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Digestive System > Anatomy > Flashcards

Anatomy Flashcards

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1
Q

What % of the immune system is distributed by the digestive system

A

70%!

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2
Q

What are the 4 layers of the GIT

A

Contains the same basic 4-layer arrangement of tissues

  1. Mucosa -
    - Mucosal epithelium
    - lamina propria
    - muscularis mucosa
  2. Submucosa
  3. Muscularis
  4. Serosa (peritoneum)
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3
Q

What are the three layers of the mucosa layer of the GIT tract

A
  1. Microvilli - large surface area for absorption
  2. Goblet cells - secrete mucous
  3. Enteroendocrine cells - specialised cells secrete hormones into blood
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4
Q

What epithelium do the stomach & intestines contain

A

Contain epithelium for protection

Epithelial cells renew every 5-7 days Columnar epithelium is designed more for absorption

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5
Q

What is found in the lamina propria

A

The second mucosa layer of the GIT tract
It consists of connective tissue containing many blood & lymphatic vessels that allows the absorption of nutrients

Contains GALT (gut associated lymphoid tissue) which are collections of immune cells e.g lymphocytes & macrophages - 70% of body’s immune cells

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6
Q

What makes up the muscularis mucosa layer of the GIT tract

A

Very thin layer of smooth muscle
Layer of muscle creates the villi (small folds) which increase the surface area for absorption & digestion
Movement of this ensures all absorptive cells are fully exposed to the GIT contents

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7
Q

What makes up the submucosa layer of the GIT tract

A

Contains blood & lymph vessels which receive absorbed food molecules
Contains network of neurons called the ‘submucosal plexus’ -brain of the gut
May contain glands & lymphatic tissue

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8
Q

What makes up the muscularis externa layer of the GIT tract

A

Mouth, pharynx, upper oesophagus & anal sphincter contain skeletal muscle to allow voluntary swallowing
Rest of the GIT is mostly smooth muscle, involuntary, with two layers
- inner circular muscle
- Outer longitudinal

Involuntary smooth muscle contraction aids
Mixing of food with digestive juices
Propelling food along the digestive tract

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9
Q

Functions of the peritoneum

A

Weaves between digestive organs and supplies many blood & lymph vessels
Provides a physical barrier to protect against local infections

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10
Q

What is the greater omentum

A

Omentum = latin for apron

Largest fold of the peritoneum
Drapes over transverse colon & small intestine
Its a double sheet that folds back on itself, hence 4 layers
Stores fat - contains adipose tissue which can greatly expand with weight gain (‘beer belly’)
Has many lymph nodes containing macrophages & plasma cells (which produce antibodies) to combat infections of the GIT

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11
Q

What is the lesser omentum

A

A peritoneal fold that suspends the stomach & duodenum (first part of small intestine) from the liver

Provides a pathway for blood vessels entering the liver
Contains the hepatic portal vein, common hepatic artery, common bile duct & lymph nodes

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12
Q

What is the enteric nervous system

A

The ‘brain’ of the gut that extends from the oesophagus to the anus
Contains 100 million neurons (more than spinal cord)
Functions independently but is regulated by the autonomic nervous system
Parasympathetic (main nerve is vagus) = increase in myentric plexus & submucosal plexus

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13
Q

What 3 types of neurons are found in the enteric nervous system

A
  1. Motor neurons (outgoing/action signal) - in the myenteric plexus controls peristalsis & in the submucosal plexus controls secretions
  2. Sensory neurons (incoming signal) - receive information about the mucosal environment: chemoreceptors & stretch receptors
  3. Interneurons - connect the two plexuses
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14
Q

What supplies the GIT tract with oxygenated blood

A

Arterial blood from branches of the abdominal aorta is supplied via the mesenteric arteries

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15
Q

How does the portal system transfer blood to the body

A

Nutrient rich blood is returned by veins via the liver

The liver filters the blood & processes nutrients which then enter systemic circulation

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16
Q

What is the role of the portal vein

A

Drains the lower oesophagus, stomach, pancreas, small & large intestine, upper rectum & spleen

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17
Q

What is the role of the iliac veins

A

Drain the lower part of the rectum & anal canal

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18
Q

What are the roles of the hard & soft palates of the oral cavity

A

Hard = bony partition between oral & nasal cavity which allow simultaneous chewing & breathing

Soft = arch of muscle

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19
Q

What is the uvula of the oral cavity

A

Dangly thing - latin for ‘small bunch of grapes’

It swings up & blocks the nasopharynx preventing food from entering the nasal cavity

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20
Q

What type of muscle is the tongue

A

Skeletal muscle as it is voluntary to move

Attached to the hyoid bone & mandible

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21
Q

What are papillae

A

Small bumps found on superior surface of the tongue that contain taste buds

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22
Q

What is dentin

A

Teeth are structured as a crown, neck & root
Dentin makes up the bulk of a tooth internally
Teeth are covered externally by mineral rich enamel

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23
Q

What are the gingiva & periodontal membrane

A

Gingiva are our gums

The periodontal membrane is a ligament that fixes to bone/connects teeth

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24
Q

Where is saliva produced & how is it controlled

Study These Flashcards
A

Produced by the parotid glands, submandibular glands & sublingual glands via a reflex controlled by the autonomic nervous system
The parasympathetic nervous system stimulates continuous salivation (1-1.5L/day)

25
What lines the oesophagus
Squamous epithelium for protection & lubricated with mucous | Skeletal muscle at top, smooth at bottom
26
What is the epiglottis
A flap of elastic cartilage which prevents food entering the trachea
27
What is the lower oesophageal sphincter
A seal on the stomach that prevents reflux of its contents into the oesophagus
28
What is the importance of the mucosal stomach lining
Stomach secretes 2-3L of highly acidic (pH 2-3) gastric juice & mucous a day The mucous produced by goblet cells in the stomach provide a ‘barrier’ against the acidity within the stomach Stomach Also contains simple columnar epithelial cells which replace the lining every 3 days
29
What are the 4 main areas of the stomach
1. Cardia - & sphincter 2. Fundus 3. Body 4. Plyorus - & sphincter
30
What are the 3 main exocrine cells found in the stomach & what do they secrete
1. Parietal cells - intrinsic factor & hydrochloric acid 2. Chief cells - pepsinogen & gastric lipase (protein & lipid digestion) 3. Goblet cells - secrete mucous for lining protection
31
How does the pancreas assist in digestion
Releases exocrine & endocrine hormones & enzymes into the lumen of the duodenum
32
What are protease enzymes
Protein digesting enzymes
33
What are the inactive enzymes that the pancreas releases
Trypsin & chymotrypsin for protein digestion Ribonuclease & deoxyribonuclease for dna/rna digestion Lipase for fat digestion Pancreatic amylase breaks down starches into sugars
34
What are the main components of the Digestive system
``` Mouth Pharynx Oesophagus Stomach Small intestine Large intestine (including rectum & anal canal) ```
35
What are the main accessory organs of the digestive system
Salivary glands Pancreas Liver Gall bladder & biliary tract
36
Main Functions of the gallbladder
Collects and stores bile & then ejects it down the common bile duct into the duodenum
37
What are the main functions of bile
Helps to digest fats & remove excess cholesterol & other waste products/toxins removed from the liver It is composed of bile salts, cholesterol & bilirubin
38
Where is bile produced
By hepatocytes in the liver | Carried from the hepatic ducts into the gallbladder via the cystic duct
39
What is the ampulla of vater
Where the pancreatic duct (which carries pancreatic enzymes) & the common bile duct meet to form the final small duct pathway that excretes into the duodenum
40
What are the three main regions of the small intestine
1. Duodenum - emulsification & most digestion occurs (30cm) 2. Jejunum - most absorption occurs (2.5m) 3. Illeum - vitamin absorption ie B12 (3.5m)
41
What are villi
Finger like projections with blood capillaries & lacteals (lymphatic capillaries) Absorbed nutrients enter the blood & fatty acids enter the lymph
42
What are microvilli
Micro-folds along the edge of villi Contain brush border enzymes which act as transmembrane proteins - projections of absorptive cell membranes Enzymes are attached to the intestinal lining & include maltase, sucrase, lactase - breaking down double bond sugars
43
What do the brush border enzymes maltase, sucrase & lactase help absorb
Break down sugars & lactose into glucose, fructose, galactose etc
44
What do the brush border enzymes dipeptidase help absorb
Break down proteins into amino acids
45
What do the brush border enzymes nucleosidases & phosphatases help absorb
Digest RNA & DNA
46
What are the main functions of the peptide hormone cholecystokinin (cck)
Released in response to high fat or protein chyme entering duodenum - Stimulates pancreas to release enzymes for digestion - increases hepatic production of bile & gallbladder contraction - mediates satiety
47
What are the main functions of the small intestine
``` Movement/peristalsis of food Digestion Absorption of nutrients & water Hunger/sateity Immunity ```
48
How is water absorbed in the GIT tract
Occurs via osmosis from the lumen into absorptive cells & into blood capillaries, predominantly in the small intestine Absorption of water depends on electrolyte, monosaccharide & amino acid levels to maintain an osmotic balance / concentration gradient with the blood
49
What functions occur in the large intestine
Final stages of digestion, absorption, some vitamin synthesis (through bacterial activity) & stool formation occurs Mucous is produced but no enzymes Absorption of water, minerals, vitamins & some drugs
50
What is the ileocaecal valve
A valve at the end of the small intestine & start of the large intestine which acts as a one way flow valve
51
What are the 4 main regions of the large intestine
1. Caecum - appendix is attached which acts as part of our immune system, mainly in childhood, containing macrophages, lymphocytes etc 2. Colon - ascending, transverse & descending regions 3. Rectum 4. Anal canal - mucous membrane folds, contains an internal & external anal sphincter
52
What are the functions of the microbes found in our large intestine
Rich community of symbiosis, around 100 trillion - Mixture of anaerobic & aerobic bacteria, generally acid producing - Help with final stages of nutrient extraction occuring in the colon through microbial fermentation - Help prevent leaky gut by feeding epthitheleal layers of gut by fermenting fibres to produce short chain fatty acids - can produce vitamin b12 & k
53
What are some key functions of the liver
``` Cleansing blood of microbes Detoxification Bile production & secretion Haemolysis Synthesis of plasma proteins (blood clotting & coagulation factors) Hormone homeostasis Metabolism of glucose, fats & amino acids Heat production Synthesis of vitamins A, D Storage of vitamins ```
54
How & why are lipophilic compounds detoxified by the liver
Lipophilic compounds must be chemically altered into hydrophilic compounds to facilitate elimination Phase 1: bio-activation Activated into more reactive Involves CYP450 family of enzymes (more than 50 types) to metabolise toxins & medications - usually manufactured on the spot Converts water insoluble toxins to be excreted Phase 2: conjugation reactions Molecules attach to toxins to neutralise & make them stable & water-soluble
55
Why do we need dietary lipids
Energy, insulation, cell membranes, hormone production, protection of organs
56
What is the structure of proteins
Long molecules of amino acids, making up 15% of total body mass Amino acid chains create a 3D structure of each protein, which is essential for them to function. Body temp regulation allows proteins to keep their 3D shape Proteins must first be denatured before protease enzymes are able to break them down Amino acids are absorbed in the small intestine
57
What are the main functions of proteins
``` Immunity (antibodies, immunoglobulins) Structures (muscles, collagen) Enzymes Hormones Neurotransmitters Energy ```
58
What are the risks of denaturing protein molecules
PH and temperature
59
What is the process of nutrient absorption in the small intestine
1. Emulsified by bile 2. Enter intestinal cells by diffusion 3. Packaged into chylomicrons which are absorbed into lacteals 4. Travel through the lymph system & enter the blood in the subclavian vein

Digestive System (3 decks)

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