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Flashcards in Digestive system Deck (68)
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1

Enamel

- crystalline rods or prisms of calcium, phosphate and carbonate
- NO CELLS
- HARDEST tissue of the body
- no sensation

2

Dentin

similar to bone, except cells (ODONTOBLASTS) occur in the nearby pulp, rather than scattered throughout

3

pulp of the tooth

- soft tissue
- blood vessels
- nerves
- lymphatics

4

cementum

calcified connective tissue covering the root

5

periodontal ligament

- collagen fibres linking the alveolar bone of the socket to the cementum
- rapid turnover

6

Fungiform

rounded columnar shape with TASTEBUDS

7

Filiform

jagged edges, keep the mouth clean, no tastebuds

8

circumvallate

circular, with crevices which have TASTEBUDS on the sides and food and saliva can get in

9

3 salivary glands and what they secrete

- submandibular (mixed)
- sublingual (mucous)
- parotid (serous)

10

when is saliva secreted?

following parasympathetic stimulation by seeing, smelling, tasting, or thinking about food

11

saliva =

water + mucous + enzymes

12

enzymes present in saliva

AMYLASE which breaks down starch and LYSOZYME which is antibacterial

13

4 ways of increasing surface area in the GI tract

- folds (circular and longitudinal)
- finger-like projections
- simple tubular glands
- convolutions

14

how is a steady rate of digestion maintained?

by storing food in the stomach and releasing some of its contents at intervals

15

what are the 4 tunics of the gut tube?

1. Mucosa
2. submucosa - blood, lymph, nerve
3. muscularis externa (external smooth muscle) - peristalsis
4. serosa - visceral peritoneum

16

what are the three layers of the mucous membrane (mucosa)?

1. epithelium (high turnover - for protection and absorption/secretion)
2. lamina propria - soft fibrous bed of loose connective tissue carrying nerves and blood and populated with defense cells, upon which the epithelium rests
3. muscularis mucosae - two layers of inner circular and outer longitudinal smooth muscle

17

digestion definition

chemical breakdown of ingested food into absorbable molecules

18

absorption definition

movement of nutrients, water, and electrolytes through the epithelial lining of the gut into blood or lymph

19

adventitia

outer most surface of a structure, which is not in direct contact with the body cavity

20

Oesophagus is __cm long and travels, _________ to the trachea, from the _______ to the _________.

Oesophagus is _25_cm long and travels, _posterior_ to the trachea, from the _pharynx_ to the _stomach_.

21

functions of the oesophagus

- transport: 5s for food, 1s for liquid
- protection
- no absorption, little secretion, no digestion

22

how do the four layers of the gut tube differ in the oesophagus?

- epithelium: stratified squamous, sacrificial cells for protection against abrasion. renewed every 7 days
- external muscle: contains some skeletal muscle in the upper third, for rapid contraction and voluntary control of swallowing
- NO SEROSA - fibrous adventia instead

23

stomach capacity

1.5L

24

four regions of the stomach (from the oesophagus to the duodenum)

cardia - mucous
fundus - acid, enzymes, mucous
body - acid, enzymes, mucous
pylorus - mucous

25

how do the four layers of the gut tube differ in the stomach?

- epithelium: mucous-secreting cells plus gastric glands
- external muscle: three layers (not two) with an extra innermost OBLIQUE layer

26

function of gastric folds (rugae)

- allow expansion of stomach for food
- increase surface area

27

what controls the outlet of the stomach into the duodenum?

pyloric sphincter

28

functions of the stomach

- secretion: acid, enzymes, mucous (2-3L per day)
- digestion: 20% total PROTEINS - pepsin
- absorption: water, ions, some drugs
- transport: mixing waves every 20s which produce CHYME
- protection: against its own secretions and microbes

29

how is pepsin secreted?

secreted as pepsinogen (inactive), so that it doesnt break down the stomach itself, then converted to the active pepsin form by the acid in the stomach

30

parietal cells

in the gastric gland.
secretes HCl and intrinsic factor