1. Basic digestive processes: 4 process
Digestion
Digestion is the change of complex food substances into a simpler form to be absorbed.
Basic digestive processes: 4 process
[1] Motility:
To mix & move forward the contents along the digestive tract
[2] Secretion: of
Enzymes
Mucous
electrolytes
& H2O
From
Salivary glands
Gastric glands
Intestinal glands
Pancreas
Liver
Accessory digestive system
G.B.
Exocrine
Pancreas.

2. DIGESTION
DIGESTION

3. [3] Digestion: [4] Absorption:
Breakdown of complex food substances of diet into simple Units to be absorbed.
Proteins  amino-acids
Fat  Fatty acids + Glycerol
Carbohydrate  glucose
[4] Absorption:
Transfer of the small digested units from G.I.T. into blood or lymph.

4. Alimentary canal: Is 4.5 meters in living person.
9 meters outside body.
It is a muscular tube.
Its lumen is continuous with external environment of both ends.

5. Mucosal cell layer: Submucosal layer:
Its surface is folded with ridges & valleys to  surface area.
Contains exocrine cells for secretion of enzymes & mucous.
Contains endocrine cells for secretion of hormones.
Submucosal layer:
Contains
Blood & lymph vessels.
Connective tissue.
Meissners plexus.

6. بسم الله الرحمن الرحيم

7. Muscular layer: Serosal layer: Inner Circular. to constrict diameter.
Outer Longitudinal.
to shorten length.
In between Myentric plexus.
= Auerbach’s plexus.
Myenteric plexus is connected to Meissner’s plexus.
Function: Propulsive & mixing movements.
Serosal layer:
Outer covering of G.I.T. to prevent friction with viscera
exception: esophagus & distal rectum.
Muscles of G.I.T. is Smooth except( i.e. striated):
Pharynx.
Upper 1/3 of esophagus.
External anal sphincter.
Middle 1/3 of esoph. is mixed.
Lower 1/3 is smooth.

8. Autonomous Neural Hormonal Neural Regulation
Regulation of G.I.T. functions
Autonomous
Neural
Hormonal
Neural Regulation
Enteric nervous system
= Local nerves plexuses
External autonomic nerves
Meissner’s plexus
for secretion
Myentric plexus
= Auerbach’s
for motor activity
Para. Symp.
Symp.
Vagal
Sacral

9. Enteric nervous system:
million nerve cells.
The 2 plexus are connected by interneurones.
It controls secretion & motility of G . I . T.
Cutting both symp & parasymp., both secretion & motility will continue due to the activity of enteric nervous system.
Both parasymp & symp modify (modulate, regulate) the functions of enteric n. plexus.
Autonomic control:
Nor-ep.
Relax wall
Contract sphinct.
? Secretion
Ac. ch. contract wall Relax sphincter
 Secretion
Ch. trans. effect
Postganglionic
Coeliac, sup. & inf. mesent.
Preganglionic peripheral
Fibre ganglia
Sacral (S2,3,4 pelvis nerve)
T5 – L2
Cranial (mainly vagus)
Origin
Symp.
Parasymp

10. Short Long Regulation of G.I.T. functions = Local axon reflex
Receptors either in
i.e. the components of this reflex are present in the wall of G.I.T.
Wall of G.I.T.
Outside G.I.T.
UNCONDITIONED
REFLEX
Vision
Hearing
Smell
Thinking
Centre: enteric nervous system
i.e. it is a reflex that does not reach to spinal cord or brain
CONDITIONED REFLEX

11. Types of Receptors in G.I.T.
[1] Chemoreceptors
[2] Mechanoreceptors
[3] Osmoreceptors
i.e. receptors sensitive to chemical stimuli e.g. Acid (HCL), glucose, amino-acids,Fatty acids
(Pressure receptors)
Sensitive to distension (Stretch)
Sensitive
To Osmolality inside G.I.T. e.g. Hypertonic, Hypotonic solutions
Neural Supply to bl. vessels of GIT:
[1]
[2]
[3]
N.B.: Parasymp. 
 secretion
  end products of metabolism
 V.D.
i.e. indirect
Cholinergic fibres to splanchnic bl. v.
No direct
nor-ep.
V.C.
Symp.
VIP
V.D.
Enteric n. system

12. Blood flow to mucosa > wall
After meal blood flow to G.I.T. is doubled and continue for 3 hours.
= Postprandial Hyperaemia
It is due to:
{1}  metabolism   end products  V.D.
{2}  V.D. peptides as
VIP
Bradykinin
Adenosine
CCK

13. All G.I.T. hormones are Polypeptides.
Hormonal Regulation
All G.I.T. hormones are Polypeptides.
These hormones are secreted from mucosal cells called APUD cells.
( Amine Precursor Uptake & Decarboxylation.)
these cells can take up amine precursor and decarboxylate them.
These hormones will circulate in blood.
These hormones affect ( or ) both secretion & motility of G.I.T.
These hormones are released in response. To
External autonomic nerves.
Enteric nervous system.
N.B.: Some hormones may act.
Locally i.e. not pass to blood i.e. affected nearby cells.
= Paracrine secretion.

14. Site of Release: Stimuli for release: Gastrin Hormones
G-cells in mucosa of antrum of stomach.
TG cells in mucosa of
Stomach.
Duodenum.
Mechanism: Local axons reflex.
Stimuli for release:
Products of proteins as peptides & a-a in stomach & duodenum.
Distension of the antrum of stomach & duodenum
 vagal discharge
The chemical transmitter is GRP not ac.ch.
GRP i.e. gastrin releasing peptide.
N.B.: Atropine does not prevent gastrin release  Hcl   gastrin release by direct effect on G-cells.

15. Actions of gastrin (Functions, Effects):
 Hcl secretion.
 Pepsinogen.
 gastric motility
 ileal “
Relax ileocecal sphincter
 mass movement of colon
Trophic ( growth) of stomach & S.intestine
N.B.: Zollinger Elison syndrome
Tumor in delta cells of pancreas, secretion gastrin hormone = Gastrinoma

16. Secretion hormone Site of Release:
Site of Release: S. cells of duodenum and presence of product jejunum of protein digestion and ?????.
Stimulus: Presence of Hcl in duodenum.
Mechanism: Local axon reflex.
Actions: Functions:
 secretion of NaHCO3 from duct of pancreas  to neutralize Hcl.
Choleretic i.e.  Hepatic bile 7-8 to neutralize Hcl.
 gastric Hcl
 “ motility
N.B.: Decrease gastric motility and emptying to present further acid from entering the duodenum until the acid that is already present is neutralized.
Contraction of pyloric sphincter to prevent further acid passage into duodenum (to give a chance to neutralize Hcl in duodenum.
N.B.: The effect of secretion ?????? to:
Increase alkaline pancreatic and bile juices to neutralise the acid in the duodenum that trigger ????????? there release of this hormone.

17. CCK – PZ Cholecystokinin – Pancreozymin
Site of Release:
???????????? I cells in duodenum upper brain + ??????
Stimulus:
Proteins products in duodenum
Fats in “
Action: Functions:
Contract wall of G.B. (cholagogue) & relax Oddi sphincter to digest fat.
 pancreatic secretion rich in enzymes.
 gastric motility.
 “ secretion.
Contract pyloric sphincter, till the protein & fat in duodenum are digested.
Trophic effect on pancreas.
Pancreatic juice rictin enzyme and  bile faring all blader acini ?????? if fat and plotter products in the duodenum that triggered. the release this hormone.
Gastric motility and emptying  allowing adequate time for the nutrients ??? present in the duodenum to be digested and absorbed.