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Anatomy + Physiology (606) > Digestive System > Flashcards

Digestive System Flashcards

1
Q

lots of pictures

A

look at notes to practice with pictures

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2
Q

functions

A

ingestion
mechanical processing
digestion
secretion
absorption
excretion

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3
Q

gastrointestinal tract

A

oral cavity (teeth + tongue) > pharynx > oesophagus > stomach > small intestine > large intestine
accessory organs of digestive system - salivary glands, liver, gallbladder + pancreas

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4
Q

peritoneum + mesenteries

A

peritoneum:
serous membrane- visceral layer covers organs, parietal layer lines cavities
peritoneal fluid- 7l/ day, provides lubrication to allow sliding

mesenteries suspend portions of digestive tract
allow passage of blood vessels, nerves and lymphatic vessels

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5
Q

digestive tract

A

protects against:
digestive acids and enzymes
mechanical stresses
bacteria

histological organisation - four major layers
1. mucosa
2. submucosa
3. muscularis externa
4. serosa

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6
Q

digestive tract mucosa

A

superficial layer of digestive tract
mucosal epithelium has stratified squamous epithelium (oral cavity, pharynx, oesophagus) and simple columnar with mucous cells elsewhere
has lamina propia underneath with areolar tissue with blood and lymphatic vessels + nerve endings
underneath- muscularis muscosae- smooth muscle- inner circular layer, outer longitudinal layer
surface covered in villi + also folds, which increases SA

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7
Q

digestive tract submucosa

A

tougher, dense irregular connective tissue
allows passage of blood and lymphatic vessels
may contain exocrine glands- secretion of buffers + enzymes
submucosal plexus- neural network that innervates the mucosa and submucosa

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8
Q

digestive tract muscularis externa

A

smooth muscle cells- inner circular layer + outer longitudinal layer propel contents through digestive tract
movements coordinated by enteric nervous system- sensory neurons, interneurons, and motor neurones- innervated by para NS

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9
Q

digestive tract serosa

A

seroas membrance covering muscularis externa is most of digestive tract
replaced by adventitia (dense sheath of collagen fibers to attach adjacent structures) in oral cavity, pharynx, oesophagus + rectum

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10
Q

movement of digestive materials

A

rhythmic cycles of smooth muscle activity controlled by pacesetter cells (in muscularis mucis + muscularis externa)
cells undergo spontaneous depol - waves of contraction through entire muscular sheet
peristalisis- waves of muscular contraction
segmentation- cycles of contraction, does not follow a set pattern

  1. contraction of circular muscles behind bolus
  2. contrctio of longitudinal muscles ahead of bolus
  3. contraction in circular muscle layer forces bolus forward
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11
Q

oral cavity

A

functions- sensory analysis, mechanical processing, lubrication, limited digestion (carbs + lipids), passageway for liquids, food and air - opens to oropharynx

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12
Q

salivary glands

A

saliva- 1-1.5L a day produced
contains water (99%), electorlytes, buffers, mucins + antibodies
functions- lubricating mouth + contents, dissolving chemicals, initiating digestion of complex carbs by salivary amylase
salivary glands- parotid, sublingual and submandibular
produce saliva controlled by parasymp and symp stimulation

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13
Q

swallowing

A
  1. buccal phase
  2. pharyngeal phase
  3. oesophogal phase
  4. bosul enters stomach
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14
Q

oesophagus

A

conveys solid food and liquids to the stomach
resting muscle tone (contracting when not swallowing) in the superior 3cm of prevents air from from entering
adventitia anchors to surrounding structures
has stratified squamous epithelium, lamina propria and muscularis mucosae

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15
Q

stomach

A

major functions:
storage of ingested food, mechanical + chemical breakdown
chemical by enzymes- pepsin starts protein breakdown, continued activity of salivary amylase and lingual lipase , by acid (HCl) reduces pH to 2, helps to digest food and destroy pathogens
production of intrinsic factor- needed for b12 absorption

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16
Q

stomach lining

A

simple columnar epithelium- lines stomach and produces mucus
gastric pits connect gastric glands in mucosa onto gastric surface- cells at base divide, replacing superficial cells
smooth muscle (muscularis mucosa and muscularis externa)- oblique layer in additioon to circular and longitudinal layers

17
Q

stomach glands

A

gastric glands- in fundus and body of stomach
parietal cells- secrete intrinsic factor and HCl
chief cells- secrete pepsinogen (precursoR) convterted to pepsin by HCl
G cells- secrete gastrin which helps to increase activity in stomach
plyoric glands- in plyorus, produce mucous
G cells secrete gastrin + D cells release somatostatin (inhibits gastrin release)

18
Q

HCl secretion

A

by parietal cells
blood will be alkaline after eating due to large number of bicarbonate ions
1. carbonic anhydrase converts co2 and h2o to carbonic acid which dissociates to form H+ ions
2. contertransport mechanism ejects the bicarbonate ions and import chloride ions
3. chloride ions diffuse across the cell and exit through open chloride channels into the lumen of the gastric gland
4. hydrogen ions are actively transported into the lumen of the gastric gland

19
Q

stomach protection

A

mechanisms helping to protect the stomach from acid/ protease:
mucous lining, rapid cell division, seperate secretion of H+ and Cl- in parietal cells, secretion of inactive precursor eg pepsinogen, stimulation of secretion only when needed (sympathetic stimulation, local reflexes, gastrin) , inhibition of secretion - CCk, GIP, secretin

20
Q

regions of the small intestine

A

narrower than large intestine but very long
duodenum- 25cm long, netralises chyme, receives secretions from pancreas and liver, few plica circulares, small villi
receives secretions from stomach

jejunum- 2.5m long, location of most chemical digestion and nutrient absorption, prominent plica circulares and villi

ileum- 3.5m long, lymphoid nodules (peyers patches)

21
Q

intestinal wall

A

mucosa, muscularis mucosae, submucosa, muscularis externa, serosa
large villi, openings called intestinal crypts, lacteal

22
Q

functions in small inestine

A

intestinal glands- epithelial cells divide at base + are displaced towards tips of villi then disintegrate adding enzymes to lumen

brush border enzymes- integral membrane proteins on intestinal microvilli, break down materials in contact with brush border, enteropeptidase - activates pancreatic proenzyme trypsinogen

enteroendocrine cells- produce hormones in response to pH change/ nutrients, CCK and secretin (increase enzyme/ bile secretion), gastric inhibitory peptide- inhibits gastrin activity

duodenal glands- produces mucus + raises pH

intestinal juice- moistens chyme and keeps intestinal contents in solution + buffers acids

23
Q

pancreas

A

has ducts leading to small intestine
secretes pancreatic juice- contains pancreatic enzymes including pancreatic alpha amylase, pancreatic lipase, nucleases, proteases + peptidases (secreted as inactive proenzymes, activated after reaching small intestine)

24
Q

liver

A

located under diaphragm
2 veins- heaptic and vena cava
2/3 blood from hepatic portal vein- originates from oesophagus, stomach, small intestine, much of large intestine
1/3 blood from hepatic artery proper

25
Q

liver histology

A

100,000 hexagonal lobules
portal areas contain: branch of hepatic portal vein, branch of hepatic artery proper, branch of bile duct
blood flows past hepatocytes + absorbs soluts and secrete proteins sinusoids drain into to central vein + bile ductules into bile ducts

26
Q

liver functions

A

metabolic regulation:
metabolism of carb, lipid and aa, waste product removal (ammonia + toxins), vitamine storage (fat soluble, vitamins + B12), mineral storage, drug inactivation

haematological regulation:
phagocytosis and antigen presentation, synthesis of plasma proteins, removal of circulating hormones, antibodies + toxins

bile production:
bile salts break insoluble lipid droplets apart (emulsification), increases surface area exposed to enzymatic attack

27
Q

gall bladder + bile transport/ strorage

A
  1. liver secretes ~1L bile a day
  2. bile is stored and concentrated in gallbladder
  3. duodenal CCK release triggers dilation of the hepatopancreatic sphincter and contraction of gallbladder, bile is ejected into the duodenum
  4. bile salts break apart lipid droplets by emulsification
28
Q

large intestine- functions

A

absorption- reabsorption of water + bile salts, absorption of vitamins + organic wastes
site of bacterial vitamin production- vitamin K , biotin + vitamin b5
compaction of intestinal contents into faeces
storage of faeces until defacation

29
Q

large intestine- histology

A

lacks villi- smooth surface
abundant mucous cells
longitudinal layer of muscularis externa –> teaniae coli

30
Q

neural control of intestinal movement

A

central control- parasympathetic stimulation- increases motility and secretion , sympathetic stimulation inhibits

local relflex- to stretch/ pH change

central gastric reflexes- gastroentric reflex stimulates motility and secretion along the entire small intestine
gastroileal reflex triggers the opening of the ileocaecal calve allowing materials to pass from the samll intestine into the large intestine

31
Q

digestion

A

processing and absorption of nutrients:
macronutrients- complex carbs to polysac to monosac
lipids to fatty acids
proteins to polypeptides to aa
micronutrients- vitamins + minerals
water
molecules released into bloodstream are:
absorbed by cells, broken down to procide energy for ATP synthesis, used to synthesise carb, protein + lipids

Anatomy + Physiology (606) (15 decks)

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