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5
Q

What’s the start of the GI tract? What’s the end?

A

Spans from the mouth to the anus

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6
Q

Describe the path of the GI tract from the mouth to the anus highlighting the key structures as you go down…

A
  • Ingest food goes into oral cavity
  • Chew + swallow
  • Oropharynx + larynx pharynx
  • Esophagus
  • Stomach, stored for mechanically + chemical digestion
  • Small intestine (nutrient absorption)
  • Empty into large intestine (water + electrolyte absorption)
  • Left over is feces excreted by rectum and anus
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7
Q

What are sphincters and what are their role in the GI tract?

A
  • Thickened regions of circular smooth muscle.

- Partition GI tract into multiple functional compartments

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8
Q

What is the GI tract lined with and why?

A

Epithelium as is in contact with the outside world

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9
Q

What can the GI tract be described as?

A

Long tube with outgrowths

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10
Q

What are outgrowths?

A

Accessory organs, empty into tubular GI tract via a duct system

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11
Q

What are microvilli?

A
  • They are shorter than cilia

- Finger like extensions of plasma membrane that help to increase surface area in the GI tract

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12
Q

What type of epithelium is found in the mouth/oral cavity and esophagus? Why?

A
  • Stratified squamous

- Lots of layers means protection from abrasion which is required due to food and drink passing through

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13
Q

What type of epithelium is found in the Stomach, Small Intestine and Large Intestine? Why?

A
  • Simple Columnar

- Tall cells means can fit a lot more secretory organs. These areas need to be specialized for secretion and absorption.

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14
Q

What type of epithelium is found in the anal cavity? Why?

A
  • Stratified Squamous

- Need protection from abrasion due to feces

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15
Q

What is a unicellular gland? What is an example?

A
  • Simplest type of gland as only consists of one cell

- Only example in human body is the goblet cell

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16
Q

What are the features of a goblet cell?

A
  • Columnar
  • Goblet shape (take on this shape as packed full)
  • Apical mucous granules
  • Basal nucleus (packing pushing nucleus towards the basement membrane)
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17
Q

How can you tell where a goblet cell is on a histological slide?

A
  • Goblet shape

- Don’t pick up stain well so often white in colour compared to surrounding tissue

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18
Q

What are the two types of multicellular glands?

A

Multicellular glands are made of more than one cell:

  • Simple: gland with single duct (e.g. stomach and small intestine)
  • Compound: gland with 2 or more ducts (e.g. salivary glands)
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19
Q

Order from most surface area for secretion to the least….
Simple multicellular gland
Unicellular gland
Compound multicellular gland

A

Compound multicellular gland
Simple multicellular gland
Unicellular gland

20
Q

What are the four layers of the gut tube going from the lumen outwards?

A
  1. Mucosa
  2. Submucosa
  3. Muscularis (externa/proper)
  4. Adventitia
21
Q

What is the general role of the mucosa? What does it consist of?

A

-Is the mucus membrane

  • Consists of:
    1. Epithelium sitting on a basement membrane
    2. Lamina propria (FCT)
    3. Muscularis Mucosae
22
Q

What is the Muscularis Mucosae? Is it the same as the

Muscularis (externa/proper)?

A
  • Layer of smooth muscle associated with the mucosa

- No it is not the same as the Muscularis externa/proper which is a layer of the gut tube in its own right

23
Q

What is the submucosa? What does it contain?

A

-Is the layer of connective tissue (elastin +collagen) below the Mucosa

  • Contains:
    1. Glands
    2. Blood vessels
24
Q

How is secretion of glands in the submucosa regulated?

A

-It is the Muscularis Mucosae (smooth muscle layer in the mucus membrane) that contracts to squeeze the glands
-Secretion is regulated by the submucosal nerve
plexus, part of the enteric nervous system (ENS)

25
Q

What is the enteric nervous system?

A

The gut has a local nervous system acting independently from the central nervous system

26
Q

What is the Muscularis proper/ externa? What are the 2 main layers?

A

-Is the smooth muscle layer of the gut tube

  • 2 layers of muscle are:
    1. Inner circular (good at controlling the tubes diameter by contracting and relaxing)
    2. Outer longitudinal (good at shortening the tube)
27
Q

What is the myenteric plexus?

A
  • Part of Enteric Nervous System (ENS)
  • Is in between the muscle layers of the Muscularis proper/externa
  • Regulates motility
28
Q

What is the role of the adventitia?

A
  • The adventitia is the outermost layer of the gut tube
  • Made of FCT
  • In some cases helps adhere the tube to surrounding structures
29
Q

What happens to the gut tube when organs are in the peritoneal cavity?

A

There is an additional outer covering called the serosa (not considered one of the four layers)

30
Q

What is the peritoneum?

A
  • A serous membrane
  • Consists of two layers:
    1. Parietal layer: lines the body wall
    2. Visceral layer: lines the organs
  • Between these layers is a fluid filled space
31
Q

What does the space/ cavity within the peritoneum allow?

A

It should be viewed as more like potential space and as is filled with fluid allows for frictionless movement of muscles inside

32
Q

What does Retroperitoneal mean?

A
  • Posterior to the peritoneum
  • Some organs don’t need to move around, such as the pancreas. These therefore do not sit inside the peritoneum and instead are anchored to the posterior abdominal wall. They will still however have visceral peritoneum covering their anterior side.
33
Q

What is the basic function of the pancreas?

A

Important source of digestive enzymes which are secreted into the small intestine.

34
Q

What is a Mesentery?

A

Double layer of visceral peritoneum that connects/ anchors organ to body wall preventing tubular sections from becoming tangled in knots

35
Q

What is Omenta?

A

Double layer of visceral peritoneum that connects an

organ to another organ

36
Q

What features of the small intestine will be seen in the next lab?

A
  • Slippery/ shiny surface due to the visceral peritoneum
  • Contains vessels (arteries, nerves, veins lymphatics)
  • May also be able to see adipose tissues
  • Wall of the small intestine is very thin
37
Q

What are the boundaries of the mouth/ oral cavity?

A
  • Superior= hard +soft palate
  • Inferior= tongue
  • Lateral= cheeks
38
Q

What does the mouth do in regards to food?

A
  • Chemical digestion begins via enzymes
  • Mechanical digestion via chewing
  • Lubrication
  • Forms the bolus which when swallowed goes through the fauces into the oropharynx then into the esophagus
39
Q

What are the 3 pairs of salivary glands and where are they connected to?

A
  • 3 pairs:
    1. Parotid - Serous fluid with amylase
    2. Sublingual – Mucous only
    3. Submandibular – Mixed

-Connected to the oral cavity and in total secret 1L per day

40
Q

What is the structure of Salivary Glands?

A
  • Compound secretory glands

- Cells in clusters = acinus

41
Q

In salivary glands what do acinar cells secrete?

What do duct cells secrete?

A
  • Acinar cells secrete enzymes (amylase)

- Duct cells secrete bicarbonate (buffering)

42
Q

What is the esophagus and where is it located?

A
  • Long tube (~25cm)
  • Located posterior to the Trachea
  • Extends from the pharynx to the stomach
  • Basic function is to create a passage for the food
43
Q

What does the epiglottis do?

A

-Epiglottis ensures that food enters the esophagus, and

not the trachea

44
Q

How are the layers of the tube modified in the esophagus to specialize for the passing of food?

A
  • Highly folded submucosa and mucosa means there is the capacity to expand
  • Mucosa: stratified squamous epithelium (protection from abrasion due to layers)
  • Muscularis externa: Move food bolus
45
Q

How does the Muscularis externa layer of the esophagus change as you move down?

A
  • First 1/3: skeletal muscle (as voluntary control)
  • Middle 1/3: a mixture (transition area)
  • Last 1/3: smooth muscle (as involuntary control)
46
Q

Are there goblet cells in the esophagus?

A
  • Goblet cells are tall columnar cells so wouldn’t fit in stratified squamous. Also likely to be knocked off by abrasion from food.
  • Therefore, instead of having goblet cells in the epithelium there are glands in the submucosa with ducts carrying the mucus to the surface. This is important as the esophagus needs mucus for lubrication and protection.

HUBS192 (38 decks)

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