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Week 2 > Oes, Stomach & SI > Flashcards

Oes, Stomach & SI Flashcards

(45 cards)

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1
Q

What is the digestive system composed of?

A

1) The gastrointestinal Tract

2) Accessory Digestive Organs

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2
Q

What are the 6 digestive system processes?

A

1) Ingestion
2) Propulsion
3) Mechanical Breakdown
4) Digestion
5) Absorption
6) Deification

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3
Q

What are the 4 Basic Layers if the GIT

A

1) Mucosa: Surface epithelium, lamina proprietary and muscle layer
2) Submucosa
3) Muscularis: Longitudinal and circular layers
4) Serosa (visceral peritoneum)/ Adventitia (retroperitoneal)

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4
Q

What is the intrinsic nerve supply of the GIT?

A

Enteric Nervous System, composed of two plexus’:

1) Submucosal plexus in the submucosa layer
2) Myenteric plexus between the circular and longitudinal muscle layers

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5
Q

Differentiate a short and a long digestive reflex

A

Short Reflex: Mediated entirely by the ENS: Peristalsis

Long Reflex: ENS and CNS pathway: Full bowel, conscious decision to go to the toilet

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6
Q

What are the 3 Principles of digestive regulation?

A

1) A range of mechanical and chemical stimuli can provoke digestive activity
2) Neurons and hormones control digestive activity
3) Smooth mm and glands are the main effectors

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7
Q

What are the different parts of the oesophagus?

A
  • Cervical portion
  • Thoracic portion
  • Abdominal portion (retroperitoneal but covered anterolaterally
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8
Q

Where are the constriction points in the oesophagus?

A
  • Upper Oesophageal Sphincter: at the Pharyngoesophageal junction, caused by cricopharyngeus mm
  • Where crossed by arch of aorta
  • Where crossed by the left main bronchus
  • Lower Oesophageal Sphincter: where it passes through the diaphragm
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9
Q

Why isn’t the LOS considered a ‘true’ sphincter

A

It is a functional sphincter. Only slight muscular thickening, reinforced extrinsically by the diaphragm

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10
Q

Histology of the oesophagus

A 
Mucosa: Stratified squamous --> simple columnar at the gastroesophageal junction
Submucosa: mucous secreting glands
Muscular: 
upper 1/3: skeletal
middles 1/3 skeletal and smooth mm
lower 1/3 smooth mm
Outer layer: 
Cx and Tx part adventitia
Abdominal part: serosa
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11
Q

Arterial supply of the oesophagus

A

Arterial: branches from the inf thyroid aa, oesophageal aa, L gastric aa and L inferior phrenic aa

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12
Q

Venous supply of the oesophagus

A

Venous: inf thyroid vv, oesophageal vv –> azygous vv, left gastric vv –> portal vv

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13
Q

Lymphatic supply of the oesophagus

A

Paratracheal, inf. deep cervical, post. mediastinal nodes

Lt gastric nodes

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14
Q

Nerve supply of the oesophagus

A

Cx Portion: Recurrent laryngeal nn (branch of the CNX)
Rest of the Oesophagus:
- ENS
- Oesophageal plexus
- Parasymp: Vagus
- Symp: via the cervical sympathetic ganglia, cardiopulmonary splanchnic nns, abdominopelvic splanchnic nns (greater and lesser)
- Visceral afferent

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15
Q

What is the role of the Oesophagus

A

To propel food from the oral cavity to the stomach

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16
Q

The two phases of deglutition

A

1) Buccal Phase: voluntary
2) Pharangeal-oesophageal phase: involuntary phase
- required blockage of the epiglottis
- relaxation of the UOS
- peristaltic waves
- relaxation of the LOS

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17
Q

Functions of the Stomach

A
  • Food blender & reservoir (4L capacity)
  • Secretes gastric juices: food –> chyme
  • Secretes intrinsic factor
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18
Q

Parts of the stomach

A
  • Cardia w/ cardiac notch
  • Fundus
  • Body
  • Pylorus w/ antrum and canal
    2 curvatures
  • Lesser and greater
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19
Q

Nerve supply of the stomach

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A 
•	Intrinsic nn: ENS
•	Extrinsic nn: 
- Parasymphathetic - CNX Vagus
- Sympathetic - T6-T9 Greater splanchnic nn (through the celiac plexus)
•	Visceral afferents
20
Q

Arterial supply of the stomach

Study These Flashcards
A
  • Rich supply from branches of the celiac trunk
  • Lt gastric a. (directly off celiac trunk)- lesser curvature
  • Rt gastric a. (from common hepatic a.)- lesser curvature
  • Lt gastro-omental a. (from splenic a.)- greater curvature
  • Rt gastro-omental a. (from gastroduodenal a.)- greater curvature
  • 4-5 Short gastric aa (from splenic a.)- fundus
21
Q

Venous drainage of the stomach

Study These Flashcards
A
  • Veins run with the arteries
  • Rt & Lt gastric vv & portal v.
  • Short gastric vv & Lt gastro-omental v. & splenic v.
  • Rt gastro-omental v. & SMV
  • SMV & splenic v. unite to form portal v.
22
Q

Lymphatic drainage of the stomach

Study These Flashcards
A
  • Vessels run with the arteries

* Gastric & gastro-omental nodes à celiac nodes

23
Q

Longitudinal ridges that allow the stomach to expand

24
Q

The GIT is lined with two muscular layers, what is the additional layer in the stomach,?

Study These Flashcards
A

Oblique layer- as well as longitudinal and circular

25
What cells are found in the gastric pit
1) Mucous (Neck) Cells 2)Parietal Cells: secrete HCl for enzyme activation & intrinsic factor for vic B12 absorption 3) Cheif Cells: Pepsinogen & Gastric lipase 4) Enteroendocrine Cells: ie G Cells for Gastrin Enterochromaffin Cells for histamine serotonin (for contractility)
26
What is the role of the stomach?
- Mechanical breakdown and propulsion - Digestion: pepsinogen and gastric lipase - Absorption: fat soluble substances ie alcohol, aspirin Other Roles: - Food reservoir - HCl -Intrinsic Factor
27
How is HCl produced?
Stimulated by: - ACh (from vagus parasympathetic) - Histamine - Gastrin Parietal Cell: CO2 + H2O H2CO3 (dissociates into) H+ & HCO3 H+ is pumped out of cell by H+/K+ ATPase proton pump H+ & Cl- bind in the lumen of the stomach to make HCl
28
What is the enterogastric reflex?
- The reflex is stimulated by a low pH in either the duodenum or the stomach and distention of the duodenum - The enterogastric reflex causes reflex inhibition of ENS and vagus nerve so that secretion and motility decrease
29
what are the two mechanisms of gastric emptying?
1) Enterogastric Reflex - Duodenal receptors are stimulated by distention and change in pH - Vagus and ENS stop secretion and motility 2) Duodenal hormones released in response to fatty acidic chyme: • Cholecystokinin: stimulates the release of bile into the intestine and the secretion of enzymes by the pancreas • Gastric Inhibitory Peptide • Secretin: stimulates pancreas and liver
30
What are some Cephalic factors that regulate gastric activity?
``` STIMULATE 1) Sight and thought of food 2) Stimulation of taste and smell receptors INHIBIT 1) Loss of appetite ie depression ```
31
What are some Gastric factors that regulate gastric activity?
STIMULATE 1) Stomach distention activates stretch receptors 2) Chemicals from food ie peptides and caffeine 3) Rise in pH from food INHIBIT 1) Excessive acidity 2) Emotional stress
32
What are some Duodenal/ Intestinal factors that regulate gastric activity?
STIMULATE 1) Presence of partially digested food 2) Distension of duodenum from gastric emptying INHIBIT 1) Presence of fatty, acidic or hypertonic chyme 2) Irritants in the duodenum ie H. Pylori
33
What is the function of the Small Intestine (SI)/ Bowel
- Receives secretions from the liver/ pancreas - Mechanical & chemical digestion; absorption of nutrients - Transportation of undigested material to large intestine
34
What is the nerve supply of the duodenum?
- Intrinsic: ENS - Sympathetic: Greater & lesser splanchnic nn (T5-9) via the celiac & sup. mesenteric plexuses - Parasympathetic: Vagus N - Visceral Afferents
35
What is the vascular supply of the duodenum?
Arterial Supply - Gastroduodenal a. (common hepatic a., off celiac trunk) - Sup. pancreaticoduodenal aa (common hepatic a., off celiac trunk) - Inf. pancreaticoduodenal aa (SMA) Venous Supply - Duodenal V follow aa- drains into the portal v. Lymphatic Supply - Pancreaticoduodenal nodes - Sup. mesenteric nodes
36
What part of the duodenum is intraperitoneal?
Only D1 (Maybe a bit of D2) the rest of the duodenum is retro-peritoneal
37
What quadrants do most of the jejune and ileum sit?
Jejunum: LUQ Ileum: RLQ
38
What is the nerve supply of the jejunum and ileum?
- Intrinsic: ENS - Parasympathetic: Vagus N - Sympathetic: Greater & Lesser splanchnic nn (T5-9) via the celiac & sup. mesenteric plexuses - Visceral afferents
39
What is the arterial supply of the jejunum and ileum?
- SMA provides 15 -18 branches (run between layers of the mesentery)
40
What is the venous supply of the jejunum and ileum?
- SMV – unites with splenic v. to form portal v.
41
What is the lymphatic supply of the jejunum and ileum?
Sup. mesenteric nodes
42
What are the factors that make the SI specialised for absorption?
1) Circular Folds: The mucosa & submucosa are arranged in permanent folds that force chyme to spiral through lumen 2) Villi: In the core of each villus there is a dense capillary bed and a lymphatic capillary (lacteal) 3) Microvilli: They are cytoplasmic extensions of mucosal absorptive cells that have brush border enzymes (embedded in membrane) to perform the final digestion of food
43
What are the specialised cells in the villi and Crypts?
1) Enterocyte: Absorptive cells endowed with microvilli- Crypt enterocytes secrete intestinal juice 2) Goblet Cells: Produce alkaline mucous (relies on PGE2) 3) Enteroendocrine Cells: secretes enterogastrones (hormones) like CCK and secretin 4) Paneth Cells: release antimicrobial agents (lysozymes) 5) Stem Cells: Renew the epithelium every 3-5 days
44
What is the role of the SI?
Mechanical breakdown and propulsion - Involved in segmentation and peristalsis Digestion - Digestive enzymes delivered from pancreas - Brush border enzymes embedded in microvilli membranes - Bile produced by liver emulsifies fats & enhances digestion Absorption - Breakdown products of CHO, protein, fat & nucleic acid digestion - Water, vitamins, electrolytes
45
What duodenal hormones are released in response to gastric emptying?
- Gastric inhibitory peptide - Cholecystokinin - Secretin

Week 2 (2 decks)

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