Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Physiology > GI System > Flashcards

GI System Flashcards

1
Q

Ingestion =

A

Eating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Peristalsis =

A

Moving food

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Digestion =

A

Chemical or mechanical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Absorption =

A

Transfer to cardiovascular or lymphatic systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Defecation =

A

Elimination of indigestible material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Digestive organs - gastrointestinal tract

A

Mouth and pharynx
Oesophagus and stomach
Small intestine (duodenum, jejunum, ileum)
Large intestine (colon, rectum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Digestive organs - accessorie organs

A

Teeth and tongue

Salivary glands, liver, gallbladder, pancreas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Mucosa

A

Epithelial layer and connective tissues
Capillaries, enteric neurons, immune cells
Surface area greatly increased by villi/glands

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Submucosa

A

Loose conective tissues and large blood vessels

Contains glands for secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Muscle layer

A

Two layers
Circular/longitudinal
Enteric nervous system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Serosa

A

Connective tissue

Squamous epithelia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Regulation of salivary secretion

A

Modulated by ANS

Parasympathetic-
Watery saliva
Rich in amylase and mucous

Sympathetic-
Promotes output of amylase
Reduces blood flow to glands
Overall effects a reduction in secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Swallowing, voluntary stage

A

Tongue pushes bolus backwards to ortho-pharynx

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Swallowing - pharyngeal stage

A

Reflex action controlled by deglutition Centre in Medulla and Pons of CNS
Soft palate and uvula move up to seal off nasopharynx
Larynx is raised and epiglottis covers and seals glottis, breathing suspended for 1-2 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Swallowing- oesophageal phase

A

Mucous produced to aid swallowing
Food pushed along by peristalsis controlled by medulla of the brain and autonomic nerves
Lower oesophageal sphincter relaxes to allow food to enter stomach
Passage of bolus takes 4-8 seconds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Oesophagus

A

Tube connecting to stomach
Muscularis layer is striated for first third to assist swallowing
Middle third is mixture of striated and smooth muscle
Lower third is all smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Contractile activity in GI tract

A

Segmentation - Occurs largely in the small intestine to facilitate mixing of food
Peristalsis- concerned mainly with propulsion of food along tract

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Hormonal regulation of the GI tract

A

Around 20 different regulatory peptides act through endocrine/paracrine pathways
Endocrine (hormonal) peptides (eg gastrin) regulate secretions in stomach and pancreas
Paracrine (local) agents (eg histamine) regulate secretion in salivary glands and stomach

19
Q

Extrinsic innervation

A

Nerve plexuses linked to CNS via afferent fibres activated by -

  • stretch
  • chemical stimulation

Receive efferent innervation from the ANS

  • Parasympathetic input stimulates gut motility and secretion activity
  • sympathetic nerves cause presynaptic inhibition of parasympathetic-induced contraction
20
Q

Innervation of the GI tract

A

Enteric nervous system

  • found within the wall of the GI tract from oesophagus to anus
  • myenteric (auerbach’s) plexus largely motor in function
  • submucosal (meissner’s) plexus largely sensory, receiving signals from epithelium and stretch receptors
  • release range of substances
    • cholecystokinin (CCK), substance P
    • VIP, somatostatin, enkephalins
21
Q

Functions of the stomach

A

Temporary storage of food
Chemical digestion of proteins
Mechanical digestion by stomach movements
Regulation of passage of chyme into small intestine
Secretion of intrinsic factor - essential for absorption of B¹²

22
Q

Structure of the stomach

A 
Esophagus 
Fundus
Internal folds - rugae 
Body
Greater curvature 
Lesser curvature 
Pyloric antrum 
Pyloric sphincter
Duodenum
23
Q

Gastric glands

A
  • Stomach mucosa composed of epithelium containing many openings (pits/glands)
  • 4 types of cells that together produce gastric juices:
  • chief or peptic or zymogenic secrete pepsinogen
  • parietal or oxyntic cells secrete HCl and intrinsic factor
  • Goblet cells secrete mucous
  • enteroendocrine (G-cells) gastrin, VIP, GIP, CCK…
24
Q

Digestion in the stomach

Mechanical -

A

Three layers of Muscularis enables food to be churned
Food mixed with gastric juices to produce chyme
Chyme passes through Pyloric sphincter to duodenum

25
Digestion in the stomach | Chemical -
Proteins broken down by pepsin (only active in acid environments) Converted from pepsinogen by HALIFAX Mucous protects stomach cells from gastric juices Gastric lipase (also from chief cells) breaks down fat at higher pH (5-6)
26
Phases of gastric secretion
* cephalic phase - stimulated by sight, smell, taste, thought of food or low blood glucose * gastric phase - stimulated by stomach distension due to presence of food * intestinal phase - stimulated by digested proteins in the duodenum
27
Gastrin and control of acid secretion
ECL: Entero Chromaffin-Like cells D-cells: release 5-HT/somatostatin SSR = Somatostatin (5-HT) receptor G-Cells : release gastrin in pyloric antrim and duodenum (and pancreas) stimulated by amino acids Gastrin transporter via local blood supply to stimulate parietal cells and ECL cells to enhance acid secretion Gastrin also stimulated CCK receptors on D cells to release 5-HT which has a negative feedback effect on gastrin release (CCK - Chloecystokinin)
28
Why doesn't the stomach digest itself?
Mucousal barrier * tight junctions between mucosal and epithelial cells prevents leakage of gastric juice onto underlying tissue * mucous secreted by epithelial cells has higher pH, providing localised neutralisation and physical barrier to acid * prostaglandins increase mucosal thickness and stimulate bicarbonate production
29
Inhibition of gastric secretion
Occurs once food has left the stomach * neuronal inhibition - partially digested protein in duodenum inhibits secretion by "enterogastric reflex" - reflex mediated by medulla and leads to decreased Parasympathetic stimulation * hormonal inhibition - secretin and cholecystokinin released from duodenum - other inhibitors include motilin, GIP, gastrone, glucagon, VIP
30
Gastric motility
Results from contraction of the 3 layers of muscle in the stomach wall to: Grind, churn, knead, twist and propel contents Coordinated by myenteric plexus which receives input from ANS Parasympathetic stimulation increases motility Sympathetic stimulation decreases motility
31
Gastric emptying
Stimulated and inhibited in a similar manner to gastric secretion Emptying occurs at a rate proportional to gastric volume Physical and chemical nature of contents influences rate Stomach emptying involves: Constriction of lower oesophageal sphincter Contraction if gastric muscularis Relaxation of Pyloric sphincter
32
Absorption in the stomach
Stomach walls are impermeable to a range of compounds, though water, alcohol and some drugs and electrolytes can be absorbed Absorption usually only starts when contents reach small intestine where food is acted upon by products of pancreas, liver and gallbladder
33
Vomiting
Sudden and forceful oral expulsion of contents of stomach (and sometimes duodenum) Occurs due to reflex coordinated by reticular formation of medulla Activated by stretch, chemical agents, bacteria & toxins, sight, smell, motion, balance, pain, emotions, cytotoxic drugs etc Prolonged vomiting can cause metabolic alkalosis through loss of gastric acid
34
Vomiting and nausea is
* Triggered by afferent impulses to the emetic centre (from chemoreceptor trigger zone, vestibular system, limbic system or periphery) * Afferent impulses integrated by the emetic Centre * output to medullary control centres (vasomotor, respiratory) and subsequent somatic and visceral outputs to effector organs NAUSEA》FEELING OF MALAISE, UNEASE, DISCOMFORT IN STOMACH, URGE TO VOMIT
35
Structures of the small intestine- mucosa and submucosa
Mucosa Pits lined with glandular epithelium Intestinal glands secrete enzymes of digestive juices Submucosa Contains Brunner's glands which secrete alkaline mucous to - Protect intestinal wall Neutralise acid chyme
36
Structures of the small intestine- luminal surface
Covered in microvilli to increase absorptive surface area. Each villas has - * arterial * capillary bed * venule * lymphatic - for efficient transport of nutrients Folds of mucosa and submucosa further increase surface area
37
Intestinal juices
3-3L liquid with pH 7.6 produced per day Contains water, mucous and enzymes Secretion regulated by reflex stimulated by presence of chyme CCK and secretin also stimulate juice secretion
38
Digestion of the small intestine
Chemical - Digestive process started by salivary amylase and stomach pepsin Digestive process completed in small intestine by combined actions of - * pancreatic juice * bile * intestinal juice
39
Digestion of carbohydrate
* starch - converted to disaccharides by pancreatic amylase * disaccharides (sucrose and lactose) - converted to monksaccharide by glucoside * monosaccharide - absorbed (glucose, fructose, galactose
40
Digestion of proteins
* Polypeptides arriving from stomach catabolised by pancreatic trypsin and chymotrypsin * Digestion completed by peptidases released from glandular epithelium of the intestine * Peptidases cleave amino acids - carboxypeptidases act at "carboxyl" end - aminopeptidases act as "amino" end - dipeptidases convert dipeptides to amino acids
41
Digestion of fats
* Around 80g fat absorbed from intestine (jejunum) each day * Bile plays an essential part - fat globules in duodenum coated with bile salts to create emulsion and disperse fat molecules - facilitates breakdown of triglycerides by pancreatic lipases to form monoglycerides and free fatty acids
42
Digestion of nucleic acids
Ribonuclease and deoxyribonuclease break down respective nucleic acid nucleotides to constituent pentose and nitrogen base subunits Subunits are then absorbed through intestinal wall
43
Absorption in the small intestine
* Process by which digestion products transported into epithelial cells and blood * Almost all absorption occurs in small intestine * about 8-10L water and 1kg nutrients pass through gut walls daily * absorption through intestinal mucosa via - active transport - diffusion

Physiology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions