The Digestive system Flashcards
1
Q
what are the 5 stages of digestion
A
1- Ingestion 2- Digestion 3- Secretion 4- Absorption 5- Excretion
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
3
Q
Name the Accessory organs to the gastrointestinal tract
A
- salivary gland
- liver
- gall bladder
- pancreas
4
Q
what is the peritoneum
A
- the peritoneal sac that holds and lines all abdominopelvic organs and cavity, and is a serous membrane
5
Q
what is a serous membrane
A
a membrane that lines walls and organs of a body cavity and make serous fluid
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
7
Q
what are the 4 layers of the GI tract wall, starting from the inner
A
- Mucosa
- Submucosa
- Muscularis externa
- Serosa/Visceral peritoneum
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
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
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
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
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
13
Q
what components make up saliva
A
- salivary amylase
- lingual lipase
- water
- electrolytes
- mucins (Glycoproteins that form lubricants)
- antibodies
14
Q
what is the function of the oral cavity
A
- mechanical processing
- lubrication
- sensory analysis
- breakdown
- passage way
15
Q
name the 2 salivary glands and their location
A
- Parotid (back of mouth)
- Sublingual (in tongue)
- submandibular (in jaw beneath tongue)
16
Q
Function of the osophagus
A
- takes food to the stomach
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)
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
19
Q
What occurs in the stomach
A
- chemical and mechanical digestion
- food storage
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
21
Q
what us the name of the exit of the stomach
A
- Pylorus
- controlled by the pyloric sphincter
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
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
Function of pyloric glands
- found in pylorus, the stomach exit
- produce mucous
- secrete gastrin by G-cells
- D-cells secrete somatostatin which inhibits gastrin
26
How do parietal cells secrete HCl yet not get burned themselves by the acid
- 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
What are the 3 phases that stimulate and regulate gastric activity (production of gastric juices)
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
What methods or mechanisms does the stomach employ to ensure it isn't harmed by the acids and enzymes
- 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
what are the 3 regions of the small intestine with length
1- Duodenum 25cm
2- Jejunum 2.5m
3- Ileum 3.5m
30
function of the duodenum
- receives secretions of enzymes from the pancreas and liver, neutralisation of acidic chime occurs
31
function of the jejunum and ileum
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
what structures are found in the intestinal wall
- lacteal
- villi with microvilli
- intestinal crypts (deeper voids)
33
Describe a villus
- outer layer of simple columnar epithelium with microvilli, and occasionally mucous cells
- a capillary network
- a lacteal
34
What are brush border enzymes and what do they secrete
- 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
what are enteroendocrine cells
- cells in intestinal glands that produce hormones, gastrin, CCK and secretin
36
what do duodenal glands produce?
- mucous, which is slightly alkaline to raise the pH
37
what is the purpose of intestinal juice
- To keep everything liquid and buffer acids
38
The pancreas secretes pancreatic juice, which is made up of what?
- Pancreatic alpha amylase
- Pancreatic lipase
- nucleases (break down nucleic acids)
- proteases and peptidases (only activate when reach the duodenum)
39
Where are pancreatic juices made and secreted specifically?
- made by exocrine cells in the pancreatic acini
| - juice is secreted into the pancreatic duct
40
Describe the livers blood supply
- 1/3 of the blood is from hepatic artery
| - 2/3 of blood is from the heptic portal vein
41
where does the hepatic portal vein come from?
- a network of capillaries from the digestive tract
| - the blood is filled with nutrients
42
what is the function of the liver?
- To filter the blood from the hepatic portal vein, extracting all the nutrients before it goes to the heart
43
Describe all the features of the hexagonal subunits that make up the liver
- 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
What cell type produces bile and where does it go
- Hepatocytes (liver cells) produce bile and it is absorbed into the bile ducts
45
In what ways does the liver regulate metabolic activities
- metabolism of carbs lipids and amino acids
- waste product removal (NH3 and toxins)
- vitamin storage (B12)
- mineral storage (Ferritin)
- drug inactivation
46
in what ways does the liver regulate blood contents
- liver regulates synthesis of blood plasma
- regulates phagocytosis and antigen presentation
- removal of circulating hormones, antibodies and toxins
47
where is bile stored and released
- stored in the gall bladder
| - released into the duodenum
48
what hormone stimulates the release of bile and how does it work
- hormone CCK causes the hepatopancreatic sphincter to release and gall bladder to contract pushing bile out
49
how does bile increase lipid break down
-- bile breaks down insoluble lipid droplets by emulsification
50
what hormone is released from the stomach and its function
- gastrin
| - stimulates acid production and stomach contractions
51
which hormones are released from the small intestine and their function
- GIP - releases insulin from pancreas, and inhibits gastrin
- Secretin and CCK - release of pancreatic enzymes, buffer and bile
- VIP - dilation of intestinal capilleries
52
What is the name of the valve dividing the small and large intestine
- Ileocecal valve
53
Name the 4 sections of the large intestine in order
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
54
what is the function behind the large intestine
- 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
Describe the structure of the large intestine wall
- 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
