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Anatomy and Physiology > The Digestive system > Flashcards

The Digestive system Flashcards

1
Q

what are the 5 stages of digestion

A 
1- Ingestion
2- Digestion
3- Secretion
4- Absorption
5- Excretion
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2
Q

name all the subdivisions in the gastrointestinal tract and in order naming the purpose

A
  • Oral cavity, mechanical processing and saliva break down
  • pharynx, propulsion of food
  • Osophagus, transport channel
  • Stomach, chemical and mechanical breakdown
  • small intestine, enzymatic digestion and absorption
  • Large intestine, enzymatic digestion and absorption
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3
Q

Name the Accessory organs to the gastrointestinal tract

A
  • salivary gland
  • liver
  • gall bladder
  • pancreas
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4
Q

what is the peritoneum

A
  • the peritoneal sac that holds and lines all abdominopelvic organs and cavity, and is a serous membrane
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5
Q

what is a serous membrane

A

a membrane that lines walls and organs of a body cavity and make serous fluid

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6
Q

describe the structure of the peritoneum

A
  • parietal peritoneum lines the cavity
  • visceral peritoneum (serosa) lines the organs
  • mesentery, provides a passageway for nerves, blood vessels and lymphatic vessels to the GI tract
  • peritoneal fluid fills the sac and provides lubrication
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7
Q

what are the 4 layers of the GI tract wall, starting from the inner

A
  • Mucosa
  • Submucosa
  • Muscularis externa
  • Serosa/Visceral peritoneum
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8
Q

Describe the mucosa

A
  • 2 layers
  • Mucosal epithelium, stratified squamous from mouth to oesophagus, simple columnar with mucous cells everywhere else
  • Lamina Propria, areolar tissue with blood vessels, lymph vessels and nerve endings
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9
Q

Describe the submucosa

A
  • summary: dense connective tissue with blood vessels, glands and nerve endings
    1- layer of dense irregular connective tissue
    2- many blood and lymphatic vessels
    3- contains exocrine glands to secrete enzymes into GI tract
    4- Submucosal plexus, the neural network that innervates submucosa and mucosa
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10
Q

Describe the Muscularis Externa

A
  • 2 layers of smooth muscle
  • inner circular layer
  • outer longitudinal layer
  • coordinates by the enteric nervous system and the parasympathetic division
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11
Q

Describe the serosa (Visceral peritoneum)

A
  • serous membrane covering muscularis externa

- this serosa is replaced by Adventitia (dense collagen), in the oesophagus and above aswell as the rectum

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12
Q

How does peristalsis occur?

A
  • this it rhythmic contractions controlled by pacesetter cells
    1- circular muscles behind bolus contract
    2- longitudinal muscles behind bolus contract and repeat
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13
Q

what components make up saliva

A
  • salivary amylase
  • lingual lipase
  • water
  • electrolytes
  • mucins (Glycoproteins that form lubricants)
  • antibodies
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14
Q

what is the function of the oral cavity

A
  • mechanical processing
  • lubrication
  • sensory analysis
  • breakdown
  • passage way
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15
Q

name the 2 salivary glands and their location

A
  • Parotid (back of mouth)
  • Sublingual (in tongue)
  • submandibular (in jaw beneath tongue)
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16
Q

Function of the osophagus

A
  • takes food to the stomach
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17
Q

describe the structure of the osophagus

A

1) Mucosa: 3 layers
- Stratified squamos epithelia
- lamina propria
- muscularis mucosae
2) Sub mucosa
3) Muscularis externa
4) Adventitia (dense collagen)

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18
Q

Describe the phases of swallowing

A

1) Buccal phase: Tongue pushes bolus to back of mouth
2) pharyngeal phase: epiglottis folds over and food enters pharynx
3) oesophageal phase: bolus moves down oesophagus by peristalsis into stomach

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19
Q

What occurs in the stomach

A
  • chemical and mechanical digestion

- food storage

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20
Q

Describe everything about the enzymes, acid and intrinsic factors found in the stomach

A
  • Enzymes; Pepsin to break down proteins, salivary amylase and ligual lipase
  • HCl acid, pH 2 destroys pathogens
  • Stomach produces intrinsic factor, which helps the body absorb Vitamin B12
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21
Q

what us the name of the exit of the stomach

A
  • Pylorus

- controlled by the pyloric sphincter

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22
Q

Describe the stomach lining and how it differs from the rest if the GI tract

A
  • 4 normal layers, mucosa, submucosa, muscularis externa and serosa
  • mucosa; simple columnar epithelia, produces mucous, has openings called gastric pits which lead to gastric glands, cells are constantly being replaced
  • Muscularis externa; has an additional layer called oblique muscle as well as the normal circular and longitudinal
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23
Q

Describe the structure of gastric glands

A
  • opening called gastric pit
  • splits into the glands
  • glands contain special epithelial cells;
    Parietal cells and chief cells in the walls and G-cells in the very bottom epithelia
24
Q

what are the functions of the 3 cell types in gastric glands

A
  • Parietal: to secrete intrinsic factor and HCl
  • Chief cells: secrete pepsinogen, the precursor to pepsin and reacts with HCl to make pepsin
  • G-cells: secrete gastrin and a stomach hormone
25
Q

Function of pyloric glands

A
  • found in pylorus, the stomach exit
  • produce mucous
  • secrete gastrin by G-cells
  • D-cells secrete somatostatin which inhibits gastrin
26
Q

How do parietal cells secrete HCl yet not get burned themselves by the acid

A
  • Within parietal cells, CO2 dissolves into H20 due to the enzyme carbonic anhydrase, produces H2CO3
  • H2CO3 is split into H+ and HCO3- ions
  • HCO3- is exchanged for Cl- from the blood via a protein
  • H+ and Cl- are transported out the parietal cell separately through different specific proteins into the gastric gland
27
Q

What are the 3 phases that stimulate and regulate gastric activity (production of gastric juices)

A

1) Cephalic phase: stimulus like smell, sight or taste of food triggers CNS to stimulate gastric glands
2) Gastric phase: stretching of the stomach walls due to entering of food triggers the stomach reflex, increasing mechanical digestion and more HCl seceretion
3) Intestinal phase: Food leaves through pylorus, receptors in the intestine are stimulated releasing hormones which inhibit the stomach to stop releasing HCl and enzymes

28
Q

What methods or mechanisms does the stomach employ to ensure it isn’t harmed by the acids and enzymes

A
  • Thick mucous layer
  • Rapid cell division of epithelia
  • parietal cells secrete H+ and Cl- separately
  • inhibitory hormones from small intestine (CCK,GIP, secretin) reduce production
  • pepsinogen is an inactive precursor, only becomes damaging when pepsin
29
Q

what are the 3 regions of the small intestine with length

A

1- Duodenum 25cm
2- Jejunum 2.5m
3- Ileum 3.5m

30
Q

function of the duodenum

A
  • receives secretions of enzymes from the pancreas and liver, neutralisation of acidic chime occurs
31
Q

function of the jejunum and ileum

A

jejunum - location of the majority of nutrient absorption, and chemical digestion, huge surface area due to microvilli and folds
Ileum - More absorption, has lymphoid nodules to produce immune cells

32
Q

what structures are found in the intestinal wall

A
  • lacteal
  • villi with microvilli
  • intestinal crypts (deeper voids)
33
Q

Describe a villus

A
  • outer layer of simple columnar epithelium with microvilli, and occasionally mucous cells
  • a capillary network
  • a lacteal
34
Q

What are brush border enzymes and what do they secrete

A
  • these are enzymes bound to the membrane of epithelial cells with microvilli, which break down substances that come in contact
  • these membrane bound proteins also produce enteropeptidase which activates trypsinogen to convert to trypsin
35
Q

what are enteroendocrine cells

A
  • cells in intestinal glands that produce hormones, gastrin, CCK and secretin
36
Q

what do duodenal glands produce?

A
  • mucous, which is slightly alkaline to raise the pH
37
Q

what is the purpose of intestinal juice

A
  • To keep everything liquid and buffer acids
38
Q

The pancreas secretes pancreatic juice, which is made up of what?

A
  • Pancreatic alpha amylase
  • Pancreatic lipase
  • nucleases (break down nucleic acids)
  • proteases and peptidases (only activate when reach the duodenum)
39
Q

Where are pancreatic juices made and secreted specifically?

A
  • made by exocrine cells in the pancreatic acini

- juice is secreted into the pancreatic duct

40
Q

Describe the livers blood supply

A
  • 1/3 of the blood is from hepatic artery

- 2/3 of blood is from the heptic portal vein

41
Q

where does the hepatic portal vein come from?

A
  • a network of capillaries from the digestive tract

- the blood is filled with nutrients

42
Q

what is the function of the liver?

A
  • To filter the blood from the hepatic portal vein, extracting all the nutrients before it goes to the heart
43
Q

Describe all the features of the hexagonal subunits that make up the liver

A
  • in each corners of the hexagonal subunit (lobule) is a portal area
  • there are 3 different portal areas: branch of hepatic portal vein, branch of hepatic artery, branch of bile duct
44
Q

What cell type produces bile and where does it go

A
  • Hepatocytes (liver cells) produce bile and it is absorbed into the bile ducts
45
Q

In what ways does the liver regulate metabolic activities

A
  • metabolism of carbs lipids and amino acids
  • waste product removal (NH3 and toxins)
  • vitamin storage (B12)
  • mineral storage (Ferritin)
  • drug inactivation
46
Q

in what ways does the liver regulate blood contents

A
  • liver regulates synthesis of blood plasma
  • regulates phagocytosis and antigen presentation
  • removal of circulating hormones, antibodies and toxins
47
Q

where is bile stored and released

A
  • stored in the gall bladder

- released into the duodenum

48
Q

what hormone stimulates the release of bile and how does it work

A
  • hormone CCK causes the hepatopancreatic sphincter to release and gall bladder to contract pushing bile out
49
Q

how does bile increase lipid break down

A

– bile breaks down insoluble lipid droplets by emulsification

50
Q

what hormone is released from the stomach and its function

A
  • gastrin

- stimulates acid production and stomach contractions

51
Q

which hormones are released from the small intestine and their function

A
  • GIP - releases insulin from pancreas, and inhibits gastrin
  • Secretin and CCK - release of pancreatic enzymes, buffer and bile
  • VIP - dilation of intestinal capilleries
52
Q

What is the name of the valve dividing the small and large intestine

A
  • Ileocecal valve
53
Q

Name the 4 sections of the large intestine in order

A
  • Ascending colon
  • Transverse colon
  • Descending colon
  • Sigmoid colon
54
Q

what is the function behind the large intestine

A
  • some absorption occurs
  • reabsorption of water and bile salts
  • absorption of vitamins and organic waste
  • site of bacterial vitamin production
  • compaction and storage of faeces
55
Q

Describe the structure of the large intestine wall

A
  • no villi and microvilli
  • more mucous cells to secrete mucous for lubrication as most water has been absorbed
  • only 2 thin muscle layers in the muscularis externa

Anatomy and Physiology (16 decks)

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