DIGESTIVE SYSTEM part 1

Oral cavity, esophagus & stomach

Department of histology, cytology and embryology KhNMU

LECTURE

General description andGeneral description and significancesignificance

The digestive tract is: The digestive tract is: a long a long tubetube extending from extending from oral cavityoral cavity to the to the anusanus and and associated glandsassociated glands..

Main functions are: Main functions are: ingestion, fragmentation, ingestion, fragmentation, digestion, absorption of nutrientsdigestion, absorption of nutrients and and elimination of elimination of waste products.waste products.

Classification and embryogenesisClassification and embryogenesis

3 compartments:3 compartments: AnteriorAnterior Oral cavity, pharynx, Oral cavity, pharynx, esophagus esophagus

MiddleMiddle Gastrointestinal tract Gastrointestinal tract

PosteriorPosterior Last 1/3 rectum, anus Last 1/3 rectum, anus

EmbryogenesisEmbryogenesis

EmbryogenesisGut – from endoderm,

stomatodaeum, proctodaeum – from ectodermConnective tissue, muscles are from mesoderm

amnion

yolk sac

EmbryogenesisEmbryogenesis

Yolk Sac

Oral Plate

CloacalPlate

foregut

midgut

hindgut

Allantois

Heart

General plan of General plan of structurestructure FOUR principal membranes:FOUR principal membranes:

Mucosa: EpitheliumMucosa: Epithelium

Lamina propriaLamina propria

Muscularis mucosaeMuscularis mucosae SubmucosaSubmucosa Muscularis externaMuscularis externa Serosa or adventitiaSerosa or adventitia

1c

2

4

3a

2a

2b

3b

1a

1b

Mucosa: 1.epithelium (buccal)

Mucosa: 2. lamina propria – con.t. –nutrition, support, protection (GALT),

absorption, secrition (glands),

villi3. muscularis mucosae

Submucosa - Submucosa - con.t. - big bl.vessels, glands, nerve plexuses, lymphatic nodules,

provides motility of mucosa

Muscularis externa – circular, longitudinal layers

Serosa or adventitiaSerosa or adventitia

Oral Cavity Oral Cavity consists of a number of suborgansconsists of a number of suborgans

FunctionsFunctions::

Ingestion, Ingestion, STRUCTURESTRUCTURE::

Fragmentation Fragmentation 1. Mucosa1. Mucosa

Moistening Moistening 2. Submucosa2. Submucosa

Speech Speech (not always present ! )(not always present ! )

Facial expression Facial expression 3. Muscularis ext.3. Muscularis ext.

Sensory reception Sensory reception (facial muscles)(facial muscles)

Breathing Breathing 4. Adventitia4. Adventitia

(absent)(absent)

The The outer surfaceouter surface (skin) (skin) of the lip is covered by thin skin (ts). of the lip is covered by thin skin (ts).

The The inner inner surface (oral)surface (oral) is lined by a is lined by a mucosamucosa

The tThe transitional zoneransitional zone

oral side skin side

low mag.

oralskin

sk sk

sk

tsts

ss

ss

bv

sg

lpLipLip

LipLip

Vermilion - Vermilion - “red” transitional “red” transitional zonezone In newborn there are small villi for sucking In newborn there are small villi for sucking (Krok). (Krok).

The cheek is similar to the lipThe cheek is similar to the lip. .

red area

ss

p

bv

Tongue Tongue

EEpithelium (E) & underlying ct.pithelium (E) & underlying ct.

SSkeletal muscle (SM) runkeletal muscle (SM) runss in 3 planes. Embedded in the skeletal in 3 planes. Embedded in the skeletal muscle muscle lielie glands (G). glands (G).

PPapillae. Most numerous are conical, apillae. Most numerous are conical, keratinizedkeratinized filiformfiliform (f) (f) papillae; papillae; function – function – general sensationgeneral sensation

fungiformfungiform and and foliatefoliate papillae are scattered. papillae are scattered.

At the sulcus terminalis, lie 8 -12 large At the sulcus terminalis, lie 8 -12 large circumvallatecircumvallate papillae (C). papillae (C).

- - Taste sensationTaste sensation

E

SMG

Cf

Tongue, filiform & fungiform papillaeTongue, filiform & fungiform papillae

filifili

ctct

ss ss funginss

CCircumvallatircumvallate papillae papilla

TongueTongue

papilla with taste budspapilla with taste buds

high

med

fp

tb

TThe mucosa (m) is tightly bound to the bone (b)he mucosa (m) is tightly bound to the bone (b).. The The epithelium (ss) epithelium (ss) is disturbedis disturbed in chewing and swallowing in chewing and swallowing and so and so tends to be tends to be keratinizedkeratinized, and lamina propria , and lamina propria forms deep papillae, protruding in the epithelium.forms deep papillae, protruding in the epithelium.

Hard Hard PalatePalate

Maxillaunerupted tooth

hard palate

epithelium

m

b

ss

lowmed

Soft Soft palatepalate

smEpithelium

sg

oral cavity

Its upper surface faces the respiratory passages Its upper surface faces the respiratory passages - - pseudostratified epitheliumpseudostratified epithelium..

Facing oral cavity epithelium isFacing oral cavity epithelium is stratified squamous stratified squamous. . Krok !Krok !

Lingual Lingual TonsilTonsil

Lingual tonsil (T) Lingual tonsil (T) locateslocates on the dorsum of the tongue. on the dorsum of the tongue.

Together with palatine, pharyngeal tonsils form Together with palatine, pharyngeal tonsils form "ring"."ring".

At time of chronic inflammation may undergo At time of chronic inflammation may undergo tonsilectomy.tonsilectomy.

ssc

mg

sk

T

TOOTHTOOTH

ToothToothdevelopmendevelopmentt Enamel organ Enamel organ

(epith)(epith) AmeloblastsAmeloblasts EnamelEnamel Dental papillaDental papilla OdontoblastsOdontoblasts DentineDentine Dental sac –Dental sac –

cementum,cementum,

pulppulp

SALIVARY GLANDSSALIVARY GLANDS

SalivaSaliva: water, mucus, amylase, : water, mucus, amylase, lysozyme, a/b, ions lysozyme, a/b, ions

I. Large salivary glandsI. Large salivary glands

3 pairs: parotid, submandibular, sublingual 3 pairs: parotid, submandibular, sublingual

function - function - IN RESPONIN RESPONcece TO TOPARASYMPATHETIC ACTIVITYPARASYMPATHETIC ACTIVITY

II. Minor salivary glandsII. Minor salivary glandsffunction - CONTINUOUSLYunction - CONTINUOUSLY

General structureGeneral structure Compound branched acinar or acino-tubular Compound branched acinar or acino-tubular

glandsglands Connective tissue capsuleConnective tissue capsule Lobulated structureLobulated structure Lobules contain secretory units and small Lobules contain secretory units and small

ductsducts

Interlobular connective tissue with ducts and Interlobular connective tissue with ducts and vesselsvessels

5 Intercalated duct

Striated duct,

Next are interlobular and general

Mucous acinus

Serous acinus

Secretory unitSecretory unit

Myoepithelial cells (contractile)

surround secretory portions

and small ducts – intercalated and striated

Myoepithelial cells

Nucleus

ParotidParotid

high

lowlow

su

nRER

sd

The parotid is a serous The parotid is a serous gland secreting amylase. gland secreting amylase.

Secretory unit Secretory unit (s(suu)) is is acinaracinar. .

Pyramidal aPyramidal acinar cells have cinar cells have round basally-placed round basally-placed nuclei (n) with abundant nuclei (n) with abundant basal RERbasal RER

low

med

Sublingual Sublingual glandgland

This gland has This gland has mucous &mucous & mixed mixed secretory secretory unitunits but s but

mostly mucous.mostly mucous.high

me

med

id

itd

n

idsd

MixedMixed acinus with a acinus with a SSerous erous demilunedemilune

msu

msu

Submandibular glandSubmandibular gland

It is It is predominantly serous gland shows blue, predominantly serous gland shows blue, pure serous acini (sa) & pale, mucous pure serous acini (sa) & pale, mucous and and mixed with mixed with serous demilunes (m/s) serous demilunes (m/s)..

low

highmed

lobule

ided

sa

m/s

sublingual gland

Submandibular gland

Striated duct

demilune

Demilune

Intercalated duct

Parotid gland

Sublingual Sublingual glandgland

CompaCompare!re!

Demilune

Striated duct

Esophagus Esophagus (=(= PharynxPharynx))

6-7 longitudinal folds.6-7 longitudinal folds.

The muscularis externa. The muscularis externa.

The upper The upper 1/3rd1/3rd is composed of skeletal muscle; is composed of skeletal muscle; the lower the lower 1/3rd1/3rd - - smooth muscle; the middle smooth muscle; the middle 1/3rd1/3rd shows a blending of the two varieties of shows a blending of the two varieties of muscle.muscle.

Epithelium is stratified squamous nonkeratinizedEpithelium is stratified squamous nonkeratinized

Esophagus

1) Mucosa-epithelium, laminapropria & muscularis mucosae,2) Submucosa, 3) Muscularis externa 4) Adventitia

EsophagusEsophagus

Mucosal Mucosal cardiac cardiac glands (mg) are in the lamina propria (lp) glands (mg) are in the lamina propria (lp) (mm) in the upper and lower thirds of the esophagus(mm) in the upper and lower thirds of the esophagus. .

If they are not fully effective, the excessive reflux results in If they are not fully effective, the excessive reflux results in pyrosis (heartburn) – the rise of the gastric contents upward pyrosis (heartburn) – the rise of the gastric contents upward toward the neck.toward the neck.

mg

lp

ss

mm sm

me

EsophagusEsophagus

A mucous A mucous esophageal esophageal glandglands propers proper (mg) (mg)

lie in the submucosa (s). lie in the submucosa (s).

mgs

mm

me

muscularis externa (me). muscularis externa (me). = = smoothsmooth (sm) & skeletal (sm) & skeletal muscle (sk). muscle (sk).

lymphatic nodules (lymphatic nodules (LL)) are in the mucosa (m). are in the mucosa (m).

L

sub

me

sm

sk

mEsophagus,

middle 1/3rd - med. mag. .

EsophagusEsophagus

The enteric nervous system is extensive and its The enteric nervous system is extensive and its neurons neurons and fibers and fibers form form in thein the submucosa submucosa ((Meissner’s plexusMeissner’s plexus) () (M')M') and in the muscularis and in the muscularis externa (externa (Auerbach’s plexusAuerbach’s plexus) () (A'A').).

M'

A'str.sq.epi

musc. muc.submuc.muscul.

externa.

submucosal gl.

lymphatic nodule

lumen

med

high

high

Esophagus/Stomach junction. -

Epithelium is changed from stratified squamous to

simple columnar (sc).

1

2

3

E

E

S

S

sc

sc

gp

gp

low

med high

Stomach - generalStomach - general

The process of The process of digestiondigestion essentially begins in the stomach; essentially begins in the stomach; little little absorptionabsorption and and excretionexcretion also also occur here.occur here.

The stomach is composed of a mucosa, submucosa, The stomach is composed of a mucosa, submucosa, muscularis externa & serosa. muscularis externa & serosa.

The mucosal lining is a The mucosal lining is a simple columnar simple columnar secretsecretoryory epithelium epithelium (mucous)(mucous). .

Folds (rugae),Folds (rugae), gastric pits gastric pits, mammilated areas., mammilated areas.

GlandsGlands vary in different regions of the stomach. vary in different regions of the stomach.

StomachStomach mucosa:mucosa:

``````epitheliumepithelium

lamina propria:lamina propria: gastricgastric glands ; ;

muscularis mucosae: both muscularis mucosae: both circular and circular and longitudinal longitudinal layerslayers of SM.of SM.

submucosa:submucosa:

muscularis:muscularis: the inner oblique layer, the inner oblique layer, circular layer and longitudinal layer of circular layer and longitudinal layer of SM. SM.

serosa serosa

Stomach, mucosal lining & gastric pitsStomach, mucosal lining & gastric pitsGGastric pits (gp)astric pits (gp) are are invaginations ofinvaginations of a simple columnar a simple columnar

epitheliumepithelium

The mucus blanket which protects the lining from The mucus blanket which protects the lining from stomach acids is present here.stomach acids is present here.

gpsc

Lamina propria contains glandsLamina propria contains glands fundic glandsfundic glands (in the body, fundus) secrete the (in the body, fundus) secrete the

enzymes and acid of the stomach. While enzymes and acid of the stomach. While cardiaccardiac and and pyloricpyloric glands predominantly secrete mucus. glands predominantly secrete mucus.

The fundic glands are simple tubular.The fundic glands are simple tubular.

They contain 4 cell types:They contain 4 cell types:

1. Mucous neck cells1. Mucous neck cells2. Chief cells 2. Chief cells , , or zymogenic cells or zymogenic cells

columnar and basophilic cells - in the columnar and basophilic cells - in the body of the glands. body of the glands.

produce produce pepsinogen and lipasepepsinogen and lipase..

3. 3. Parietal cells

secrete secrete hydrochloric acidhydrochloric acid ( HCL ) and ( HCL ) and intrinsic factorintrinsic factor. . The latter is necessary for The latter is necessary for

absorption of vitamin Babsorption of vitamin B1212 in the ileum in the ileum

4. Enteroendocrine cells (APUD)4. Enteroendocrine cells (APUD)

20 different types20 different types 4 principal hormones:4 principal hormones: Gastrin Hcl secretionGastrin Hcl secretion Secretin, cholecystokinin (CCK), Secretin, cholecystokinin (CCK),

gastric inhibitory peptide (GIP) gastric inhibitory peptide (GIP) pancreatic and gallblader pancreatic and gallblader activity and gastric secretion activity and gastric secretion

Pernicious anemiaPernicious anemia follows the follows the absence of parietal cells (i.e. loss of absence of parietal cells (i.e. loss of epithelium due to gastric ulcer)epithelium due to gastric ulcer)

Disturbance of different cells may call Disturbance of different cells may call the different pathology.the different pathology.

Digestion of different substances Digestion of different substances begins in different regions.begins in different regions.

Fundic Fundic stomachstomach

The lowest mag. shows the mucosaThe lowest mag. shows the mucosa (m)(m), , submucosasubmucosa (sm) with (sm) with folds called rugaefolds called rugae (r) (r)

& the muscularis externa (me). At higher mag. gastric pits (gp)& the muscularis externa (me). At higher mag. gastric pits (gp), , fundic glands (fg), &fundic glands (fg), & muscularis mucosa (mm) comprisemuscularis mucosa (mm) comprisess the the mucosa. Outside is the submucosa (sm) and muscularis mucosa. Outside is the submucosa (sm) and muscularis externa (me). externa (me).

2

m sm

r

me

gp

fg

mmsm

me

low

med

Fundic Fundic stomachstomachmucosamucosa

In fundic stomach,In fundic stomach,

gastric pits occupy gastric pits occupy about 1/about 1/5 5 the the mucosa; fundic mucosa; fundic glands comprise the glands comprise the remaining 3/4ths. remaining 3/4ths.

gastricpit

fundicgland

Isthmus

Neck

Base

Cardiac StomachCardiac Stomach, ,

GGastric pitsastric pits occupy ½ of occupy ½ of mucosamucosa. .

GGastric glands astric glands are simple tubular are simple tubular and slightly branchedand slightly branched

Cells are mucus-secreting andCells are mucus-secreting and

occational endocrineoccational endocrine

gastricpit

cardiacglands

sc

mm

Stomach, pyloricStomach, pyloric

GGastric pitsastric pits occupy 3/4ths the depth of the occupy 3/4ths the depth of the mucosa; the remaining 1/4th mucosa; the remaining 1/4th areare pyloric gland pyloric glands s – short and branched– short and branched. .

The major cell of the gland is the pale mucous The major cell of the gland is the pale mucous (mn); (mn); parietal cells are absentparietal cells are absent as the pyloric as the pyloric stomach nears the intestine.stomach nears the intestine.

gastricpit

gastric gland

mn low

Fundic Stomach, nerve supplyFundic Stomach, nerve supply, , - med & high mag - med & high mag

Elements of the submucosal (s) and myenteric (m) nerve plexuses are Elements of the submucosal (s) and myenteric (m) nerve plexuses are present.present.

fundicglands

musc.mucosa

submucosa muscularisexterna

inner

middle

outer

s

m

smooth muscle

artery

vein