lipslips Each lip is divided into:Each lip is divided into:

1.1. External aspect----thin Skin with sweat External aspect----thin Skin with sweat glands, hair follicles and sebaceous glands.glands, hair follicles and sebaceous glands.

2.2. Vermilion region---pink, very thin skin Vermilion region---pink, very thin skin devoid of glands and hair follicles.devoid of glands and hair follicles.

3.3. Mucous or internal aspect-----str.sq. Mucous or internal aspect-----str.sq. epith.non-kerat. With subepith.irregular epith.non-kerat. With subepith.irregular collagenous C.T having minor mucous collagenous C.T having minor mucous salivary glands.salivary glands.

* The core of the lips is composed of skeletal * The core of the lips is composed of skeletal muscle fibersmuscle fibers

LipLip

Oral cavity.Oral cavity.

Oral mucosa:Oral mucosa:*Gingiva, dorsal surface of the anterior two thirds *Gingiva, dorsal surface of the anterior two thirds

of the tongue, and hard palate are covered by of the tongue, and hard palate are covered by keratinized or partially (parakeratinized) keratinized or partially (parakeratinized) str.sq.epith. with underlying dense irregular str.sq.epith. with underlying dense irregular collagenous C.T.collagenous C.T.

*The reminder of oral cavity is covered by non-*The reminder of oral cavity is covered by non-keratinized str. Sq. epith. With underlying looser keratinized str. Sq. epith. With underlying looser collagenous C.T.collagenous C.T.

TeethTeeth Each tooth is suspended in bony socket, the Each tooth is suspended in bony socket, the

alveolus by the periodontal (dense irregular alveolus by the periodontal (dense irregular collagenous C.T.)collagenous C.T.)

Each tooth is formed of:Each tooth is formed of:

1-Crown—visible part.1-Crown—visible part.

2-Root----in the alveolus.2-Root----in the alveolus.

3-Cervix---inbetween. 3-Cervix---inbetween.

*The inner part of tooth is the pulp that contain *The inner part of tooth is the pulp that contain soft vascular C.T contains bl. and lymph soft vascular C.T contains bl. and lymph Vessels and nervesVessels and nerves

Mineralized componentsMineralized components

They are :They are : a.Dentina.Dentin----surrounds the pulp and is covered ----surrounds the pulp and is covered

with;with; b.Enamelb.Enamel –that cover the crown.–that cover the crown. c.Cementumc.Cementum----that cover the root.----that cover the root.

TeethTeeth

PalatePalate

It is composed of:It is composed of: Hard palate (keratinized-st. sq.epith.)Hard palate (keratinized-st. sq.epith.) Soft palate (non-ker.st.sq.epit.)Soft palate (non-ker.st.sq.epit.) Uvula (non-ker.st.sq.epith)Uvula (non-ker.st.sq.epith)

They separate the nasal cavity from the They separate the nasal cavity from the oral one.oral one.

TongueTongue It hasIt has::

1-Dorsal surface---its ant. two thirds is covered 1-Dorsal surface---its ant. two thirds is covered with ker. St. sq.epith. and separated from post with ker. St. sq.epith. and separated from post one third (covered with non-ker. St. sq.epith) by one third (covered with non-ker. St. sq.epith) by a shallow, V-shaped groove, the a shallow, V-shaped groove, the sulcus sulcus terminalis.terminalis.

2-Ventral surface---non-ker. St.sq.epith.2-Ventral surface---non-ker. St.sq.epith.

3-Core of skeletal muscle fibers.3-Core of skeletal muscle fibers.

*The dorsal surface of posterior one third has *The dorsal surface of posterior one third has lingual tonsils.lingual tonsils.

TongueTongue

Lingual tonsilLingual tonsil

Lingual papillaeLingual papillaeThey are located on the dorsal & lateral aspect of They are located on the dorsal & lateral aspect of

the tongue.the tongue.

There are four types:There are four types:

1.Filiform papilla1.Filiform papilla : slender structure, covered by : slender structure, covered by ker.st. sq. epith.DO NOT have taste buds.ker.st. sq. epith.DO NOT have taste buds.

2.Fugiform papilla-2.Fugiform papilla---as mushroom has slender --as mushroom has slender stalk connects a broad cap to tongue surface.It stalk connects a broad cap to tongue surface.It is covered by non-ker. Str. Epith.It has taste is covered by non-ker. Str. Epith.It has taste buds on dorsal surface of the cap.buds on dorsal surface of the cap.

Filliform &Fungi form papillaeFilliform &Fungi form papillae

3.Foliate papillae:3.Foliate papillae: are located along are located along the posterior aspect of the tongue. the posterior aspect of the tongue. They have taste buds in neonate only. They have taste buds in neonate only. They have furrows in which glands of They have furrows in which glands of Von Ebner (serous) open.Von Ebner (serous) open.

4.Circumvallate papillae-4.Circumvallate papillae---8 to 12 just --8 to 12 just ant. To sulcus terminalis. They have ant. To sulcus terminalis. They have Von Ebner serous glands. They have Von Ebner serous glands. They have taste buds on their sides only.taste buds on their sides only.

Circumvallate papillaCircumvallate papilla

Taste budsTaste buds

Are intra-epithelial sensory organs for Are intra-epithelial sensory organs for perception of taste.perception of taste.

Each taste bud is formed of:Each taste bud is formed of:

1.Dark cells (type I)1.Dark cells (type I)

2.Light cells (type II)2.Light cells (type II)

3.Intermediat cells (type III)3.Intermediat cells (type III)

4.Basal cells (type IV)4.Basal cells (type IV)

*Nerve fibers synapse with types I, II, and III (they *Nerve fibers synapse with types I, II, and III (they have long microvilli protruding from taste pores)have long microvilli protruding from taste pores)

Taste budsTaste buds

Salivary glandsSalivary glands

There two types of salivary glands:There two types of salivary glands:

Minor salivary glandsMinor salivary glands (scattered in (scattered in the mucosa of oral cavity-mucous the mucosa of oral cavity-mucous secreting).secreting).

Major salivary glandsMajor salivary glands ( Parotid, sub ( Parotid, sub mandibular and sub lingual)mandibular and sub lingual)

Major salivary glandsMajor salivary glandsThere are three pairs of major salivary There are three pairs of major salivary

glands, Parotid, submandibular, and glands, Parotid, submandibular, and sublingual.sublingual.

They have C.T capsule. provides They have C.T capsule. provides septa that divide the glands into lobes septa that divide the glands into lobes and lobules and lobules (Stroma).(Stroma).

Their Their parenchymaparenchyma consists of consists of secretory portion (tubuloalveolar secretory portion (tubuloalveolar glands) and ducts portion.glands) and ducts portion.

Secretory portionsSecretory portions Are formed of Are formed of serousserous and/or and/or mucousmucous serous serous

secretory cells arranged as acini (alveoli-secretory cells arranged as acini (alveoli-serous) or tubules (mucous) that are couched serous) or tubules (mucous) that are couched by by myoepithelial cellsmyoepithelial cells..

Myoepithelial (basket )cells.Myoepithelial (basket )cells.They share the basal lamina of acinar cells They share the basal lamina of acinar cells

(hemidesmosomes).(hemidesmosomes).They envelope the cells of secretory acinus and They envelope the cells of secretory acinus and

intercalated ducts (desmosomes)intercalated ducts (desmosomes)They have several long processes.They have several long processes.They are rich in actin and myosin.They are rich in actin and myosin.They press on the acinus to release the product.They press on the acinus to release the product.

Salivary Salivary secretory secretory unitunit

Serous cellsSerous cells Secrete proteins and polysaccharides.Secrete proteins and polysaccharides. Are pyramidal with single round, basally Are pyramidal with single round, basally

located nuclei.located nuclei. Are rich in rER, Golgi complex, basal Are rich in rER, Golgi complex, basal

mitochondria, and epically situated mitochondria, and epically situated secretory granules.secretory granules.

They have tight junctions, intercellular They have tight junctions, intercellular canaliculi and interdigitated baso-lateral canaliculi and interdigitated baso-lateral processes.processes.

Mucous cellsMucous cells

Are short pyramidal cells with basal Are short pyramidal cells with basal flattened nuclei.flattened nuclei.

Have few mitochondria, rER, but rich in Have few mitochondria, rER, but rich in Golgi complex (to form carbohydrates).Golgi complex (to form carbohydrates).

Have less lateral processes and Have less lateral processes and intercellular canaliculi than serous cells.intercellular canaliculi than serous cells.

Apices of cells are rich in secretory Apices of cells are rich in secretory granules.granules.

Duct portionsDuct portions Are highly branched ducts.Are highly branched ducts. Begin with the smallest intercalated ducts that Begin with the smallest intercalated ducts that

formed of small cuboidal cells having formed of small cuboidal cells having myoepithelial cells.myoepithelial cells.

Intercalated ducts merge to form striated ducts Intercalated ducts merge to form striated ducts which are cuboidal to columnar cells with which are cuboidal to columnar cells with basolateral folds containing mitochondria. They basolateral folds containing mitochondria. They join together to form intralobular ducts that unit join together to form intralobular ducts that unit to form interlobular ducts that join to form to form interlobular ducts that join to form intralobar and interlobar ducts.intralobar and interlobar ducts.

Terminal ducts open into the oral cavity.Terminal ducts open into the oral cavity.

Parotid GlandParotid Gland

The largest salivary gland but The largest salivary gland but produce 30% of salivary output.produce 30% of salivary output.

It secrets It secrets pure serouspure serous secretion secretion that rich in amylase enzyme, that rich in amylase enzyme, lactoferrins, lysozymes and lactoferrins, lysozymes and secretory IgAsecretory IgA

Parotid glandParotid gland

Submandibular GlandSubmandibular Gland It produces 60% of salivary It produces 60% of salivary

output.output. It is mixed but the major portion It is mixed but the major portion

(90%) is serous and 10% is (90%) is serous and 10% is mucous.mucous.

It has few serous demilunes that It has few serous demilunes that capped the mucous tubular capped the mucous tubular secretory unit.secretory unit.

Submandibular glandSubmandibular gland

Sublingual GlandSublingual Gland It is very small and responsible for 5% It is very small and responsible for 5%

of salivary secretion.of salivary secretion. It is composed of mucous tubules It is composed of mucous tubules

with serous demilunes.with serous demilunes. It produces mixed , but mostly It produces mixed , but mostly

mucous saliva.mucous saliva. Its duct system does not form Its duct system does not form

terminal duct, instead several ducts terminal duct, instead several ducts open into the floor of oral cavity.open into the floor of oral cavity.

Sub lingual Sub lingual glandgland

Alimentary CanalAlimentary Canal Is the tubular portion of digestive Is the tubular portion of digestive

system.system.About 9 meters and subdivided About 9 meters and subdivided

into: esophagus, stomach, small into: esophagus, stomach, small intestine (duodenum, jejunum and intestine (duodenum, jejunum and ileum), and large intestine ileum), and large intestine (cecum, colon, rectum, anal (cecum, colon, rectum, anal canal, and appendix)canal, and appendix)

General structure of Alimentary tractGeneral structure of Alimentary tract

It is formed of 4 concentric layers:It is formed of 4 concentric layers:

I.Mucosa II.Submucosa III.Muscularis externaI.Mucosa II.Submucosa III.Muscularis externa

IV.Serosa (adventitia) IV.Serosa (adventitia)

I-I- MUCOSAMUCOSA

It is formed of :It is formed of :

1-Epithelium.1-Epithelium.

2-Lamina propria2-Lamina propria (Vascular C.T) that contains (Vascular C.T) that contains lymph vessels, nodules and glands.lymph vessels, nodules and glands.

3-Muscularis mucosa:3-Muscularis mucosa: longitudinal smooth longitudinal smooth muscle.muscle.

The wall of GIT.The wall of GIT.(esophagus)(esophagus)

II-SUBMUCOSAII-SUBMUCOSA Is formed of dense irregular elastic Is formed of dense irregular elastic

C.T.C.T. It has glands It has glands ONLYONLY in in esophagusesophagus

and and duodenumduodenum.. It is rich in blood and lymph vessels.It is rich in blood and lymph vessels. It has enteric nervous plexus It has enteric nervous plexus

((Meissner”s plexusMeissner”s plexus) that houses ) that houses also post ganglionic parasympathetic also post ganglionic parasympathetic nerve cell bodiesnerve cell bodies..

III-MUSCULRIS EXTERNAIII-MUSCULRIS EXTERNA It is responsible for peristaltic activity.It is responsible for peristaltic activity. It is composed of smooth muscle (EXCEPT in It is composed of smooth muscle (EXCEPT in

esophagus, has both smooth & skeletal fibers).esophagus, has both smooth & skeletal fibers). They are arranged helically.They are arranged helically. Usually organized as inner circular and outer Usually organized as inner circular and outer

longitudinal.longitudinal. Between the two layers they have Auerbach’s Between the two layers they have Auerbach’s

myenteric plexus.myenteric plexus. that houses also post ganglionic that houses also post ganglionic

parasympathetic nerve cell bodiesparasympathetic nerve cell bodies

Musculsris externaMusculsris externa

Auerbach’s myenteric plexus

IV-SEROSA OR ADVENTITIAIV-SEROSA OR ADVENTITIA It covers the muscularis externa.It covers the muscularis externa. It is formed of thin layer of vascular It is formed of thin layer of vascular

C.T.C.T. If it is surrounded by simple If it is surrounded by simple

squamous epith.of the visceral layer squamous epith.of the visceral layer of peritoneum (mesothelium)---It is of peritoneum (mesothelium)---It is called called serosa.serosa.

If the organ is retropritoneal i.e NO If the organ is retropritoneal i.e NO epith.—It is called epith.—It is called adventitia.adventitia.

EsophagusEsophagus MucosaMucosa---stratified sq.epith non-ker,fibroelasic ---stratified sq.epith non-ker,fibroelasic

lamina propria and longitudinal muscularis lamina propria and longitudinal muscularis mucosa (smooth muscle).mucosa (smooth muscle).

L.P has cardiac glands (mucous) near the L.P has cardiac glands (mucous) near the pharynx (upper region) and stomach (lower pharynx (upper region) and stomach (lower region).region).

Submucosa–Submucosa– has mucous esophageal glands has mucous esophageal glands proper.proper.

Muscularis externa Muscularis externa of upper third is skeletal of upper third is skeletal muscle, middle third is both smooth&skeletal muscle, middle third is both smooth&skeletal and the lowest third is smooth muscle.and the lowest third is smooth muscle.

Adventitia Adventitia until pierces diaphragm---serosauntil pierces diaphragm---serosa

Mucosa and submucosa of Mucosa and submucosa of esophagusesophagus

submucosa

Gastro-oesophageal junctionGastro-oesophageal junction

stomachesophagus

Parts of the Parts of the stomachstomach

Fundic mucosaFundic mucosa

Fundic glands have:

Short pits—one forth of mucosa.

Simple or branched tubular glands.

Are rich in parietal & chief cells.

Fundic gland

Surface columnar gastric cellSurface columnar gastric cell

They secrete thick mucous

Mucus neck cellMucus neck cell

Parietal cellParietal cell Acidophilic cells, apical invaginations that have canaliculi lined by microvilli.

Secrete HCl and gastric intrinsic factor (absorption of Vit.B12 in the ileum).

Chief cellChief cell*Basophilic cytoplasm.

*Secrete pepsinogen, rennin and gastric lipase

DNES cellsDNES cells

Pyloric glandsPyloric glands

Fundic glandsFundic glands Their pits are short about one quarter of length Their pits are short about one quarter of length

of mucosa.of mucosa. Are simple or branched tubular glands.Are simple or branched tubular glands. Are numerous and crowded.Are numerous and crowded.

Pyloric glandsPyloric glands * Their pits are deep---about half the length of * Their pits are deep---about half the length of

mucosa.mucosa. * They are branched and convoluted---many * They are branched and convoluted---many

cross sections.cross sections. * The predominant cells are mucous neck cells * The predominant cells are mucous neck cells

that secrete both mucous and lysozyme.that secrete both mucous and lysozyme.

Small intestineSmall intestine It has 3 regions: duodenum, jejunum and ileum.It has 3 regions: duodenum, jejunum and ileum. It has:It has:

* Plicae circulares---transverse folds of mucosa and * Plicae circulares---transverse folds of mucosa and submucosa.submucosa.

*Villi—Finger like protrusions of lamina propria that *Villi—Finger like protrusions of lamina propria that is covered with epithelium.They contain Bl. is covered with epithelium.They contain Bl. &lymphatic vessels (lacteal), smooth muscle &lymphatic vessels (lacteal), smooth muscle fibers, loose CT and lymphoid cells.fibers, loose CT and lymphoid cells.

* Micrvilli—modifications of the apical region of * Micrvilli—modifications of the apical region of plasmalemma of epithelial cells of villi and surface plasmalemma of epithelial cells of villi and surface epithelium.epithelium.

Crypts of Lieberkuhn-invaginations of epithelium Crypts of Lieberkuhn-invaginations of epithelium into the L.P between the villi form glandsinto the L.P between the villi form glands

Cells of the villi and crypts of small Cells of the villi and crypts of small intestineintestine

Cells covering the Villi Surface absorptive cells that has brush Surface absorptive cells that has brush

(microvilli) border and covered wih thick (microvilli) border and covered wih thick glycocalx that has dipeptidase and glycocalx that has dipeptidase and disaccharidase enzymes.They have Junction disaccharidase enzymes.They have Junction complex.complex.

Goblet cells—Increase toward the ileum.Goblet cells—Increase toward the ileum. DNES cells.DNES cells. M cells (microfold cells)-phagocytose and M cells (microfold cells)-phagocytose and

transport Ag present in the intestinal lumen.transport Ag present in the intestinal lumen.

Absorbtive columnar cellsAbsorbtive columnar cells

M-cellM-cell

Crypts of Lieberkuhn They are simple tubular glands that open They are simple tubular glands that open

between villi.between villi. They are composed of surface absorptive cells, They are composed of surface absorptive cells,

goblet cells, regenerative cells, DNES cells and goblet cells, regenerative cells, DNES cells and Paneth cells.Paneth cells.

Paneth cells occupy the bottom of crypts.They Paneth cells occupy the bottom of crypts.They have acidophilic (eosinophilic) secretory have acidophilic (eosinophilic) secretory granules. They secrete lysozyme (antibacterial granules. They secrete lysozyme (antibacterial agent)agent)

Paneth cellPaneth cell

Submucosa of the duodenumSubmucosa of the duodenum Is formed of dense irregular fibroelasic Is formed of dense irregular fibroelasic

CT.CT. Rich in bl. &lymphatic vessles.Rich in bl. &lymphatic vessles. Contains Meissner’s plexus Contains Meissner’s plexus

(parasympathetic).(parasympathetic). Contains Brunner’s glands that producea Contains Brunner’s glands that producea

mucous and bicarbonate-rich fluid as well mucous and bicarbonate-rich fluid as well as urogastron that inhibits HCl production.as urogastron that inhibits HCl production.

DuodenumDuodenum

Wall of the Wall of the duodenumduodenum

DuodenumDuodenum

Gastrodeodenal junctionGastrodeodenal junction

Regional differences of small intestineRegional differences of small intestine Duodenum is the shortest part (25cm). Its Duodenum is the shortest part (25cm). Its

villi are broader, taller and more numerous. villi are broader, taller and more numerous. Its submucosa has Brunner’s glands.Its submucosa has Brunner’s glands.

Jejunum-its villi are narrower, shorter. And Jejunum-its villi are narrower, shorter. And sparser than in duodenum. Goblet cells are sparser than in duodenum. Goblet cells are more.more.

Ileum-its villi are shortest, sparest, and Ileum-its villi are shortest, sparest, and narrowest. Its lamina propria has lymphoid narrowest. Its lamina propria has lymphoid nodules (peyer’s patches) opposite the nodules (peyer’s patches) opposite the attachment of the mesentery.attachment of the mesentery.

Large intesineLarge intesine It is divided into-cecum, colon, rectum, and It is divided into-cecum, colon, rectum, and

anus –(appendix is blind outpouching of the anus –(appendix is blind outpouching of the cecum).cecum).

It has NO villi.It has NO villi. It is rich in crypts that are composed of same It is rich in crypts that are composed of same

cells as small intestine but NO Paneth cells.cells as small intestine but NO Paneth cells. Goblet cells increase from cecum to the Goblet cells increase from cecum to the

sigmoid.sigmoid. The outer layer of muscularis externa is not The outer layer of muscularis externa is not

continuous (3 fascicles-taeniae coli).continuous (3 fascicles-taeniae coli). Serosa has fat called appendices epiploicae.Serosa has fat called appendices epiploicae.

ColonColon

Vermiform Appendix Vermiform Appendix It is long diverticulum of cecum.It is long diverticulum of cecum. It has shallow crypts of Lieberkuhn.Its It has shallow crypts of Lieberkuhn.Its

mucosa is composed of surface mucosa is composed of surface absorptive cells, goblet cells, DNES absorptive cells, goblet cells, DNES cells, M-cells, infrequent Paneth cells cells, M-cells, infrequent Paneth cells and lymphoid nodules around the and lymphoid nodules around the wall.wall.

It is invested by serosa.It is invested by serosa.

Vermiform appendix (Human)Vermiform appendix (Human)

Vermiform appendix (Rabbit)Vermiform appendix (Rabbit)

Rectum and Anal canalRectum and Anal canal Rectum has fewer but deeper crypts than colon.Rectum has fewer but deeper crypts than colon. Epithelium of anal mucosa is simple cuboidal Epithelium of anal mucosa is simple cuboidal

from rectum to pectinate line, then st.sq.non-ker. from rectum to pectinate line, then st.sq.non-ker. Epith to the anus, then st.sq.ker. Epith. At anus.Epith to the anus, then st.sq.ker. Epith. At anus.

Lamina propria of anal canal has anal glands.Lamina propria of anal canal has anal glands. Submucosa of anal canal has internal and Submucosa of anal canal has internal and

external hemorroidal plexuses.external hemorroidal plexuses. It has internal and external anal sphincters.It has internal and external anal sphincters.

PancreasPancreas

It is both an exocrine (digestive juices) & It is both an exocrine (digestive juices) & an endocrine (hormones) gland.an endocrine (hormones) gland.

The excretory part is formed of acini & The excretory part is formed of acini & ducts.ducts.

Acinar cells are pyramidal cells with basal Acinar cells are pyramidal cells with basal round nuclei that surrounded by basophilic round nuclei that surrounded by basophilic cytoplasm (rER, polysomes).cytoplasm (rER, polysomes).

Apex of acinar cells have zymogen Apex of acinar cells have zymogen granules-acidophilic.granules-acidophilic.

Acinar cells secrete many digestive Acinar cells secrete many digestive enzymes in the duodenum.enzymes in the duodenum.

Duct portion of PancreasDuct portion of Pancreas Ducts begins within the center of acini with the Ducts begins within the center of acini with the

terminus of intercalated duct forming terminus of intercalated duct forming centroacinar cells (pale simple cuboidal cells) centroacinar cells (pale simple cuboidal cells) but not form wall of acini.but not form wall of acini.

Acini have not myoepithelial cells.Acini have not myoepithelial cells. Centroacinar cells &intercalated cells secrete a Centroacinar cells &intercalated cells secrete a

bicarbonate-rich buffer solution.bicarbonate-rich buffer solution. Intercalated ducts merge to form intralobular Intercalated ducts merge to form intralobular

ducts that merge to form interlobular ducts, that ducts that merge to form interlobular ducts, that give main pancreatic duct.give main pancreatic duct.

PancreasPancreas

PancreasPancreas

Endocrine portion (Islets of Endocrine portion (Islets of Langerhans)Langerhans)

Islet is pale, spherical vascularized collection of Islet is pale, spherical vascularized collection of cells.cells.

It is surrounded by reticular cells.It is surrounded by reticular cells. It is formed of 5 types of cells:It is formed of 5 types of cells: ββ cells—70% more in center—secrete insulin cells—70% more in center—secrete insulin

(decreses blood sugar level).(decreses blood sugar level). αα cells---20% more in periphery—secrete glucagon cells---20% more in periphery—secrete glucagon

—increase blood glucose level.—increase blood glucose level. δδ cells---5%--secrete somatostatin—paracrine and cells---5%--secrete somatostatin—paracrine and

endocrine (reduce smooth muscle contraction).endocrine (reduce smooth muscle contraction). G cells---1%---secrete gastrin---increas HCl.G cells---1%---secrete gastrin---increas HCl. PP cells—1%---secrete pancreatic polypeptide—PP cells—1%---secrete pancreatic polypeptide—

inhibit exocrine pancreatic secretion.inhibit exocrine pancreatic secretion.

Islet of LangerhansIslet of Langerhans

Liver ( its unit is the classic liver Liver ( its unit is the classic liver lobule)lobule)

Portal triad (area)Portal triad (area)It houses:It houses:

1-branches of hepatic artery.

2-tributaries of portal vein.

3-interlobular bile ducts.

4-Lymph vessels.It is isolated from liver parenchyma by limiting plate of modified hepatocytes

Three concepts of liver lobulesThree concepts of liver lobules

1-Classic liver lobule---Bl. Flows from periphery toward central vein.

2-portal lobule---bile flows to a particular interlobular duct.

3-Hepatic (portal) acinus—in which three concentric regions of hepatocytes surrounding a distributing artery in the center.

Classic liver lobuleClassic liver lobuleIt is formed of anastomosing plates of hepatocytes of tow cells thick.

There are blood sinusoids between plates that separated from hepatocytes by perisinusoidal Space of Disse.

Space of Disse contains:

A- Plasma. B-Reticular fibers. C-fat storing cells (Ito cells). D-nonmyelinated nerve fibers. .E- Microvilli of hepatocytes. F-Pit cells (natural killer cells).

Hepatic sinusoidsHepatic sinusoids They have gap junctions.They have gap junctions. They have fenestrae.They have fenestrae. They show Kupffer cells, that originate from They show Kupffer cells, that originate from

monocytes (phagocytic) and rich in lysosomes monocytes (phagocytic) and rich in lysosomes and have filopodia-like projections.and have filopodia-like projections.

They receive blood from inlet arterioles and They receive blood from inlet arterioles and inlet venules.inlet venules.

Their blood flows into the central vein that give Their blood flows into the central vein that give sublobular ,then collecting veins to form hepatic sublobular ,then collecting veins to form hepatic veins.veins.

HepatocytesHepatocytes

Sinusoidal domainLateral domain

Hepatic ductsHepatic ducts Bile canaliculi that formed by hepatocytes cell Bile canaliculi that formed by hepatocytes cell

membranes.membranes. Bile canaliculi merge with cholangiole (short Bile canaliculi merge with cholangiole (short

tubules formed of a combination of tubules formed of a combination of hepatocytes, low cuboidal cells and oval cells).hepatocytes, low cuboidal cells and oval cells).

Bile from cholangioles enters canals of Hering Bile from cholangioles enters canals of Hering (branches of interlobular ducts).(branches of interlobular ducts).

Interlobular ducts are lined with simple cuboidal Interlobular ducts are lined with simple cuboidal epithelium.epithelium.

Interlobular ducts merge to form hepatic bile Interlobular ducts merge to form hepatic bile ducts.ducts.

Gall bladderGall bladder

It is composed of 4 layers.It is composed of 4 layers. 1-Simple columnar epithelium.1-Simple columnar epithelium. 2-vascularized loose CT lamina propria 2-vascularized loose CT lamina propria

that contains small mucous glands.that contains small mucous glands. Smooth muscle arranged as inner oblique Smooth muscle arranged as inner oblique

and outer longtudinal layers.and outer longtudinal layers. Serosal adventitia.Serosal adventitia.

Gall bladderGall bladder