DIGESTIVE SYSTEM

OVERVIEW OF DIGESTIVE SYSTEMdis = apart

gerere = to carry

The digestive system consists of a group of organs that break down the food we eat into smaller molecules that can be used by body cells.

Two groups of organs compose the digestive system:

1. Gastrointestinal tract or alimentary canal ( alimentary = nourishment )

2. Accessory digestive organs

The length of the gastrointestinal tract is about 5 to 7 meters ( 16.5 – 23 ft ) in a living person when the muscles along the wall of the GI tract organs are in a state of tonus ( sustained contraction )

It is longer in cadaver ( about 7 to 9 meters or 23 – 29.5 ft ) because of the loss of muscle tone after death.

NASAL CAVITY

ORAL CAVITY

LARYNX

NASOPHARYNX

tongue

OROPHARYNX

LARYNGOPHARYNX

Epiglottis

Oesophagus

TracheaVocal cords

Palate

Auditory tube

opening

Palatine tonsil

DEVELOPMENT

ECTODERM :Epithelial lining of oral cavity, lower part of anal canal

Enamel of teeth

ENDODERM : Epithelial lining of gastrointestinal tract

Liver ( hepatocytes )

Pancreas ( acinar and islet cells )

HUMAN DIGESTIVE SYSTEM

ALIMENTARY CANAL ACCESSORY DIGESTIVE

ORGAN

MOUTH

PHARYNX - 12 TO 14 CM / 3.5 CM 1.5 CM

OESOPHAGUS – 25 CM / 2 CM

STOMACH – 25 CM / 30- 50ml ,1000- 1500 ml

SMALL INTESTINE

LARGE INTESTINE

SALIVARY GLANDS

LIVER – 1.4 kg

PANCREAS

GASTRIC GLANDS

INTESTINAL GLANDS

GALL BLADDER

8.3 mts from mouth

To anus

SMALL INTESTINE – 6.5 METRES/ 20 FEET

DUODENUM – 25 CM / 5 CM

JEJUNUM – 8 FEET/ 4 CM

ILEUM - 12 FEET / 3.5 CM

LARGE INTESTINE

1.CAECUM AND APPENDIX

CAECUM – 6 CM / 7.5 CM

APPENDIX – 2 TO 20 CM / 2.1 MM

2. COLON

ASCENDING – 15 CM / 5 CM

TRANSVERSE COLON – 50 CM / 5 CM

DESCENDING COLON – 25CM / 3.5 CM

SIGMOID COLON - 40 CM / 3.5 CM

3. RECTUM - 12 CM / 4 CM

4. ANAL CANAL – 3.8CM

FUNCTIONS OF DIGESTIVE SYSTEM

1.INGESTION : taking food and liquids into the mouth

2.SECRETION : cells within the walls of gi tract and accessory digestive organs secrete a total of 7 litres of water, acid, buffers, and enzymes into the lumen of tract

3.MOTILITY : alternating contractions and relaxations of smooth muscle in the walls of the gi tract mix food and secretions and move them toward anus

4.DIGESTION: is the process of breaking down ingested food into small molecules that can be used by body cells.

MECHANICAL DIGESTION CHEMICAL DIGESTION

5. ABSORPTION: the movement of the products of digestion from the lumen of the GI tract into bloodor lymph is called absorption. Whereas, vitamins,ions,cholesterol and water are absorbed without undergoing digestion

6.DEFECATION: elimination of feces from GI tract

LAYERS OF GI TRACTTHE WALL OF THE GI TRACT FROM THE LOWER OESOPHAGUS TO THE ANAL CANAL HAS THE

SAME BASIC, FOUR LAYERED ARRANGEMENT OF TISSUES.

THE 4 LAYERS OF TRACT FROM DEEP TO SUPERFICIAL ARE:

1. MUCOSA

2. SUBMUCOSA

3. MUSCULARIS EXTERNA

4. SEROSA/ ADVENTITIA

LUMEN

MUCOSA

IT IS THE INNER LINING OF THE GI TRACT. IT IS A MUCOUS MEMBRANE. IT CONSISTS OF

1. EPITHELIUM

2. LAMINA PROPRIA

3. MUSCULARIS MUCOSAE

1.EPITHELIUM

Non keratinised stratified squamous epithelium: mouth, pharynx,oesophagus and anal canal

Simple columnar epithelium: stomach to intestine and gall bladder

Functions in secretion and absorption

Tight junctions are present, hence prevent leakage between cells

Rate of renewal of cells: every 5 to 7 days

Located among the epithelial cells are exocrine cells that secrete mucus and fluid into the lumen of the tract

Also located among epithelial cells are several type of endocrine cells, collectively called enteroendocrine cells which secrete hormones.

2.LAMINA PROPRIA:

It is areolar connective tissue

Contains many blood and lymph vessels,which are the routes by which nutrients absorbed into the GI tract reach the other tissues of the body

Lamina propria also contains MALT ( mucosa associated lymphatic tissue ).

These lymphatic nodules contain immune system cells that protects against desease.

3.MUSCULARIS MUCOSAE:

IT IS A THIN LAYER OF SMOOTH MUSCLE FIBRES, THROWS THE MUCOUS MEMBRANE OF THE STOMACH AND INTESTINE INTO MANY FOLDS,WHICH INCREASE THE SURFACE AREA FOR DIGESTION AND ABSORPTION.

SUBMUCOSA

Consists of areolar connective tissue

Contains many blood vessels and lymphatic vesselsthat receive absorbed food molecules

It contains extensive network of neurons known as submucosal plexus

Submucosa may also contain glands and lymphatic tissue

MUSCULARIS EXTERNA

Skeletal muscle: is found in mouth, pharynx,upper and middle part of oesophagus, external anal sphincter

Smooth muscle: found in rest of gi tract.

They are arranged as 2 sheets, inner circular and outer longitudinal. In stomach there is an additional oblique layer.

Involuntary contractions of smooth muscle help break down food, mix it with digestive secretions, and propel it along the tract.

Between the layers of the muscularis is second plexus of neurons – the myenteric plexus

SEROSA / ADVENTITIA

Serosa ( visceral peritoneum ) is a serous membrane composed of areolar coonective tissue and simplesquamous epithelium ( mesothelium )

If a organ is not covered by peritoneum, but instead only a single layer of areolar connective tissue, then it is called as adventitia.

NEURAL INNERVATION OF THE GI TRACT

INTRINSIC SET OF NERVES EXTRINSIC SET OF NERVES

( ENTERIC NERVOUS SYSTEM) AUTONOMIC NERVOUS SYSTEM )

( BRAIN OF THE GUT )

EXTENDS FROM OESOPHAGUS TO THE ANUS

ENTERIC NERVOUS SYSTEM (ENS)

MYENTERIC PLEXUS/

AUERBACH PLEXUS MEISSNER PLEXUS/

SUBMUCOSAL PLEXUS

ARRANGED IN

TWO PLEXUSES

LOCATED BETWEEN THE LONGITUDINAL

AND CIRCULAR SMOOTH MUSCLE LAYER

LOCATED WITHIN

THE SUBMUCOSA

PLEXUSES OF ENS CONTAINS MOTOR NEURONS

INTERNEURONS ( INTERCONNECT BOTH THE PLEXUS)

SENSORY NEURONS

THIS PLEXUS CONTROLS GI TRACT MOTILITY THIS PLEXUS CONTROLS SECRETIONS

THE SENSORY NEURONS OF ENS SUPPLY THE MUCOSAL EPITHELIUM AND CONTAIN

RECEPTORS THAT DETECT STIMULI IN THE LUMEN OF GI TRACT

THE WALL OF THE GI TRACT CONTAINS TWO MAJOR TYPES OF SENSORY RECEPTORS

CHEMORECEPTORS MECHANORECEPTORS

RESPOND TO CERTAIN CHEMICALS IN FOOD IN LUMEN ARE ACTIVATED WHEN FOOD

DISTENDS THE WALL OF GI

AUTONOMIC NERVOUS SYSTEMGIT

NEURONS OF ENS CAN FUNCTION INDEPENDENTLY

BUT THEY ARE REGULATED BY NEURONS OF AUTONOMIC NERVOUS SYSTEM

PARASYMPATHETIC NERVOUS SYSTEM SYMPATHETIC NERVOUS SYSTEM

VAGUS NERVE ( TILL TRANSVERSE COLON)

S2, S3,S4 FOR REST OF COLON BEYOND TRANSVERSE

COLON

FUNCTIONS BY INCREASING THE GI SECRETION AND MOTILITY

BY INCREASING THE ACTIVITY OF ENS NEURONS

SUPPLIED BY

THORACO LUMBAR OUTFLOW (T1 TO L2)

FUNCTIONS BY DECREASING THE

GI SECRETION AND MOTILITY BY

INHIBITING THE NEURONS OF ENS

SUPPLIED BY

EMOTIONS SUCH AS ANGER,FEAR,AND ANXIETY MAY SLOW DIGESTION BECAUSE

THEY STIMULATE SYMPATHETIC NERVES.

SURFACE MODIFICATION OF SMALL INTESTINE

PLICAE

CIRCULARES

VILLI

MICROVILLI

SURFACE MODIFICATION OF SMALL INTESTINE

PLICAE CIRCULARIS

Permanent spiral folds

Elevation of mucosa with a submucosal core

SURFACE MODIFICATION OF SMALL INTESTINEVILLI ( tufts of hair)

PERMANENT FINGERLIKE PROJECTIONS OF

LAMINA PROPRIA OF MUCOSA THAT EXTEND INTO LUMEN

COVERED BY SIMPLE COLUMNAR EPITHELIUM

HAS A CORE OF LAMINA PROPRIA ( CONTAINS ARTERIOLE, A VENULE,

A BLOOD CAPILLARY NETWORK AND A LACTEAL

LABEL THE PARTS

SURFACE MODIFICATION OF SMALL INTESTINEMICROVILLI ( gives a brush border appearance )

Cytoplasmic extensions that cover the apices of intestinal absorptive cells.

CELLS ,GLANDS ,LYMPHATIC NODULESOF SMALL INTESTINE

INTESTINAL GLANDS OF LIEBERKUHN

CELLS ,GLANDS ,LYMPHATIC NODULESOF SMALL INTESTINE

CELLS

Absorptive cells (columnar)

Goblet cells

Enteroendocrine or apud cells

Undifferentiated cells

Paneth cells

CELLS ,GLANDS ,LYMPHATIC NODULESOF SMALL INTESTINE

PEYERS PATCHES

NUMEROUS AGGREGATIONS OF CLOSELY

PACKED ,PERMANENT LYMPHATIC NODULES

ILEUM

Payers patches

HISTOLOGY OF ORAL CAVITY

TONGUEPapillae are lined by

Stratified squamous nonkeratinized

Epithelium , except filiform papillae

Which is lined by stratified squamous

Keratinised epithelium to grasp food on tongue.

SEROUS SALIVARY GLAND

MUCOUS SALIVARY GLAND

MIXED SALIVARY GLAND

HISTOLOGY OF GASTRO INTESTINAL

TRACT

OESOPHAGUS

STOMACH FUNDUS

STOMACH PYLORUS

DUODENUM

JEJUNU

ILEUM

LARGE INTESTINE

APPENDIX

MOUTH

MOUTH

ORAL CAVITY\

BUCCAL CAVITY

LIPS

CHEEKS

ORBICULARIS ORIS MUSCLE

Present around oral fissure

HARD PALATE

SOFT PALATE

UVULA ( VELUM

PALATI )

TONGUE

LINED BY MUCOUS MEMBRANE – Stratified squamous nonkeratinized

epithelium.

Palate helps to chew and breathe at the same time

During swallowing , the soft palate and uvula are drawn up, closing off

the nasopharynx and preventing swallowed foods and liquids from

entering the nasal cavity.

VESTIBULE ( SPACE BETWEEN

GUMS AND CHEEKS )

TONGUE

THICK MUSCULAR ORGAN

( skeletal muscle )

FRENULUM

SHORT FRENULUM ( ANKYLOGLOSSIA)

TONGUE TIED

TONGUE - FUNCTIONS

DEGLUTITION EXPRESSIONS

MASTICATION

SPEECH

TASTE

TONGUE IS CONNECTED TO 3 BONES

BY MUSCLES.

STYLOGLOSSUS MUSCLE

HYOGLOSSUS MUSCLE

GENIOGLOSSUS MUSCLE

STYLOID PROCESS

MANDIBLE

HYOID BONE

ORAL PART

( ANTERIOR 2/3RD)

PHARYNGEAL PART

( POSTERIOR 1/3RD )SULCUS TERMINALIS

FORAMEN CAECUM

TONGUEMUCOUS MEMBRANE OF ANTERIOR 2/3RD PRESENTS CONICAL

PROJECTIONS CALLED PAPILLAE

THEY ARE 4 TYPES

EPIGLOTTIS

LINGUAL TONSIL

PALATINE TONSIL

CIRCUMVALLATE PAPILLAE (taste buds)RECEPTORS FOR GUSTATION

FILIFORM PAPILLAE

FOLIATE PAPILLAE

FUNGIFORM PAPILLAE ( taste buds )

LINGUAL GLANDS OF TONGUE ( VON EBNER )

SECRETE SEROUS AND MUCOUS FLUID

WHICH CONTAIN THE ENZYME LINGUAL LIPASE

DIETARY TRIGLYCERIDES

SIMPLER FATTY ACIDS AND DIGLYCERIDES

LINGUAL LIPASE

CIRCUMVALLATE PAPILLAE : large, 8 to 12 in number, arranged in front of

sulcus terminalis, presents taste buds.

FUNGIFORM PAPILLAE: reddish / pinkish in colour, contain taste buds

FOLIATE PAPILLAE: present around margins of tongue

contain taste buds

prominent in rabbits

FILIFORM PAPILLAE: Numerous,THEY HAVE NO TASTE BUDS. Lined by

stratified squamous keratinized epithelium.

Note: all other papillae are lined by stratified squamous non keratinized

epithelium

TASTE BUDS (gustatory = taste )

THEY ARE MODIFICATIONS OF EPITHELIA

Taste buds are present in the epithelia of

1. tongue

2. soft palate

3. epiglottis

4. oropharynx

Each taste bud is made up of

1. gustatory sensory cells

2. supporting cells

Each bud opens on the surface of the epithelium by an aperture

Known as GUSTATORY PORE/ TASTE PORE, microvilli project

from the same. Base of the bud is penetrated by gustatory nerves.

MUCOUS MEMBRANE OF POSTERIOR 1/3RD PRESENTS LYMPHATIC TISSUE

LINGUAL TONSIL

TONGUE

INFERIOR SURFACE

FRENULUM LINGUAE

SUBLINGUAL PAPILLA

SUBMANDUBULAR DUCT

SUBLINGUAL PAPILLA

INFERIOR SURFACE

PLICA FIMBRIATA

PROFUNDA LINGUAE VEIN

PAROTID GLAND

PAROTID GLAND

( STENSON’S DUCT )

UPPER SECOND ( MAXILLARY0MOLAR TOOTH

SUBMANDIBULAR GLAND OR

SUBMAXILLARY GLAND

( WHARTON’S DUCT )

SUBLINGUAL GLAND( DUCT OF RIVINUS / BARTHOLIN’S

DUCT )

SALIVARY GLANDS

( EXOCRINE GLAND )

ON THE SIDE OF FRENULUM OF TONGUE

ON SMALL PAPILLAE BENEATH THE TONGUE

OPENS

OPENS

OPENS

OPENS

PAROTID GLAND SUBMANDIBULAR GLAND

MEDIUM SIZED GLAND

FOUND IN THE FLOOR OF THE MOUTH ( medial and partly below the mandible)

MUCOUS FLUID WITH SALIVARY AMYLASE

LARGEST SALIVARY GLAND

LOCATED BELOW AND FRONT OF THE EARS

SEROUS FLUID

ENZYME SALIVARY AMYLASE OR PTYALIN

SUBLINGUAL GLAND

LIE BENEATH THE TONGUE

SMALLEST SALIVARY GLAND

MUCOUS WITH LITTLE SALIVARY AMYLASE

MINOR SALIVARY GLANDS( LOCATED IN THE MUCOUS MEMBRANE OF MOUTH AND TONGUE )

LABIAL GLANDS

BUCCAL GLANDS

PALATAL GLANDS

LINGUAL GLANDS

Mucous secreting minor

Or accessory glands are

Unicellular goblet cells,

Nuhn’s gland and weber’s

gland

Weber’s gland clear the peritonsillar space of debris

CHLORIDE IONS IN SALIVA ACTIVATE SALIVARY AMYLASE

STARCH MALTOSE + MALTOTRIOSE + α DEXTRIN

PH OF SALIVA – 6.35- 6.85 ( bicarbonate and phosphate ions

buffer acidic foods )

REMOVES WASTE PRODUCTS – UREA, URIC ACID

NORMAL SALIVA : 1000 - 1500 ML.

LINGUAL LIPASE WORKS IN THE ACIDIC ENVIRONMENT OF THE STOMACH

AND THUS STARTS TO WORK AFTER FOOD IS SWALLOWED.

STOMACH ACID INACTIVATES SALIVARY AMYLASE

CHLORIDE

SALIVARY AMYLASE

TEETH ( in human, teeth are attached to maxilla and

mandible bone )

PARTS OF TOOTH

ROOT

CROWN

NECK

GUMS

JAW BONE

Teeth lie in the alveolar socket ( of maxilla and mandible bone).

Sockets are lined by periodontal ligament which consists of dense fibrous

connective tissue that anchors the teeth to socket wall and act as

shock absorber during chewing.

APICAL FORAMEN

INTERIOR OF TOOTH

COVERED BY THREE CALCIFIED TISSUES

DENTINE

ENAMEL

CEMENTUM DISINTEGRATION OF ONE OR MORE OF DENTAL

TISSUES IS CALLED AS CARIES

Lined by single layer of tall columnar cells called

As ODONTOBLAST

ODONTOBLAST --- PRODUCE DENTINE THROUGHOUT LIFE

AMELOBLASTS --- PRODUCE ENAMEL, NOT PRODUCED THROUGHOUT LIFE,

ONCE DAMAGED, IT CANNOT REGENERATE.

CEMENTOBLAST - PRODUCES CEMENTUM

Ossein is the protein of bone

DENTINE ENAMEL CEMENTUM

DEVELOPS FROM MESODERM

DEVELOPS FROM ECTODERM

DEVELOPS FROM MESODERM

FORMS BULK OF TOOTHHARD , ELASTIC, YELLOWISH WHITEAVASCULAR

HARDEST CALCIFIED TISSUECOVERS CROWN OF TOOTH

CALCIFIED TISSUECOVERS ROOT OF TOOTH.SHARPEY’S FIBRES ANCHOR A TOOTH TO THESURROUNDING BONE.

HARDER THAN BONES BECAUSE OF HIGH CONTENT OF HYDROXYAPATITE.

PROCESS OF DENTINE FORMATION PERSISTSTHROUGOUT LIFE

Consists of calciumphosphate and calcium carbonate

Not synthesized throughout Life, once damaged cannotRegenerate.

ENAMEL IS THE HARDEST SUBSTANCE IN THE BODY

CLASSIFICATION OF TEETH

DECIDUOUS TEETH PERMANENT TEETH

ALL MAMMALS ARE DIPHYODONTY ( POSSESS TWO DENTITIONS )

RAT AMONGST MAMMALS,

IS AN EXCEPTION AND IS A

MONOPHYODONT.

MILK TEETH/ PRIMARY TEETH

20 IN NUMBER

DENTAL FORMULA; 2,1,2

2 INCISORS,1 CANINE, 2 MILK MOLARS

32 IN NUMBER

DENTAL FORMULA ; 2,1,2,3

2 INCISORS,1 CANINE,

2 PREMOLARS ,3 MOLARS

THE FIRST FIVE TEETH ARE

SUCCESSIONAL

MOLAR TEETH ARE

ACCESSIONAL TEETHNO TEETH ARE PRESENT AT BIRTH

1ST TOOTH TO ERUPT - LOWER MEDIAL INCISOR ( 6TH TO 8 TH MONTH )

BY END OF 2ND YEAR , THE ERUPTION OF DECIDUOUS TEETH IS COMPLETE.

AT 6TH YEAR, THE FIRST PERMANENT MOLAR TEETH ERUPT IN BOTH JAWS --- 6TH

YEAR MOLAR

2nd molar – 12th year molar

3rd molar ( wisdom ) - 18th and 25th year or fails to erupt.

Due to the activity of osteoclast cells, milk teeth are shed and permanent teeth will appear

PHARYNX

PHARYNX

EXTENT:BASE OF THE SKULL TO C6 VERTEBRA

FUNCTION:CHANNEL FOR FOOD

AIR THROUGH NASOPHARYNX

AIR & FOOD THROUGH OROPHARYNX AND LARYNGOPHARYNX

MEASUREMENTS:

LENGTH: 12 TO 14CMS.

WIDTH:

NASOPHARYNX (3.5CM)PHARYNGO-OESOPHAGEAL JUNCTION (1.5CM).

NASOPHARYNX

BEHIND THE NOSE.

OROPHARYNX

BEHIND THE ORAL CAVITY

LARYNGOPHARYNX

BEHIND THE LARYNX.

PARTS:

WHEN WE SWALLOW , THE TOP OF THE WINDPIPE MOVES UP SO

THAT ITS OPENING, THE GLOTTIS , IS BLOCKED BY A CARTILAGINOUS FLAP,

THE EPIGLOTTIS

EPIGLOTTIS

PHARYNX

Nasopharyngeal tonsil

Tubal tonsil

Palatine tonsil

Auditory tube

EAR --- PARTS

EXTERNAL EAR

MIDDLE EAR

INTERNAL

EAR

AUDITORY TUBE

TYMPANIC MEMBRANE

MIDDLE EAR

PALATINE TONSIL

TUBAL TONSIL

PHARYNGEAL TONSIL

LINGUAL TONSIL

ADENOIDSEnlargement of nasopharyngeal tonsil is called as adenoids

These enlarged tonsils may cause obstruction in normal breathing

ADENOID FACIES

OESOPHAGUS ( 25 CM LONG / 1.5 cm to 2 cm in width)

PHARYNX

STOMACH

OESOPHAGUS

Muscular canal

OESOPHAGUS

oesophagus

CRICOID CARTILAGE

OESOPHAGUS

T 10 ( PIERCES DIAPHRAGM)

T 11 (OPENS INTO STOMACH)

PHARYNX

STOMACH

T5

T7

BEGINS AT THE LEVEL OF

DIAPHRAGM

UPPER OESOPHAGEAL SPHINCTER : CONSISTS OF SKELETAL MUSCLE

LOWER OESOPHAGEAL SPHINCTER: CONSISTS OF SMOOTH MUSCLE

OESOPHAGUS SECRETES MUCUS

TRANSPORTS FOOD INTO THE STOMACH

DOES NOT PRODUCE DIGESTIVE ENZYMES

DOES NOT CARRY ON ABSORPTION

PERISTALSIS OCCURS FROM OESOPHAGUS TO ANUS

IT ALSO OCCURS IN URETERS,BILEDUCTS AND

UTERINE TUBES

CRICOPHARYNGEAL SPHINCTER: Upper sphincter of oesophagus, prevents air entering into oesophagus during respiration.

CARDIAC SPHINCTER : Lower sphincter of oesophagus, which prevents the reflux of acidic contents from stomach into oesophagus.

STOMACHOESOPHAGUS

STOMACH

SMALL

INTESTINE

LARGE

INTESTINE

LIVER

DILATED PORTION OF ALIMENTARY CANAL

25 CM IN LENGTH

STOMACH

FUNCTIONS

STORES FOOD

FORMS CHYME

GASTRIC EMPTYING

IN THE STOMACH ,DIGESTION OF

STARCH AND TRIGLYCERIDES CONTINUES,

DIGESTION OF PROTEINS BEGINS

SECRETES GASTRIC JUICE,WHICH CONTAINS HCL ( KILLS BACTERIA

AND DENATURES PROTEINS ), PEPSIN( BEGINS THE DIGESTION OF PROTEINS ),

INTRINSIC FACTOR ( AIDS ABSORPTION OF VITAMIN B12 )

AND GASTRIC LIPASE ( AIDS DIGESTION OF TRIGLYCERIDES )

SECRETES GASTRIN INTO BLOOD

NUTRIENTS ABSORBED IN STOMACH : WATER, IONS,SHORT CHAIN FATTY ACIDS,

DRUGS ( ASPIRIN ) AND ALCOHOL.

STOMACH - SHAPE

OESOPHAGUS

STOMACH - J SHAPED

DUODENUM

STOMACHPRESENTING PARTS

CARDIAC

ORIFICE

PYLORIC

ORIFICE

Gastrooesophageal

sphincter

Pyloric sphincter

SUB-DIVISIONS OF STOMACH

ANTRUM

INTERIOR OF STOMACH

GASTRIC FOLDS

(RUGAE)

GASTRIC CANAL

1. CARDIAC GLANDS - SECRETE MUCUS

2.FUNDIC AND BODY GLANDS -

a. ZYMOGENIC CELLS OR CHIEF CELLS OR PEPTIC CELLS –

SYNTHESIZE PEPSINOGEN GRANULES( INACTIVE)

( IN ROUGH ENDOPLASMIC RETICULULUM

STORED IN GOLGI APPARATUS)

INACTIVE PEPSINOGEN HCL ACTIVE PEPSIN

CHIEF CELLS ALSO SECRETE GASTRIC LIPASE

b. OXYNTIC CELLS OR PARIETAL CELLS SECRETE HCL WITH THE HELP

OF AN ENZYME CARBONIC ANHYDRASE

SECRETION IS REGULATED BY VAGUS AND

HORMONE GASTRIN

ALSO SECRETE INTRINSIC FACTOR OF CASTLE

WHICH HELPS ABSORPTION OF VIT B12 BY SMALL INTESTINE

c. MUCOUS NECK CELLS - secrete mucous

ENTEROENDOCRINE CELLS OR ARGENTAFFINS ( THEY TAKE UP SILVER STAIN )

( HORMONE SECRETING CELLS OF GIT )

PRESENT IN GASTRIC GLANDS ARE

G CELLS ( located in pyloric antrum ) - GASTRIN

ENTEROCHROMAFFIN CELLS - SEROTONIN

ENTEROCHROMAFFIN LIKE CELLS - HISTAMINE

DELTA CELLS ARE SOMATOSTATIN PRODUCING CELLS, FOUND IN STOMACH , INTESTINE

AND PANCREATIC ISLETS/ hypothalamus

MUCOUS NECK CELLS,CHIEF CELLS AND PARIETAL CELLS OF GASTRIC GLANDS ARE

EXOCRINE GLAND CELLS

THEIR SECRETIONS FORM GASTRIC JUICE , WHICH TOTALS 2000 – 3000 ML / DAY.

3.PYLORIC GLANDS

Contains mucus- secreting cells

G CELLS - GASTRIN ACTS LOCALLY ON GASTRIC GLANDS TO SECRETE HCL

PEPSIN

SALIVARY AMYLASE IS INACTIVATED BY ACIDIC GASTRIC JUICE , BUT LINGUAL LIPASE PRODUCED

BY THE TONGUE IS ACTIVATED , WHICH STARTS TO DIGEST FATS ( TRIGLYCERIDES INTO

FATTY ACIDS AND DIGLYCERIDES )

HCL SECRETION BY PARIETAL CELLS CAN BE STIMULATED BY SEVERAL SOURCES:

ACETYLCHOLINE ( Ach ) ( released by parasympathetic neurons)

GASTRIN ( secreted by Gcells )

HISTAMINE ( which is a paracrine substance released by mast cells )

histamine enhances the effects of acetylcholine and gastrin.

SMALL INTESTINE

LARGE

INTESTINESMALL

INTESTINE

EXTENSION

PYLORIC END OF

STOMACH

ILEO-CAECAL

JUNCTION

STOMACH

LARGE

INTESTINE

SMALL

INTESTINE

CAECUM

APPENDIX

SMALL INTESTINEPARTS - 3

2.JEJUNUM

3.ILEUM

1.DUODENUM

Gall

bladder

DUODENUMDO-dekadactulos -LENGTH IS EQUAL TO BREADTH

OF TWELVE FINGERS

25cm

DUODENUM

DUODENUMPROXIMAL DILATED AND FIXED PART OF SMALL INTESTINE

DEVOID OF MESENTRY

‘C’ SHAPED

JEJUNUM

MESENTRY

ILEUM

PANCREAS

DUODENUMPARTS

L1

L2

L3

1ST5cm

2ND10cm

3RD10cm

4TH2.5cm

PANCREAS

INTERIOR OF DUODENUM

1ST PART OF

DUODENUM

(DUODENAL

CAP)

HEAD OF

PANCREAS

SUPERIOR

MESENTERIC

VESSELS

CIRCULAR FOLDS

MINOR DUODENAL

PAPILLAE

MAJOR DUODENAL

PAPILLAE

BILE DUCT

PANCREATIC DUCT

DUODENUM

VILLI ARE BROAD, TALL, NUMEROUS

FEW GOBLET CELLS

BRUNNERS GLAND IN SUBMUCOSA

Note:Brunner’s gland secrete a fluid , rich in bicarbonate ionsand an enzyme (enterokinase) which helps activation of trypsinogenfrom the pancreas.

LIVER AND GALL BLADDER

LIVER

LARGEST GLAND OF BODY

EXOCRINE ENDOCRINE

VISCERAL PERITONEUM

LIVERThe outer surface of liver is lined by serous coat derived from visceral

peritoneum

Beneath the serous coat a thin layer of connective tissue known as glisson’s capsule encloses the entire organ and extends into its interior as numerous septa.

Radicles of portal vein, hepatic artery and bile ductules run together within these septa ensheathed by the glisson’s capsule in the form of portal triad.

Hepatic veins and other tributaries pass independently in the connective tissue septa

And are surrounded by laminae of hepatic cells

LIVERLiver is composed of parenchyma cells ( hepatocytes ) , connective tissue

stroma, sinusoids, bile canaliculi, numerous portal triads and tributaries of

hepatic veins.

Hepatic lobules are the structural and functional units of liver containing

hepatic cells arranged in the form of cords.

LIVERWEDGE SHAPED STRUCTURE

SITUATED IN RIGHT HYPOCHONDRIUM

EPIGASTRIUM

LEFT HYPOCHONDRIUM

FUNCTIONS OF LIVER

RELEASES PLASMA PROTEINS

LIBERATES UREA

CONVERTS BILIRUBIN INTO BILIVERDIN

FOR SECRETION INTO BILE

INACTIVATES TOXINS

STORES CARBOHYDRATES AS GLYCOGEN

TRIGLYCERIDES AS LIPIDS

WHEN REQUIRED RELEASES GLUCOSE AND

LIPIDS INTO BLOOD

LIVER

WEIGHT; MALE - 1.4 KG TO 1.8 KG

FEMALE - 1.2 KG TO 1.4 KG

HISTOLOGY OF LIVERStructural and functional unit of liver is

hepatic lobule

It is hexagonal ,central vein in centre ,portal triads

At angles

Portal triads contain branch of portal vein

Hepatic artery

Bile duct

Plates of hepatocytes radiate from central vein

Separated by hepatic sinusoids

COMPRISES OF:

• INTRAHEPATIC PART: BILE CANALICULI

BILE DUCTULES

INTERLOBULAR BILE DUCTS

• EXTRAHEPATIC PART: HEPATIC DUCTS

COMMON HEPATIC DUCT

GALL BLADDER

CYSTIC DUCT

COMMON BILE DUCT

BILIARY APPARATUS

SPHINCTER OF BOYDEN

SPHINCTER PANCREATICUS

SPHINCTER OF ODDI

SPHINCTERS OF EXTRA

HEPATIC BILIARY APPARATUS

GALL BLADDER

PEAR SHAPED RESERVOIR OF BILE

MEASUREMENTSLENGTH: 7 TO 10 CMSBREADTH: 3CMSCAPACITY: 30 TO 50ML

PARTSFUNDUSBODYNECK

GALL BLADDER -HISTOLOGYHAS 3 LAYERS;

MUCOSA

FIBROMUSCULAR LAYER

SEROSA

MUCOUS MEMBRANE LINED BY TALL SIMPLE

COLUMNAR EPITHELIUM

FIBROMUSCULAR LAYER COMPOSED OF FIBROUS

TISSUE MIXED WITH SMOOTH MUSCLE

NO SUBMUCOSA

DIFFERENCES BETWEEN JEJUNUM AND ILEUM

JEJUNUM

8 feet long

4 cm wide

INTERNAL FEATURES:

Circular folds are larger

and thickly set

Villi are longer and more numerous

Peyer’s patches are less numerous

The epithelial cells covering peyer’s patches

are known as M- Cells which help transport

of antigens to the underlying lymphoid cells

Of lamina propria through the discontinous

basement membrane beneath the M – cells.

ILEUM

12 feet long

3.5 cm wide

INTERNAL FEATURES;

Circular folds are smaller

And widely separated

Villi are shorter and less

Numerous

Peyer’s patches are more

Numerous, the patches are

Formed by the collection

Of lymphocytes and plasma cells,

Situated along the antimesenteric

Border. They may be affected in

Typhoid fever producing ulcers.

JEJUNUM

ILEUM

PEYER’S PATCHES

LARGE INTESTINE

SMALL INTESTINE

• 6.5 metres in length

• Presence of villi. Villi are longer and more

numerous in duodenum and jejunum

• The crypts of lieberkuhn ( intestinal glands )

are lined by absorptive cells ( columnar ) ,

goblet cells and paneth cells.

• Peyer’s patches are numerous in the ileum

• Circular folds ( plicae circulares,

valves of kerkring ) are present in

the entire small gut

LARGE INTESTINE

• 1.5 metres in length

• Absence of villi

• Crypts of lieberkuhn contain

Goblet cells. Paneth cells are

absent

• Few lymphoid follicles are

present

• Presence of 3 cardinal features:

• TAENIAE COLI

• SACCULATIONS

• APPENDICES EPIPLOICAE

CHARACTERISTIC FEATURES OF

LARGE INTESTINE

A FEW SUBSTANCES IN FOOD CAN BE ABSORBED

WITHOUT UNDERGOING DIGESTION: VITAMINS, IONS,CHOLESTEROL AND WATER.

MALT ( MUCOSA ASSOCIATED LYMPHATIC TISSUE - IN LAMINA PROPRIA ) CONTAIN IMMUNE SYSTEM CELLS

ALL ALONG THE GIT.

MUSCLES OF MOUTH , PHARYNX, TILL MIDDLE PART OF OESOPHAGUS, EXTERNAL ANAL SPHINCTER - MADE OF SKELETAL MUSCLE.

REST OF GIT IS MADE OF SMOOTH MUSCLE INNER SHEET OF CIRCULAR MUSCLE

OUTER SHEET OF LONGITUDINAL MUSCLE

SEROUS MEMBRANES ARE PERITONEUM, PLEURA AND PERICARDIUM - CONSISTS OF LAYER OF SIMPLE SQUAMOUS EPITHELIUM ( MESOTHELIUM ) WITH UNDERLYING SUPPORTIVE AREOLAR CONNECTIVE TISSUE

ZYGOMATIC GLAND ( infra orbital glands ) – FOUTH TYPE OF MAJOR SALIVARY GLAND - FOUND IN DOGS AND CATS , NOT PRESENT IN HUMANS AND RABBIT.

THANK YOU