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human anatomy and physiology > mouth to stomach > Flashcards

mouth to stomach Flashcards

1
Q

what parts of the body are involved in digestive processing

A

Mouth
Stomach
Small intestine
Large intestine
Pancreas (revisited!)
Liver
bile

the pancreas is revisited Because it is also part of the endocrine system.

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2
Q

why do we need the digestive system

A

Provides food source for all cells of body

Can be considered as a huge disassembly line

Delivers these nutrients through circulatory system

You literally are what you eat!

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3
Q

what is catabolism and what does it do to the components

A

Breakdown of large complex food into small simple components
- Amino acids & monosaccharides are universal building blocks

Absorb these small components

Distribute them to cells & tissues

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4
Q

what are the 4 functions of the digestive system

A

Ingestion (take food in)

Digestion (breakdown large molecules into small ones)

Absorption (nutrients –> cells of digestive tract —> blood)

Defecation (eliminate undigested residue)

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5
Q

name the organs involved in the digestive tracts

A

Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine

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6
Q

name the organs involved in the accessory organs of the digestive tract

A

Teeth
Tongue
Salivary glands
Liver
Gall bladder
Pancreas

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7
Q

what are the 3 steps to digestion

A
  1. Mechanical Processing - tearing & crushing with teeth - squashing & compaction by tongue
    - swirling, mixing & churning of stomach & intestines
  2. Chemical Breakdown - by digestive enzymes
  3. Secretion - release of water, acids, enzymes, buffers & salts by GI tract & glandular organs

GI = GastroIntestinal

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8
Q

dhow many layers are there in the GI tract

A

4

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9
Q

describe the layers of the GI tract

A

Same basic 4 layers in wall from lower oesophagus to anal canal

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10
Q

name the 4 layers of the digestive tracts and escribe

A

(lumen)

mucosa:
- epithelium (protective)
- lamina propria (small blood & lymph vessels, nerves)
- muscularis mucosa (sparse Smooth Muscle Cell layer)

SUBMUCOSA:
- (distensibility & elasticity; larger blood & lymph vessels; submucous plexus nerve network, termed “brain of gut”)

MUSCULARIS EXTERNA:
- (major SMC (smooth muscle cell) coat: circular to decrease diameter & longitudinal to propulse/mix; between is myenteric plexus nerve network)

SEROSA:
- (=serous membrane=lines body cavity, not open to external)

named MSMS for short

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11
Q

in different regions of the Gi tract there are what variations and describe

A

structural variations

Muscularis externa
- Stomach contains additional internal oblique muscle layer
- Upper oesophagus & sphincters of anus consist of skeletal muscle fibres

Serosa
- Continuous with mesentery, in most places
- Mesentery suspends digestive organs from inner wall of abdominal cavity

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12
Q

name the 3 main types of glands associated with the GI tract

A

Unicellular mucous glands in mucosa

Multicellular glands in mucosa & submucosa

Multicellular glands (accessory glands) outside GI

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13
Q

what is the mouth called

A

Oral or buccal cavity

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14
Q

name the functions of the mouth

A

Ingestion

Taste (& other sensory responses to food)

Mastication (chewing)

Chemical digestion (starch, in part)

Deglutition (swallowing)

Speech

Respiration

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15
Q

what is the mouth enclosed by

A

Cheeks
Lips
Palate
Tongue

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16
Q

the oral cavity is lines with what cells

A

stratifies squamous epithelium

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17
Q

what structure do the lips lead to

A

Oral orifice (lips)
lead to:
Fauces (throat)

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18
Q

what are the 2 different types of salivary glands

A

intrinsic
extrinsic

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19
Q

explain intrinsic salivary glands

A

Small, dispersed amid oral tissues:
Lingual (tongue)
Labial (inside lips)
Buccal (cheeks)

Small amounts saliva contain lingual lipase & lysozyme, moisten mouth & inhibit bacteria

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20
Q

explain extrinsic salivary glands

A

Larger, 3 pairs outside mucosa with ducts:
- Submandibular
- Parotid (swell with Mumps)
- Sublingual (floor)

which can produce:

Salivary or thinner
mucus fluid
(contains
amylas
& electrolytes)

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21
Q

what percentage of saliva is water

A

99.4%

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22
Q

what other than water is saliva made up of

A

0.6% includes assortment of :

  • Electrolytes (Na+, Cl-, HCO3-)
  • Buffers (pH ~7.0)
  • Glycoproteins = mucins (lubrication)
  • Antibodies (control bacteria)
  • Enzymes: lysozyme =
    antibacterial
    amylase = polysacc.
    —> disacc.
  • Waste products
23
Q

salivary secretion is constantly stimulated by what

A

by parasympathetic nerve endings

24
Q

how do parasympathetic nerve endings control salivary secretion

A

Trigger reflex

  • Object in mouth
  • Empty chew/smell/think
    e.g., just thinking about pickled onions
25
Q

describe the stomachs shape

A

Muscular J-shaped sac

26
Q

what does the stomach do

A

Food storage organ

Mechanically breaks up food particles

Liquefies food

Begins chemical digestion of proteins & small amounts fat,
into, chyme (soupy mixture)

  • (most digestion occurs once passed into small intestine)
27
Q

name the regions the stomach is divided into

A

Cardiac (near heart)
Fundus
Body (main region)
Pyloric (near sphincter)

28
Q

what happens to the stomach structure if its empty

A

mucosa forms folds = rugae

29
Q

explain the cells lining the stomach

A

All portions of stomach lined by simple columnar epithelium, producing a carpet of protective mucus

30
Q

describe the mucosa’s structure/cells

A

Mucosa full of shallow depressions = gastric pits

  • Cells at base dividing to continuously replace old cells (3-7 days) by migrating up towards lumen (or down)
31
Q

explain stomach glands in terms of location

A

At base of each gastric pit opens 2 or 3 tubular glands

32
Q

how are stomach glands named and name some

A

named according to location in stomach:

  • Cardiac glands
  • Pyloric glands
  • Gastric glands (in fundus & body)
33
Q

how do glands in the stomach differ

A

differs in cellular composition & therefore what they secrete
In general:

Cardiac glands produce mucus Throughout which produces hormones.
Gastric glands produce acid and enzymes, which are gastric juice (2-3L/day including water)

34
Q

explain gastric secretions of hydrochloric acid

A

Hydrochloric acid secreted by gastric parietal cells

HCl is not produced inside parietal cell
- would destroy it (pH can be as low as 0.8!)

Instead, H+ & Cl- transported independently by different mechanisms

35
Q

explain the process of HCl secretion by parietal cells

A

Parietal cell takes CO2 from blood & combines it with water to make carbonic acid (H2CO3)

Carbonic acid breaks down into bicarbonate ion (HCO3-) & H+

H+ pumped into lumen of stomach in exchange for K+ by an H+-K+ ATPase

Bicarbonate ion returned to blood in exchange for Cl-

Cl- follows H+ into lumen, where they constitute HCl

36
Q

what are the functions of stomach acid

A

Activates pepsin & lipase

Breaks up connective tissues & plant cell walls (liquefy & form chyme)

Converts ferric (Fe3+) ferrous (Fe2+) so can be absorbed & form Haemoglobin (Hb)

Destroys ingested bacteria etc.,

37
Q

explain the intrinsic factor

A

Parietal cell glycoprotein essential for absorption of vitamin B12 by small intestine

Without it, cannot synthesize Haemoglobin

Leads to pernicious anaemia (fatal)

If gastrectomy this leads to requirement for regular Vit B12 (remove stomach) injection

  • Vit B12 intramuscular injections only required every 3 months, as liver has large storage capacity for Vit B12 (cf. oral intrinsic factor (IF) or oral Vit B12; latter absorbed slowly in absence of IF). Anaemia not develop for several years due to liver storage.
38
Q

what do chief cells do in terms of with producing pepsin

A

secrete the inactive enzyme (thus a zymogen) pepsinogen

39
Q

what does HCL (from the parietal cells do to pepsinogen from chief cells

A

converts this inactive enzyme to the active enzyme pepsin

40
Q

what does pepsin digest

A

protein

41
Q

Once Pepsin is formed (from chief cells and HCL), it can activate what

A

activate its precursor, pepsinogen

  • Pepsin can act as an autocatalyst, causing production of more of itself.
42
Q

what other enzymes do chief cells secrete

A

In infants, chief cells also secrete:
- Gastric lipase –> digests butterfat of milk
-Rennin –> curdles milk by coagulating proteins

(Note: not the enzyme renin secreted by kidneys, which forms angiotensin to increase BP)

43
Q

how many chemical messengers are there in digestion

A

20

44
Q

what cells secrete hormones that are chemical messengers

A

Enteroendocrine cells

45
Q

name and describe the chemical messenger hormones that Enteroendocrine cells secrete

A

Gastrin:
- stimulates gastrin gland ( HCl & enzymes) & intestinal motility
- relaxes ileocecal valve

Serotonin:
– stimulates gastric motility

Histamine:
– stimulates HCl secretion

Somatostatin:
- inhibits gastric secretion & motility, pancreas secretions, gallbladder contraction & bile secretion
- delays emptying of stomach
- reduces blood circulation & nutrient absorption in small intestine

46
Q

what is gastritis

A

inflammation of gastric mucosa (due to alcohol, aspirin, stress, bacterial infection, strong acids/alkalines)

47
Q

what is a peptic ulcer and hows it treated

A

erosion through lining
- Gastric
- Duodenal

Treat with antibiotics
or cimetidine
- H2 histamine receptor antagonist
to reduce acid production

48
Q

what is peristalsis

A

Waves of muscular relaxations followed by waves of strong contractions that moves material through most of GI

49
Q

why do we need Regulation of Gastric Function

A

To cope with full & empty stomach

50
Q

regulation of gastric function is divided into how many stages and what does this depend on

A

Divided into 3 stages, depending on whether control from:
brain,
itself or
small intestine

51
Q

name the 3 stages of regulation of gastric function

A

cephalic
gastric
intestinal

52
Q

explain the cephalic stage of regulation of gastric function

A

function:
prepare stomach for food arrival

duration:
short (mins)

mechanisms:
Neural (CNS) eg. think/chew food

action:
increase vol of gastric juice

53
Q

explain the gastric stage of regulation of gastric function

A

function:
enhance secretions; homogenise & acidify chyme; pepsin

duration:
long (3-4hrs)

mechanisms:
Neural (stomach distention) Hormonal Local

action:
increase acid, pepsinogen

54
Q

explain the intestinal stage of regulation of gastric function

A

function:
Control rate of chyme entry to duodenum

duration:
long (hours)

mechanism:
Neural (contents enter duodenum), Hormonal secondary

action:
inhibit gastric motility phase

human anatomy and physiology (52 decks)

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