Brainscape's Knowledge GenomeTM

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


See full index

Digestive System Physiology > The Digestive Tract (Overview) + Oral cavity & Oesophagus > Flashcards

The Digestive Tract (Overview) + Oral cavity & Oesophagus Flashcards

1
Q

Name the accessory glands of the digestive tract.

A

Salivary glands
Liver
Gall Bladder
Pancreas

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

Name the wall-layers of the GIT

A

Mucosa
Submucosa
Muscularis externa
Serosa

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

Discuss the MUCOSA layer of the GIT wall

A
  1. MUCOUS MEMBRANE:
    - protective surface barrier
    - epithelial cells (for absorption, also produce mucus [Goblet cells])
    - exocrine gland cells (secrete digestive juices)
    - endocrine cells (secrete GI hormones into bloodstream)
  2. LAMINA PROPRIA
    - This middle layer containing MALT
  3. MUSCULARIS MUCOSA
    - Sparse layer of smooth muscle, which upon contraction can expose different areas of surface folding
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Discuss the SUBMUCOSA layer of the GIT wall

A
  • CT (gives elasticity)
  • contains SUBMUCOSAL PLEXUS (nerve network)
  • contains larger blood & lymph vessels (branching into mucosa & muscularis layers)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Discuss the MUSCULARIS EXTERNA layer of the GIT wall

A

-Smooth m. (3 LAYERS IN STOMOACH!)

-inner circular layer
(decrease diameter on contraction)

-outer longitudinal
(decrease length on contraction)

-contains myenteric plexus

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

Discuss the SEROSA layer of the GIT wall

A
  • Outer CT secretes on a serious field (lubrication)

- Continuous with mesentry

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

What is the PRIMARY FUCTION OF THE DIGESTIVE SYSTEM?

A

TRANSFER NUTRIENTS, H20 and ELECTROLYTES (food) INTO BODY’S INTERNAL ENVIRON. (blood)

THUS, food must be broken down biochemically by DIGESTION so molecules can be ABSORBED

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

What are the functions that regulate basic digestive functions?

A
  1. MOTILITY
  2. SECRETION
  3. DIGESTION
  4. ABSORPTION
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Dicuss motility?

A

Motility = SMOOTH M. CONTRACTIONS THAT PROPEL & MIX FOOD!

  • Phasic smooth m. (AP-induced bursts of contraction)
  • Tone (constant low lvl contraction, prevents permanent distension)
  • Movement of food controlled at an appropriate VELOCITY for that part of the GIT
    (i. e. faster in oesophagus, slower in intestine [for max. possible reabsorption])

2 TYPES OF PHASIC DIGESTIVE MOTILITY:

  1. PROPULSIVE movements
    - peristalsis
  2. MIXING movements
    - segmentation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Discuss secretion?

A 
Exocrine gland cells (secrete digestive juices)
Endocrine cells (secrete GI hormones into bloodstream)

[FLUIDS & REABSORPTION]

-The digestive tract contributes liquid to the lumen
(secretory cells extract H20 & raw materials from plasma)

  • Secretions released into GI lumen by NEURAL/HORMONAL STIM.
  • Secretions reabsorbed back into blood after finishing digestive processes!
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Discuss digestion?

A

Accomplished by HYDROLYSIS of:

  • CARBS.
  • FATS
  • PROTEINS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Discuss CARB. digestion

A

Polysaccharides –>

—-> (AMYLASE - enzyme secreted in saliva & by pancreas) —->

Disaccharides –>

—-> (Enzymes [disaccaridases] on surface of intestinal absorptive cells) —->

Monosaccharides

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

Discuss PROTEIN digestion

A

EXOPEPTASE:
-Hydrolyse EXTERNAL peptide bonds found @ carboxy terminal ends
(These enzymes are found in the SI on epith. cells)

ENDOPEPTASE
-Hydrolyse INTERNAL peptide bonds
(Glandular secretions from stomach (PEPSIN) and pancreas (TRYPSIN)).

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

Discuss FAT digestion

A

STEP 1.
-Emulsification of fat droplets by bile salts

STEP 2.
-Hydrolysis of triglycerides in emulsified fat droplets into fatty acid & monoglycerides by lipases (lingual, pancreatic and gastric enzymes)

STEP 3.
-Dissolving of fatty acids & monoglycerides

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

Discuss absorption.

A

Absorption of the digested CARBS. & PROTEIN PRODUCTS:
-accomplished by Na+ dependent symport!
(both then absorbed into blood).

Absorption of the digested FAT PRODUCTS:
-a PASSIVE process!
(re-formed into lipoprotein-coated triglycerides [chylomicrons] they are reabsorbed into lymph vessels).

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

What are the factors regulating 1. MOTILITY and 2. SECRETION?

A
  1. Autonomous smooth m. function
  2. Intrinsic nerve plexuses
  3. Extrinsic nerves
  4. GI hormones
17
Q

Discuss autonomous smooth m. function.

A

GI motility derived from 2 patterns of electrical activity:

  • SLOW WAVES
  • SPIKE POTENTIALS

The membrane potential of smooth m. cells fluctuates spontaneously

Cells are electrically coupled (gap junctions), so fluctuations spread - resulting in SLOW WAVES

SPKIE POTENTIALS occur at the crest of slow waves

18
Q

What are slow waves?

A

Waves of partial depolarisation in smooth m. that sweep along with the GIT

(Not APs & do not elicit contractions by themselves, BUT they help coordinate SPIKE POTENTIALS)

19
Q

What are spike potentials?

A

APs that elicit muscle contraction.

Result when a slow wave passes over an area of smooth m. that has been primed by exposure to neurotransmitters released in their vicinity by neurons of the enteric NS
(released in response to stimuli such as distension).

20
Q

Give an example of autonomous smooth m. function.

A
  1. Bolus distends gut, stretching walls
  2. Distension stimulates nerves in gut wall to release neurotransmitters into smooth m.
    - mem. potential becomes more depolarised.
  3. When slow wave passes over this area, spike potentials form
    - contraction results
  4. Contraction moves in coordinated manner because of gap junctions.
21
Q

Discuss intrinsic nerve plexuses

A

ENTERIC NS –> SELF-REGULATION OF GUT!

  1. SUBMUCOSAL PLEXUS
    Senses luminal environment, regulating GI blood flow & controlling epithelial cell function
  2. MYENTERIC PLEXUS
    Located between circular & longitudinal layers of muscle.
    Exerts control primarily over digestive tract motility (i.e. Ach)
22
Q

Discuss extrinsic nerves

A

[Originate outside digestive syst.
Formed by ANS]

SYMPATHETIC AND PARASYMPATHETIC STIMULATION!

Sympathetic = increases motility & secretion
Parasympathetic = inhibits motility
  • influence digestive syst. by acting on intrinsic nerves, hormone secretion & effector cells
  • coordinates activity between different areas of the GIT
23
Q

Discuss GI hormones

A

Enteroendocrine cells secrete hormones into blood upon appropriate stimulation.

Travel to different regions of the GIT, where they exert excitatory & inhibitory influences on smooth m. and exocrine glands

24
Q

What occurs in the oral cavity?

A

MASTICATION
(1st step in digestive process)
=grind & break up food!
[increases food SA for salivary enzymes]

Mix with saliva

Stimulation of taste buds
(reflex increase in secretion)

25
Q

What are the components of saliva?

A

Mucus
Amylase - (break polysaccharides into maltose)
Lingual lipase - (small amount, starts fat digestion)
Lyzozome - (antibacterial)
Bicarbonate buffer - (neutralise acids)

26
Q

Name the two types of salivation reflexes.

A

Simple reflex

Conditioned reflex

27
Q

What is simple reflex salivation?

A

P and chemoreceptors in mouth (detect food) –>

Salivary centre in medulla –>
Autonomic nerves –>
Salivary glands –>
Increase salivation

28
Q

What is conditioned reflex salivation?

A

CEREBRAL CORTEX [thinking, seeing, smelling food] –>

Salivary centre in medulla –>
Autonomic nerves –>
Salivary glands –>
Increase salivation

29
Q

Discuss the oral (buccal) stage of ingestion/swallowing

A
  1. ORAL (BUCCAL) STAGE
    Voluntary phase!

-tongue pushes food portion to back of oral cavity into oropharynx by elevation & retraction against hard palate

30
Q

Discuss the pharyngeal stage of ingestion/swallowing

A
  1. PHARYNGEAL STAGE
    Involuntary phase!
  • breathing stops & airways closed
  • soft palate & uvula lift to close NASOpharynx
  • larynx elevated, vocal cords closed
  • epiglottis bent over airway as larynx is lifted
31
Q

Discuss the oesophageal stage of ingestion/swallowing.

A
  1. OESOPHAGEAL STAGE
    Involuntary phase!

-pharynx muscles contract to force bolus into oesophagus
-upper oesophageal sphincter relaxes when larynx lifted.
(closes as soon as bolus passes)
-triggers peristalsis to push food down
(circular fibres contract behind bolus to push it along)
(longitudinal fibres in front of bolus shorten the distance of travel)
-lower sphincter relaxes as food approaches

32
Q

What are the stages of ingestion/swallowing in the oral cavity?

A
  1. ORAL (BUCCAL) STAGE
  2. PHARYNGEAL STAGE
  3. OESOPHAGEAL STAGE
33
Q

What is the function of the pharyngoesophageal sphincter?

A

Prevents air entering the GIT

34
Q

What is the function of the gastroesophageal sphincter?

A

Prevents stomach contents from entering the oesophagus

35
Q

What is primary peristalsis (in the oesophagus)?

A

Preceded by the pharyngeal phase

Controlled by slowing centre (innervation from vagus)

36
Q

What is secondary peristalsis (in the oesophagus)?

A

Can occur without pharyngeal phase IF OESOPHAGUS DISTENDED

e.g. if food is stuck, P receptors trigger intrinsic nerve plexus, leading to stronger force

37
Q

What is Dysphagia

A

DISORDERED/DISTURBED EATING

can occur anywhere [whilst swallowing]

Digestive System Physiology (6 decks)

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