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 Salivary glands Liver G.B. Exocrine Pancreas.

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 Salivary glands Liver G.B. Exocrine Pancreas.

[3] Digestion:Breakdown of complex food substances of diet

into simple Units to be absorbed.Proteins amino-acidsFat Fatty acids + GlycerolCarbohydrate glucose

[4] Absorption:Transfer of the small digested units from G.I.T.

into blood or lymph.

[3] Digestion:Breakdown of complex food substances of diet

into simple Units to be absorbed.Proteins amino-acidsFat Fatty acids + GlycerolCarbohydrate glucose

[4] Absorption:Transfer of the small digested units from G.I.T.

into blood or lymph.

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.

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.

1.Mucosal cell 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.

2.Submucosal layer: Contains

Blood & lymph vessels. Connective tissue. Meissners plexus.

1.Mucosal cell 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.

2.Submucosal layer: Contains

Blood & lymph vessels. Connective tissue. Meissners plexus.

3.Muscular 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.

4.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):

1. Pharynx. 2. Upper 1/3 of esophagus. 3. External anal sphincter.

Middle 1/3 of esoph. is mixed. Lower 1/3 is smooth.

3.Muscular 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.

4.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):

1. Pharynx. 2. Upper 1/3 of esophagus. 3. External anal sphincter.

Middle 1/3 of esoph. is mixed. Lower 1/3 is smooth.

Autonomous Autonomous Neural Neural HormonalHormonal

Neural RegulationNeural RegulationEnteric nervous system= Local nerves plexusesEnteric nervous system= Local nerves plexuses

Meissner’s plexus

for secretion

Meissner’s plexus

for secretion

Myentric plexus Myentric plexus = Auerbach’s = Auerbach’s for motor activity for motor activity

Myentric plexus Myentric plexus = Auerbach’s = Auerbach’s for motor activity for motor activity

External autonomic nerves External autonomic nerves

Para. Symp. Para. Symp. Symp. Symp. Symp. Symp.

Vagal Vagal Sacral Sacral

Enteric nervous system: 80-100 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.

Enteric nervous system: 80-100 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:Autonomic control:

Nor-ep.Relax wall

Contract sphinct. ? Secretion

Nor-ep.Relax wall

Contract sphinct. ? Secretion

Ac. ch. contract wall Relax sphincter

Secretion

Ac. ch. contract wall Relax sphincter

Secretion

Ch. trans. effectCh. trans. effect

PostganglionicCoeliac, sup. & inf. mesent.

PostganglionicCoeliac, sup. & inf. mesent.

Preganglionic peripheralPreganglionic peripheralFibre gangliaFibre ganglia

Sacral (S2,3,4 pelvis nerve)Sacral (S2,3,4 pelvis nerve)

T5 – L2 T5 – L2

Cranial (mainly vagus)Cranial (mainly vagus)OriginOrigin

Symp.Symp.ParasympParasymp

Short Short Long Long = Local axon reflex = Local axon reflex Receptors either in Receptors either in

i.e. the components of this reflex are present in the wall of G.I.T. i.e. the components of this reflex are present in the wall of G.I.T.

Centre: enteric nervous system i.e. it is a reflex that does not

reach to spinal cord or brain

Centre: enteric nervous system i.e. it is a reflex that does not

reach to spinal cord or brain

Wall of G.I.T. Wall of G.I.T.

UNCONDITIONED REFLEX

UNCONDITIONED REFLEX

Outside G.I.T. Outside G.I.T.

Vision Hearing

Smell Thinking

Vision Hearing

Smell Thinking

CONDITIONED REFLEX

CONDITIONED REFLEX

[1] Chemoreceptors [1] Chemoreceptors [2] Mechanoreceptors [2] Mechanoreceptors [3] Osmoreceptors [3] Osmoreceptors

i.e. receptors sensitive to chemical stimuli e.g. Acid (HCL), glucose, amino-

acids,Fatty acids

i.e. receptors sensitive to chemical stimuli e.g. Acid (HCL), glucose, amino-

acids,Fatty acids

(Pressure receptors)Sensitive to distension

(Stretch)

(Pressure receptors)Sensitive to distension

(Stretch)

Sensitive To Osmolality inside

G.I.T. e.g. Hypertonic, Hypotonic solutions

Sensitive To Osmolality inside

G.I.T. e.g. Hypertonic, Hypotonic solutions

Types of Receptors in G.I.T.Types of Receptors in G.I.T.

Neural Supply to bl. vessels of GIT:Neural Supply to bl. vessels of GIT:

[2][2] [3][3][1][1]

N.B.: Parasymp. secretion

end products of metabolism

V.D.i.e. indirect

N.B.: Parasymp. secretion

end products of metabolism

V.D.i.e. indirect

Cholinergic fibres to splanchnic bl. v.Cholinergic fibres to splanchnic bl. v.

No directNo direct

nor-ep.

V.C.

nor-ep.

V.C.

Symp.Symp.

VIPV.D.VIPV.D.

Enteric n. systemEnteric n. system

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

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

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

1. External autonomic nerves.

2. Enteric nervous system.

N.B.: Some hormones may act.

Locally i.e. not pass to blood i.e. affected nearby cells.

= Paracrine secretion.

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

1. External autonomic nerves.

2. Enteric nervous system.

N.B.: Some hormones may act.

Locally i.e. not pass to blood i.e. affected nearby cells.

= Paracrine secretion.

Site of Release:1. G-cells in mucosa of antrum of stomach.

1. TG cells in mucosa of Stomach. Duodenum.

2. Mechanism: Local axons reflex.

Site of Release:1. G-cells in mucosa of antrum of stomach.

1. TG cells in mucosa of Stomach. Duodenum.

2. Mechanism: Local axons reflex.

Stimuli for release:1. Products of proteins as peptides & a-a in stomach & duodenum. 2. Distension of the antrum of stomach & duodenum33 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.

Stimuli for release:1. Products of proteins as peptides & a-a in stomach & duodenum. 2. Distension of the antrum of stomach & duodenum33 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.

Actions of gastrin (Functions,

Effects):33 Hcl secretion.

33 Pepsinogen.

33 gastric motility

33 ileal “

5. Relax ileocecal sphincter

33 mass movement of colon

7. Trophic ( growth) of stomach

& S.intestine

N.B.: Zollinger Elison syndrome

Tumor in delta cells of pancreas,

secretion gastrin hormone =

Gastrinoma

Actions of gastrin (Functions,

Effects):33 Hcl secretion.

33 Pepsinogen.

33 gastric motility

33 ileal “

5. Relax ileocecal sphincter

33 mass movement of colon

7. Trophic ( growth) of stomach

& S.intestine

N.B.: Zollinger Elison syndrome

Tumor in delta cells of pancreas,

secretion gastrin hormone =

Gastrinoma

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:

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:

33 secretion of NaHCO3 from duct of pancreas to neutralize Hcl.

2. Choleretic i.e. Hepatic bile 7-8 to neutralize Hcl.

33 gastric Hcl 33 “ motility

33 secretion of NaHCO3 from duct of pancreas to neutralize Hcl.

2. Choleretic i.e. Hepatic bile 7-8 to neutralize Hcl.

33 gastric Hcl 33 “ 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.

N.B.: Decrease gastric motility and emptying to present further acid from entering the duodenum until the acid that is already present is neutralized.5. Contraction of pyloric sphincter to prevent further acid passage into duodenum (to

give a chance to neutralize Hcl in duodenum.5. 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.

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.

Site of Release: ???????????? I cells in duodenum upper brain + ??????

Stimulus: Proteins products in duodenum Fats in “

Action: Functions:

Site of Release: ???????????? I cells in duodenum upper brain + ??????

Stimulus: Proteins products in duodenum Fats in “

Action: Functions:

1. Contract wall of G.B. (cholagogue) & relax Oddi sphincter to digest fat.

33 pancreatic secretion rich in enzymes.

33 gastric motility.33 “ secretion.5. Contract pyloric sphincter, till the

protein & fat in duodenum are digested.

6. Trophic effect on pancreas.

1.Contract wall of G.B. (cholagogue) & relax Oddi sphincter to digest fat.

33 pancreatic secretion rich in enzymes.

33 gastric motility.33 “ secretion.5.Contract pyloric sphincter, till the

protein & fat in duodenum are digested.

6.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.

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.