Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HLTH1030 > the gastrointestinal tract > Flashcards

the gastrointestinal tract Flashcards

1
Q

describe the evolution of the digestive system

A
  • intracellular digestion in vacuoles: simplest of all digestive compartments, intracellular organelles filled with digestive enzymes, protozoa and sponges
  • gastrovascular cavities: single opening, extracellular digestion and distribution of nutrients, digestive compartment surrounded by cells, specialisation of cells
  • digestive tubes: two openings (mouth and anus), alimentary canal (specialised)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

describe the two classifications of the digestive system

A
  • alimentary canal (GI): continuous muscular tube, mouth to anus, digests and absorbs food
  • accessory digestive organs: teeth, tongue, salivary glands, gallbladder, digestive glands, liver, pancreas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

describe basic anatomy of the alimentary canal

A
  • F: compartmentalisation, regionalisation and specialisation, sequential digestion controlled by sphincters, accessory organs and glands
  • O: mouth (entrance), salivary glands (digestion of starch), oesophagus (food to stomach), stomach (protein digestion), liver, pancreas, small intestine (digestion and absorption), large intestine (reabsorption) and anus (excretion)
  • S: mucosa (epithelium, lamina propria and muscularis mucosae), submucosa, muscularis externa (circular and longitudinal layer) and serosa (connective tissue and mesothelium)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the essential activities of the alimentary canal

A
  • ingestion
  • propulsion
  • digestion
  • absorption
  • compaction
  • defecation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is ingestion

A
  • simply taking food into the digestive tract, usually via the mouth
  • involves mouth (oral / buccal cavity)
  • mouth: bounded by lips anteriorly, cheeks laterally, palette superiorly and tongue inferiorly, oral orifice (anterior opening)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

describe the function and anatomy of the mouth

A
  • function: ingestion, chewing, speech, respiration, digestion and swallowing
  • chewing: mechanical breakdown of food, buccinator muscles (chewing, whistling, smiling, suckling), masseter muscle (mandible upwards), temporalis and medial / lateral pterygoid
  • lined with stratified squamous epithelium
  • keratinised: food abrasion (gum / hard palate)
  • non keratinised (floor, soft palate, cheeks and lips)
  • lips: labia, suckling
  • cheeks: composed of buccinator muscles, stratified squamous epithelium
  • dental formulas: count one side of maxilla and one side of mandible (x2) = total teeth (humans = 2,1,2,3)
  • incisors: anterior, scraping or biting, scoop shaped, smaller
  • canines: ripping or tearing, long and pointed
  • premolars:posterior to canines, flat for grinding, or sharp / serrated for tearing
  • molars: vary, depending on use, often grinding, but may beserrated/ sharp edges for ripping and tearing meat
  • tongue: gripping, repositioning, mixing of food during chewing, interlacing bundles of skeletal muscle, covered in papillae (taste receptors, rough surface)
  • papillae (foliate, filiform, fungiform and circumvallate), filiform papillae have keratinised tips, foliate are elongated and leaf shaped
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is saliva / salivary glands

A
  • saliva: 97-99.5% water, mucin (protein), salivary amylase, lingual lipase, antibodies (lgA), helps in first break down of food (enzymes present)
  • salivary gland: serous cells (produce watery secretion, enzymes, ions and mucin) and mucous cells (produce mucous)
  • extrinsic: parotid and submandibular (serous), sublingual (mucous)
  • function: connect to oral cavity by ducts, secrete up to 1.5L of saliva per day
  • intrinsic: lingual, labial, buccal
  • function: produce lingual lipase and lysozyme, secrete saliva at a fairly constant rate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is propulsion

A
  • involves swallowing (oropharynx) and peristalsis (oesophagus, stomach, small / large intestine)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

describe anatomy of the oesophagus

A
  • S: flat muscular tube that runs from the laryngopharynx to the stomach, collapsed when not involved in food propulsion, four alimentary canal layers
  • mucosa: stratified squamous epithelium (protects)
  • submucosa: oesophageal glands (secrete mucous), veins, arteries, lymph, loose areolar connective
  • muscularis externa: longitudinal / circular muscle
  • adventitia: instead of serosa, fibrous connective tissue
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is peristalsis vs segmentation

A
  • P: coordinated / rhythmic contractions of the longitudinal muscles and circular muscle, adjacent segments alternately contract and relax
  • S: nonadjacent contraction / relaxation of the circular muscles in the digestive tract, additionally mixes food
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a sphincter and the different types

A
  • control passage of material
  • upper oesophageal (pharynx and oesophagus)
  • lower oesophageal / cardiac (oesophagus and stomach)
  • pyloric (stomach and small intestine / duodenum)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is a bolus vs chyme

A
  • B: what you swallow, chewed food mixed with saliva
  • C: what goes into the small intestine (duodenum) from the stomach, partially digested food and digestive juices (acids and enzymes)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the function and structure of the stomach

A
  • temporary storage, digestion (chemical breakdown of proteins), absorption
  • converts bolus of food into chyme and is the gatekeeper to the small intestine
  • rugae: many folds of mucosa that form when the stomach is empty (~50mL)
  • digestion: mechanical (churning) and chemical (pepsin partially digests protein into shorter peptide chains), gastric lipase and lingual lipase begin fat digestion
  • absorption: of water, alcohol and some medication (aspirin and anti-inflammatories)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe macroscopic histology of the stomach

A

mucosa:
- three layers, tight simple columnar epithelium
- surface mucous cells: simple columnar epithelia, gastric pit (secrete alkaline mucous) lead to gastric glands (secrete gastric juice)
- lamina propria: areolar connective tissue, reabsorb nutrients, supports epithelium
- muscularis mucosa: smooth muscle

submucosa: contains submucosal plexus (gut brain), veins, arteries, lymphatic vessels
muscularis: oblique layer (inner), circular layer (middle) and longitudinal layer (outer)
serosa: lining of the stomach / stomach wall

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

describe the features of gastric protection

A
  • mucous layer, bicarbonate secretion, epithelial tight junctions, mucosal blood flow and prostaglandins
  • mucosal barrier: protects stomach, thick bicarbonate mucous, tight junctions between epithelial cells prevent juice seeping underneath tissue
  • mucosal blood flow: supplies mucosa with O2 / bicarbonate and removes H ions and toxic agents, supports healing of superficial lesions developing into deeper lesions
  • prostaglandins: inhibit acid secretion and stimulate mucous and bicarbonate secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

describe the microscopic anatomy of the stomach

A

stem cells: rapid division and supply of new cells

gland cells: in funds and body produce most gastric juice, secretory cells

mucous neck cells: secrete thin acidic mucous

parietal cells: secrete HCl and intrinsic factor

  • HCl: pH 1.5-3.5, denatures proteins, activates pepsin, breaks down cell walls and kills bacteria
  • intrinsic factor: glycoprotein required for absorption of vitamin B12 in small intestine

chief cells: secrete pepsinogen and lipase

  • pepsinogen: inactive enzyme, activated by HCl or pepsin to become pepsin
  • pepsin: digestive enzyme which breaks down proteins into peptides
  • lipase: breaking down and digestion of ~15% of lipids

enteroendocrine cells: secrete chemical messengers into lamina propria

  • paracrines: serotonin / histamine
  • hormones: somatostatin (endocrine / paracrine, d-cells, acid inhibition) and gastrin (endocrine, g-cells, acid secretion), low pH inhibits gastrin secretion (between meals / during digestion)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is acid and how is acid secretion controlled

A
  • kills bacteria, aids in digestion and provides an optimal pH for pepsin (1.5-3.5)
    1. g cells in pyloric antrum of stomach release gastrin (peptide hormone)
    2. gastrin stimulates activation of enteroendocrine cells (ECL) to release histamine
    3. histamine stimulates secretion of gastric acid (HCl) by the parietal cells
    4. neurons release acetylcholine due to increased release of gastrin, histamine and HCl
    5. increased HCl causes secretion of somatostatin by somatostatin releasing cells
    6. somatostatin inhibits secretion of gastrin, histamine and HCl
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

describe the structure and function of the pharynx

A
  • food passes from mouth to oropharynx then into laryngopharynx (larynx), allows passage of foods fluids and air
  • S: stratified squamous epithelium lining with mucous producing glands), external muscle layers consist of two skeletal muscle layers for swallowing
  • swallowing:
    1. bolus is pushed to the back of the tongue
    2. tongue pushes against palate and food is propelled to the pharynx
    3. soft palate blocks nasal cavity
    4. swallowing reflex takes over and epiglottis closes over the larynx and trachea
    5. food propelled down the oesophagus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how does regulation of gastric emptying occur

A
  • duodenum can control how much chyme enters intestine
  • duodenal receptors respond to stretch and chemical signals
  • enterogastric reflex and enterogastrones inhibit gastric secretion / duodenal filling, stomach empties ~4 hours
  • increase in fatty chyme entering the duodenum can increase time to 6 hours or more (carbohydrate chyme moves quickly through)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

describe the structure of the liver

A
  • largest gland, thin capsule of dense connective tissue. 1.2-1.6 kg, four primary lobes (right, left, caudate, quadrate)
  • falciform ligament: separates larger right and smaller left lobes, suspends liver from diaphragm and attaches liver to the ventral body wall
  • round ligament: remnant of foetal umbilical vein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

describe the function of the liver

A
  • high metabolic activity, detoxification (via filtering), more than 500
  • purification transformation clearance: toxins, drugs, hormones, ammonia to urea, bilirubin
  • storage: glycogen, vitamin A, vitamin B12, iron and copper
  • immunity: secretory IgA
  • metabolism: carbohydrates, amino acids and fats
  • energy homeostasis: glycogenesis, glycogenolysis, gluconeogenesis, ketogenesis, repackaging excess fatty acids
  • synthesis / secretion: albumin, plasma proteins, clotting factors, transport proteins (apolipoproteins, transferrin, hormone binding proteins), insulin like growth factor 1 (IGF1), cholesterol, bile salts and glutathione
  • filter: remove potentially harmful xenobiotics (chemical compounds that are foreign)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is hepatic circulation

A
  • dual blood supply: liver is one of the organs that has dual blood supply
  • liver receives: arterial blood from hepatic artery (from heart) and from the hepatic portal vein (from small intestines),
  • liver sinusoids: branches of hepatic portal vein and hepatic artery empty together and mix
  • leaves liver: through hepatic vein which becomes the inferior vena cava
  • hepatic arterial: liver receives ~30% arterial blood from hepatic artery highly oxygenated
  • hepatic portal: liver receives ~70% venous blood from organs of the GI tract (and spleen) through hepatic portal vein, contains nutrients absorbed from GI tract, oxygen poor
23
Q

describe microscopic anatomy of the liver

A
  • liver lobules: hexagonal structural and functional units
  • portal triad: each corner of a lobule contains branch of hepatic artery (supplies oxygen from heart), hepatic portal vein (brings nutrient rich blood from intestine), a bile duct (receives bile from bile canaliculi), lymphatic vessels and branch of vagus nerve
  • hepatocytes: liver cells, 80% of cells in liver, filter and process nutrient rich blood, increased R and S ER, golgi body, peroxisomes and mitochondria
  • H function: produce bile, process blood nutrients, store fat-soluble vitamins and perform detoxification
  • central vein: located in longitudinal axis
  • liver sinusoids: BV, leaky capillaries between hepatic plates
  • stellate / hepatic macrophages: kupffer cells, line walls of sinusoids, star-shaped, phagocytic, remove debris and old RBC, bacteria, viruses, cell debris
24
Q

what is bile

A
  • dark green / yellow fluid, produced by liver hepatocytes, collected in lobule canaliculi
  • S: water (97%), bile salts for fat emulsification / absorption (0.7%), bilirubin (0.2%), fats / cholesterol (0.5%) and electrolytes (the rest)
  • enterohepatic circulation: 95% of secreted bile salts are recycled, reabsorbed into blood by ileum, returned to liver via hepatic portal blood (only 5% newly synthesised), re-secreted in new bile
  • F: bile salts emulsify fats in intestine, surround fat droplets to form micelles (increase SA for lipase to break down)
  • fat is water repellent but enzyme responsible for fat digestion (lipase) is water soluble
25
Q

what is the gall bladder

A
  • S: thin walled muscular sac, simple columnar epithelium, honeycomb folds allow it to expand as it fills
  • L: attached to visceral layer of liver on ventral liver
  • F: receives and stores bile from liver via hepatic and cystic duct, muscular contractions release bile via cystic duct which flows in the bile duct
  • store and concentrate bile by absorbing water and ions, bile reservoir
  • gallstones: binary calculi, too much cholesterol / too few bile salts
26
Q

describe structure and function of the pancreas

A
  • S: no distinct capsule, covered by a thin layer of loose connective tissue
  • L: mostly retroperitoneal, deep to greater curvature of the stomach, head is encircled by duodenum and tail touches the spleen
  • F: both exocrine (produces pancreatic juice) and endocrine (secretion of insulin / glucagon)
27
Q

describe the endocrine pancreas

A
  • secretion of insulin and glucagon by pancreatic islet cells (islets of langerhans), clumps of secretory cells supported by reticulin fibres containing fenestrated capillaries
  • S: delicate capsule around each islet, paler than surrounding exocrine cells due to less rough ER, islets do not have an acinar organisation
  • islets of langerhans: 20% alpha (secrete glucagon), 75% beta (secrete insulin, synthesis of glycogen, protein and fatty acids, facilitates uptake of glucose, activates glucokinase), 5% delta (secrete somatostatin, paracrine, inhibits other endocrine cells)
28
Q

describe the exocrine pancreas

A
  • packed serous acini (clusters of secretory cells, acinar cells), produce zymogen granules containing proenzymes, secrete enzyme rich alkaline fluid into duodenum via pancreatic duct
  • alkaline pH: due to HCO3, neutralise acidic chyme
  • enzymes: digest proteins, carbohydrates, lipids and nucleic acids
  • ducts: secrete to duodenum via main pancreatic duct, smaller duct cells produce water / bicarbonate
  • secretes: acini empties into ducts lined with simple low cuboidal epithelium, which becomes stratified cuboidal in larger ducts
  • proteases (protein, inactive, prevents self digestion), lipase (fat), amylase (carbohydrates) and bicarbonate (neutralise)
29
Q

describe the pancreas and pancreatic juice / hormones

A

pancreatic juice:

  • 1200-1500 ml daily, contains watery alkaline solution (pH 8), electrolytes, primarily bicarbonate and digestive enzymes, suppress gastric acid secretion
  • F: neutralises gastric acid and acidic chyme in duodenum, enzymes break down protein (protease), fat (lipase) starch (amylase) and nucleic acids (nucleases)
  • composition: acinar cells secrete digestive enzymes (proteases, lipase’s, amylase and nucleases) and duct cells secrete bicarbonate and alkaline water solution

hormones:
- glucagon (alpha cells, stimulates breakdown of glycogen in liver and gluconeogenesis), insulin (beta cells, glucose uptake by muscle / fat
- stimulate storage of glucose in liver), somatostatin (delta cells, suppressed stomach acid production)

30
Q

list the activation of pancreatic proteases in the SI

A
  • trypsinogen (inactive) from pancreas + membrane bound enteropeptidase or trypsin = trypsin
  • chrymotryopsinogen (inactive) from pancreas + trypsin = chymotrypsin
  • procarboxypeptidase (inactive) from pancreas + trypsin = carboxypeptidase
31
Q

describe the structure and secretions of the SI

A
  • hepatopancreatic ampulla: bulblike structure, bile and pancreatic duct unite in wall of duodenum
  • major duodenal papilla: volcano shaped opening of ampulla into duodenum
  • hepatopancreatic sphincter: controls entry of bile and pancreatic juice into duodenum
  • control of secretions: bile and pancreatic juice secretions both stimulated by neural / hormonal controls
  • cholecystokinin: detects protein and fat in duodenum, secrete digestive enzymes
  • secretin: detects acid in duodenum, secrete bicarbonate and water
  • gastrin: detects stomach distention, secretes digestives enzymes
  • mucosa: simple columnar brush border of vili
  • submucosa: veins, arteries, lymph, payers patch (kill bacteria), Bruner’s gland (neutralise)
  • muscularis: longitudinal / circular muscle, myenteric plexus (gut brain)
  • serosa: intestinal wall
32
Q

describe the function of the SI

A
  • digestion: catabolic, breaks macromolecules into monomers by enzymes
  • absorption: moving substances from lumen of gut through apical membrane of epithelial cells into body via basolateral membrane
  • most nutrients are absorbed before chyme reaches ileum
    occurs via diffusion, facilitated transport, osmosis and active transport
  • subdivisions: duodenum (0.25m), jejunum (2.5m) and ileum (3.6m)
33
Q

describe an overview of lymph vessels

A
  • return fluids leaked from BV to blood, lymph entering lymphatics between capillaries (interstitial fluid and bigger fragments not fitting into capillaries)
  • lymph: salt, water, AA, protein, hormones, waste products
  • lacteals: specialised lymph capillaries present in intestinal mucosa (absorb digested fat)
  • pathway: capillaries drain into larger lymph vessels, similar to veins (valves), but are more permeable and can take up larger molecules
34
Q

describe the 4 modifications of the SI to increase SA

A

plicae circulares:
- permanent circular folds ofmucosa & submucosa
- form transverse to spiral ridges, ~1 cm deep, force chyme to spiral through lumen, increase SA ~ 3 fold
- increased contact with mucosa, more time for nutrient absorption promote thorough mixing
- absent from first cm’s of duodenum - middle of ileum
contain villi and crypts of lieberkuhn

villi:

  • projections of mucosa, ~1 mm, folds of epithelium, tall columnar absorptive cells (enterocytes and mucous secreting goblet cells), increase SA ~10 fold
  • dense capillary bed: transports sugars and AA away to maintain conc. gradient, capillaries unite to form larger blood vessels (hepatic portal vein - liver)
  • dense lymphatic bed: lacteal, absorption of dietary fats, associated with gut immune response

crypts of lieberkuhn:

  • invaginations of epithelium between villi, various cells
  • extend through lamina propria down to muscular mucosa, secretion of intestinal juice

microvilli:
- projections of columnar epithelial cells lining SI, on apical surface of enterocytes, velvet
- ‘brush border’: fuzzy appearance (membrane bound enzymes for final carbohydrate / protein digestion), increase of absorptive SA ~20 fold
- S: ~1 um L, ~90 nm D, bundles of parallel actin held together by cross linking proteins, around 3000 per cell (single enterocyte cell)

35
Q

describe the different types of epithelial cells in the SI

A

enterocytes:
- absorb nutrients, make up the bulk of all epithelial cells, simple columnar cells lining villi & crypt, contain many microvilli on apical surface, bound by tight junctions
- F: absorption of nutrients and electrolytes, in crypts production of intestinal juice

goblet cells:

  • secrete mucin which absorbs water and becomes mucous
  • mucous lubricates and protects epithelium from lumenal contents

enteroendocrine cells:

  • group of different cells, secreting various gastrointestinal hormones (secretin, pancreozymin, enteroglucagon etc)
  • scattered in villi and in some crypts
  • enterogastrones: secreted by duodenal mucosa when fatty food is present (cholecystokinin / CCK)

paneth cells:

  • exocrine cells, secrete antimicrobial peptides (defensins and lysozyme)
  • found deep in crypts, can destroy bacteria as part of the body’s innate immune protection from pathogens

stem cell:

  • deep in crypts (1-4 per crypt), self renew, continuously divide to produce other cells (progenitor cells), can produce all other epithelial cell types
  • new cells: migrate up side of villi, epithelium renewed around every 3rd day
  • chemotherapy: targets rapidly dividing cells, also targets rapidly dividing GI tract epithelium, symptoms of nausea, vomiting and diarrhoea
36
Q

what is the duodenum

A
  • receives chyme from stomach, bile and pancreatic enzymes from hepatopancreatic ampulla
  • stomach acid is neutralised, pepsin is inactivated by high pH, fats are emulsified by bile salts, chemical digestion by pancreatic enzymes
  • relate to exocrine pancreas, pancreatic juice composition, function of bile in digestion
  • brunner’s glands: only in duodenum, ducts of individual glands unite with overlying intestinal glands (crypts), produce mucous and bicarbonate), protect underlying mucosa from gastric acid and pancreatic enzymes by neutralising stomach acid in duodenum (high pH)
37
Q

what are nutrients and what is GI

A
  • nutrients: substance in food the body uses to promote normal growth, maintenance and repair
  • glycemic index: carbohydrate content in foods according to how they affect BG levels
  • low GI: <55, slowly digested, absorbed and metabolised, cause a lower and slower rise in BG and, therefore insulin levels
  • high GI: >60, quickly digested, cause a rapid increase in BG, followed by rapid decrease
38
Q

what are the main digestive processes in the body

A
  • enzymes: work most efficiently at optimal temperature and optimal pH
  • main processes: carbohydrate digestion, protein digestion, nucleic digestion and fat digestion
39
Q

describe carbohydrates / starch

A
  • benefits: except for lactose and a negligible amount of glycogen in meat, all carbohydrates we ingest are derived from plants
  • sugars: mono / disaccharides, sugar cane, fruit and honey
  • starch: polysaccharides, grains and vegetables
  • fibre: polysaccharides, cellulose is not digested provides roughage, insoluble fibre increases bulk of stool and soluble fibre is found in pectin in apples and citrus reduces blood cholesterol
40
Q

describe the process of digestion / absorption of starch

A

D:
- mouth + salivary amylase and duodenum + pancreatic amylase to disaccharides
- brush border enzymes in SI (maltase, lactase, sucrase) digest di into monosaccharides (glucose, galactose, fructose)
A:
- only monosaccharides
- they then leave epithelial cells via facilitated diffusion, enter capillary blood in villi and transported to liver via HPV
- glucose / galactose absorbed at apical surface of epithelial via co-transport with Na+
- fructose passes apical surface of absorptive epithelial via facilitated diffusion

41
Q

describe proteins

A
  • source: animal products contain the best ratio of essential amino acids (eggs, milk, fish, most meats), plant based are best for essential amino acids (soy beans, legumes, nuts)
  • ingested food, secretions (mucous / enzymes), enterocytes which have sloughed off
42
Q

describe the process of digestion / absorption of proteins

A

D:
- stomach (pepsinogen to pepsin at low pH, inactive at high pH of duodenum) produce large polypeptides
- pancreatic enzymes (trypsin, chymotrypsin, carboxypeptidase) break down to small polypeptides & small peptides
- brush border enzymes break down into amino acids
- some peptidases stored as inactive zymogens to protect cells which produce them
A:
- amino acids, di / tripeptides
- AA co-transported across apical of absorptive epithelial cell via secondary active transport with Na+
- some di / tripeptides via co-transport with H+ and hydrolysed to AA within cells
- AA leave epithelial cells across basolateral by facilitated diffusion, enter capillary blood in villi, and are transported to liver via HPV

43
Q

describe nucleic acids and their digestion / absorption

A
  • nuclei: of ingested cells in food contain DNA and RNA
    D / A:
  • pancreatic nucleases hydrolyse nucleic acid to nucleotide monomers
  • brush border enzymes, nucleosidases, and phosphatase’s break nucleotides into free N bases, pentose sugars, and P ions
  • products actively transported by carriers in epithelium of villi, then absorbed into capillary blood in villi
44
Q

describe fats

A
  • benefits: thermal insulator, produce hormones (oestrogen, leptin), has receptors for insulin, GH and adrenaline, protect / support organs / bones
  • most lipids are ingested as triglycerides
  • concentrated source of energy (9kcal/g), some nutrients need fat for the body to use them
  • lipid: fat, insoluble in water, soluble in an organic solvent, provide energy
  • saturated fats (butter, cream, meat fat)
  • trans-fats (created by hydrogenation, behave like saturated fats, margarine, chips, energy bars)
  • monounsaturated (vegetable oil, avocado)
  • polyunsaturated fats (tuna, salmon, nuts, soy products)
  • essential fatty acids (cannot be synthesised by the body, omega-3 and -6)
  • nonessential fatty acids (saturated, trans, omega-9)
45
Q

describe the process of digestion / absorption of fats

A

D:
- bile salts emulsify lipids insoluble in water and break large fat globules into smaller ones
- pancreatic lipase’s break down triglycerides into monoglyceride + 2 fatty acids
- micelle formation: fatty acids and monoglyceride’s become coated with bile salts / lecithin
A:
- lipid products leave micelles and cross epithelial membrane via simple diffusion
- chylomicron formation: monoglyceride’s and free fatty acids are converted back into triglycerides and packaged with lecithin and lipoproteins
- chylomicron are exocytosed from basolateral side, enter lymphatic lacteal of villi via pores
- chylomicrons are broken into free fatty acids and glycerol by lipoprotein lipase
- some short-chain fatty acids are absorbed, move into capillary blood in villi by diffusion, and are transported to the liver via the HPV

46
Q

describe the process of digestion / absorption of vitamins, electrolytes and water

A
  • V: vit. B12 binds with intrinsic factor (produced by parietal cells in stomach), absorbed by endocytosis in ileum, some hydrophobic vitamins (A, D, E and K) absorbed with lipids
    water-soluble vitamins (C and B) are absorbed by diffusion or by passive or active transporters
  • E: transported actively along SI (Na+, Cl-), K+ diffuses in response to osmotic gradient and Ca2+ absorption is regulated by vit D and PTH
  • W: 95% is absorbed in the SI by osmosis, rest is absorbed in LI, water uptake is coupled with solute uptake
47
Q

describe the large intestine structure, function and histology

A
  • S: 1.5m, cecum and appendix, colon (ascending, transverse, descending and sigmoid), rectum and anal canal
  • F: absorption of water (remaining 5%) and electrolytes (NaCl), digestion of some remaining food residues by enteric bacteria, formation / compaction of faeces, haustral churning and propulsion / storage of faeces
    and defecation (triggered by rectal distension)
  • H: thick mucosa of simple columnar epithelium (absorptive cells), mucosa is smooth, deep crypts with many mucous-producing goblet cells
48
Q

describe gross anatomy of the LI

A
  • teniae coli: three bands of longitudinal smooth muscle in muscularis
  • haustra coli: sac / pocket sacs caused by tone of teniae coli, inside semilunar folds cause by contraction of teniae coli
  • epiploic appendices: mental appendices, fat-filled pouches / projections of visceral peritoneum / serosa attached to the outside wall
  • cecum: T- shaped dead-end pouch between SI and LI
  • rectum: 3 rectal valves stop faeces from being passed, simple columnar epithelium
  • anal canal: last segment of LI, opens to anus, non-keratinised stratified squamous epithelium
  • internal anal sphincter: smooth muscle of muscularis externa, involuntary control
  • external anal sphincter: skeletal muscle of pelvic diaphragm, voluntary control
  • mucosa: simple columnar, crypts, goblet cells
  • submucosa: veins, arteries, lymph
  • muscularis: muscle (peristalsis)
  • serosa: colon wall
49
Q

what is bacterial flora

A
  • bacteria: consists of >1000 different types of bacteria, bacteria outnumber our own cells 10 to 1
  • metabolic functions: fermentation (ferment indigestible carbohydrates and mucin, release irritating acids and gases) and vitamin synthesis
  • beneficial bacteria: outnumber / suppress pathogenic bacteria, immune system destroys bacteria that try to breach mucosal barrier
50
Q

describe inflammatory diseases of the bowel

A
  • crohn’s disease: inflammation of the entire wall of the bowel, caused by combination of genetic and environmental factors
  • ulcerative colitis: inflammation of the superficial layers of the bowel wall (innermost layer)
51
Q

what is the appendix

A
  • worm-like extension from the caecum, in humans ~9cm, some immune function
  • appendicitis: acute inflammation of appendix, usually due to blockage by faeces that traps infectious bacteria which often results in appendectomy
52
Q

explain the table of main digestive processes

A 
carbohydrates:
- salivary amylase, salivary glands, mouth, neutral
- pancreatic amylase, pancreas, SI, basic
- maltase, SI, SI, basic
proteins:
- pepsin, gastric glands, stomach, acidic
- trypsin, pancreas, SI, basic
- peptidases, SI, SI, basic
nucleic acids:
- nuclease, pancreas, SI, basic
- nucleosidases, pancreas, SI, basic
lipids:
- lipase, pancreas, SI, basic
53
Q

provide a summary of hormones released in the GI

A
  • cephalic phase: brain, vagus, stimulate g cells (gastrin, muscle contractions) , enterocrhomafin like and parietal (histamine, activate parietal), parietal (HCl, pH, activates pepsinogen to pepsin etc), chief (pepsinogen / gastric lipase)
  • gastric phase: stretching (parietal activation), protein (stimulate g cells), ileocaecal valve relaxes (stretching)
  • intestinal phase: stretch causes CCK and secretin (gall bladder contraction, release bile), stimulate d cells (release somatostatin, slow down)

HLTH1030 (9 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions