PlacentaPlacenta

Hasu.chaudhariHasu.chaudhari

Placenta is the organ that facilitates Placenta is the organ that facilitates nutrient and gas exchange between nutrient and gas exchange between the maternal and fetal bloodthe maternal and fetal blood

Changes in the Changes in the TrophoblastTrophoblast The The fetal componentfetal component of the placenta is derived from the of the placenta is derived from the

trophoblasttrophoblast and and extraembryonic mesodermextraembryonic mesoderm ((chorionic platechorionic plate).).

The The maternal componentmaternal component is derived from the is derived from the endometriumendometrium..

By By 22ndnd month month, the trophoblast is characterised by , the trophoblast is characterised by number of number of secondarysecondary and and tertiary villitertiary villi..

Capillary system developing in the core of villous system Capillary system developing in the core of villous system soon comes in contact with capillaries of the chorionic soon comes in contact with capillaries of the chorionic plate and connecting stalk, forming plate and connecting stalk, forming extraembryonic extraembryonic vascular systemvascular system..

Maternal blood is delivered to placenta by Maternal blood is delivered to placenta by spiral arteriesspiral arteries in the uterus.in the uterus.

Changes in the TrophoblastChanges in the Trophoblast Cytotrophoblast cells invades the terminal ends of spiral Cytotrophoblast cells invades the terminal ends of spiral

arteries, replaces maternal endothelial cells by arteries, replaces maternal endothelial cells by undergoing undergoing epithelial to endothelial transitionepithelial to endothelial transition..

Numerous small extensions grow out from existing Numerous small extensions grow out from existing stem stem villivilli as as free villifree villi into the surrounding into the surrounding lacunar/intervillous spacelacunar/intervillous space..

By By 44thth month month cytotrophoblastic cells and some cytotrophoblastic cells and some connective tissue cells disappear.connective tissue cells disappear.

The The syncytiumsyncytium and the and the endothelial wallendothelial wall of the blood of the blood vessel are the only layers that separate the maternal and vessel are the only layers that separate the maternal and fetal circulations.fetal circulations.

Preeclampsia Preeclampsia : : hypertension, proteinuria and edema hypertension, proteinuria and edema during pregnancyduring pregnancy

Chorion frondosum and Decidua Chorion frondosum and Decidua basalisbasalis

Villi on the embryonic pole grow and expand giving Villi on the embryonic pole grow and expand giving rise to the rise to the Chorion frondosumChorion frondosum (bushy chorion) (bushy chorion)..

On the aembryonic pole it degenerates by On the aembryonic pole it degenerates by 33rdrd month month, , making the chorion smooth, known as making the chorion smooth, known as Chorion Chorion laevelaeve..

This difference is also reflected in decidua, the layer of the endometrium, which is shed during parturition.

The decidua over the chorion frondosum, the decidua basalis, have a compact layer of large cells, decidual cells, known as decidual plate, is tightly connected to the chorion.

The decidual layer over the abembryonic pole is the decidua capsularis which later degenerates.

Chorion frondosum and Decidua Chorion frondosum and Decidua basalisbasalis

Subsequently, the chorion laeve comes in contact with the uterine wall (decidua parietalis) on the opposite side, and the two fuse obliterating the uterine lumen.

Hence, the only portion of the chorion participating in the exchange process is the chorion frondosum, which, together with the decidua basalis, makes up the placenta.

Similarly, fusion of amnion and chorion to form the amniochorionic membrane obliterates the chorionic cavity. It is this membrane that ruptures during labor.

STRUCTURE OF THE PLACENTA Fetal portion: formed by the chorion frondosum Maternal portion: formed by the decidua basalis On the fetal side, the placenta is bordered by the

chorionic plate. On its maternal side, it is bordered by the decidua

basalis of which the decidual plate is most intimately incorporated into the placenta.

In the junctional zone, trophoblast and decidual cells intermingle.

Between the chorionic and decidual plates are the intervillous spaces, which are filled with maternal blood.

During the 4th and 5th months, the decidua forms a number of decidual septa, which project into intervillous spaces but do not reach the chorionic plate. It divides placenta into compartments known as Cotyledons.

Full-Term Placenta

It is discoid with a diameter of 15 to 25 cm, is approximately 3 cm thick, and weighs about 500 to 600 g.

It is expelled approximately 30 minutes after birth of the child.

When it is viewed from the maternal side, 15 to 20 slightly bulging areas, the cotyledons, are clearly recognizable.

The fetal surface is covered by the chorionic plate. Large arteries and veins, the chorionic vessels, converge toward the umbilical cord.

The chorion, in turn, is covered by the amnion. Attachment of the umbilical cord is usually

eccentric and occasionally even marginal.

Circulation of the Placenta Cotyledons receive blood through 80 to 100

spiral arteries and enter the intervillous spaces at more or less regular intervals.

Pressure in these arteries forces the blood deep into the intervillous spaces and bathes the numerous small villi of the villous tree in oxygenated blood.

As the pressure decreases, blood flows back from the chorionic plate toward the decidua, where it enters the endometrial veins.

The intervillous spaces of a mature placenta contain approximately 150 mL, replenished about 3-4 times per minute.

Placental exchange does not take place in all villi, however, only in those that have fetal vessels in intimate contact with overlying syncytial membrane.

Circulation of the Placenta Placental membranePlacental membrane which separates maternal which separates maternal

and fetal blood, is initially composed of and fetal blood, is initially composed of 4 layers4 layers::- Endothelial lining of fetal vesselsEndothelial lining of fetal vessels- Connective tissue in the villous coreConnective tissue in the villous core- Cytotrophoblastic layerCytotrophoblastic layer- SyncytiumSyncytium From From 44thth month month on, however the placental on, however the placental

membrane have only membrane have only 2 layers2 layers ( (placental placental barrierbarrier):):

- Endothelial lining of fetal vesselsEndothelial lining of fetal vessels- SyncytiumSyncytium

Erythroblastosis fetalisErythroblastosis fetalisFetal hydropsFetal hydrops

Hydrops fetalisHydrops fetalis

Function of placentaFunction of placenta Exchange of gasesExchange of gases Exchange of nutrients and electrolytesExchange of nutrients and electrolytes Transmission of maternal antibodies (IgG)- Transmission of maternal antibodies (IgG)-

passive immunitypassive immunity Hormone production : by syncytial trophoblastHormone production : by syncytial trophoblast- Progesterone: by 4Progesterone: by 4thth month month- Estrogenic hormone (estriol) – uterine growth Estrogenic hormone (estriol) – uterine growth

and development of mammary glandand development of mammary gland- Human chorionic gonadotropin (hCG)- for first 2 Human chorionic gonadotropin (hCG)- for first 2

monthsmonths- Somatomammotropin- makes mother Somatomammotropin- makes mother

diabetogenic and promotes breast development diabetogenic and promotes breast development for milk productionfor milk production

Amnion and umbilical cordAmnion and umbilical cord The oval line of reflection between the amnion and The oval line of reflection between the amnion and

embryonic ectoderm is the embryonic ectoderm is the primitive umbilical ringprimitive umbilical ring.. At At 55thth week week, following structures pass through it:, following structures pass through it:- Connecting stalk, containing allantois and umbilical Connecting stalk, containing allantois and umbilical

vessels (2 arteries and 1 vein)vessels (2 arteries and 1 vein)- Yolk stalk (vitelline duct) with vitelline vesselsYolk stalk (vitelline duct) with vitelline vessels- Canal connecting the intraembryonic and Canal connecting the intraembryonic and

extraembryonic cavities.extraembryonic cavities. At At 33rdrd month month, amnion has expanded so that it comes in , amnion has expanded so that it comes in

contact with chorion, obliterating the chorionic cavity.contact with chorion, obliterating the chorionic cavity. Yolk sac then usually shrinks and is gradually Yolk sac then usually shrinks and is gradually

obliteratedobliterated At the end of At the end of 33rdrd month month, allantois, vitelline duct and its , allantois, vitelline duct and its

vessels are obliterated.vessels are obliterated. Now the cord contains only Now the cord contains only umbilical vesselsumbilical vessels

surrounded by surrounded by Wharton’s jellyWharton’s jelly..

PLACENTAL CHANGES AT THEEND OF PREGNANCY

Increase in fibrous tissue in the core of villus

Thickening of basement membranes in fetal capillaries

Obliterative changes in small capillaries of villi

Deposition of fibrinoid on the surface of the villi in the junctional zone and chorionic plate

Amniotic fluidAmniotic fluid It is the clear, watery fluid filling the amniotic It is the clear, watery fluid filling the amniotic

cavity, produced in part by cavity, produced in part by amniotic cellsamniotic cells and and derived primarily from derived primarily from maternal bloodmaternal blood..

Approximately 30 ml at 10 weeks, 450 ml at 20 Approximately 30 ml at 10 weeks, 450 ml at 20 weeks and weeks and 800-1000 ml800-1000 ml at 37 weeks of at 37 weeks of gestation.gestation.

It absorbs jolt, prevents adherence of embryo to It absorbs jolt, prevents adherence of embryo to the amnion and allows fetal movements.the amnion and allows fetal movements.

Its volume is replaced every 3 hours.Its volume is replaced every 3 hours. From 5From 5thth month fetus swallows it own amniotic month fetus swallows it own amniotic

fluid, about 400 ml/day.fluid, about 400 ml/day. Fetal urine is added daily to the amniotic fluid in Fetal urine is added daily to the amniotic fluid in

55thth month. month.

Twins : Dizygotic twins Twins : Dizygotic twins

Monozygotic twinsMonozygotic twins

Twin defects : Conjoined twinsTwin defects : Conjoined twins

Parturition (Birth)Parturition (Birth)

Divided into Divided into three stagesthree stages::

1.1. Stage 1: effacement (thinning and Stage 1: effacement (thinning and shortening) and full dilatation of shortening) and full dilatation of cervixcervix

2.2. Stage 2 : delivery of the fetusStage 2 : delivery of the fetus

3.3. Stage 3 : delivery of placenta Stage 3 : delivery of placenta

Menstrual cycleMenstrual cycle It is the It is the cyclical changescyclical changes that occurs in that occurs in

the uterus (the uterus (endometriumendometrium) every month.) every month. Reproductive periodReproductive period – period in a – period in a

woman’s life in which she can bear childrenwoman’s life in which she can bear children MenstruationMenstruation – monthly flow of blood from – monthly flow of blood from

uterusuterus MenarcheMenarche – onset of menstruation (at – onset of menstruation (at

about 12 yrs)about 12 yrs) MenopauseMenopause – cessation of menstruation (at – cessation of menstruation (at

about 45 yrs) about 45 yrs) Cyclical changes that takes place in the Cyclical changes that takes place in the

ovaries is known as ovaries is known as ovarian cycleovarian cycle..

Structure of uterine wallStructure of uterine wall Perimetrium – outermost layer, made up Perimetrium – outermost layer, made up

of peritoneumof peritoneum Myometrium – middle layer, made up of Myometrium – middle layer, made up of

smooth musclesmooth muscle Endometrium – innermost layer, mucous Endometrium – innermost layer, mucous

membrane. It is this layer which membrane. It is this layer which undergoes cyclical changes during undergoes cyclical changes during menstrual cyclemenstrual cycle

Structure of uterine wallStructure of uterine wall

Constituents of endometriumConstituents of endometrium

Surface covered by lining epitheliumSurface covered by lining epithelium Stroma contains numerous simple Stroma contains numerous simple

tubular glands (uterine glands)tubular glands (uterine glands) Spiral arteries supply the whole Spiral arteries supply the whole

thickness , while straight arteries are thickness , while straight arteries are confined to the basal part of confined to the basal part of endometriumendometrium

Phases of menstrual cyclePhases of menstrual cycle

On the basis of changes taking place in On the basis of changes taking place in the endometrium it is divided into:the endometrium it is divided into:

1.1. Postmentstrual phasePostmentstrual phase2.2. Proliferative phaseProliferative phase3.3. Secretory phaseSecretory phase4.4. Menstrual phaseMenstrual phase

Also classified as:Also classified as:1.1. Follicular phaseFollicular phase2.2. Luteal phaseLuteal phase

Menstrual

Post menstrual

Proliferative

Secretory

Phases of menstrual cyclePhases of menstrual cycle

Follicular phaseFollicular phase

It constitutes the first half of the It constitutes the first half of the menstrual period.menstrual period.

The changes in this phase takes The changes in this phase takes place under the influence of place under the influence of oestrogen produced by the oestrogen produced by the developing follicle.developing follicle.

Luteal phaseLuteal phase

It constitutes the second half of the It constitutes the second half of the menstrual period.menstrual period.

The changes in this phase takes The changes in this phase takes place under the influence of place under the influence of progesterone produced by the progesterone produced by the corpus luteum, along with corpus luteum, along with oestrogen.oestrogen.

The changes during menstrual cycle are The changes during menstrual cycle are summarized as follow:summarized as follow:

Endometrium increases in thicknessEndometrium increases in thickness- Postmentrual phase: 0.5-1 mmPostmentrual phase: 0.5-1 mm- Proliferative phase: 2-3 mmProliferative phase: 2-3 mm- Secretory phase: 5-7 mmSecretory phase: 5-7 mm■ Uterine gland grow in length and becomes convolutedUterine gland grow in length and becomes convoluted■ Lining epithelium of the glands changesLining epithelium of the glands changes- cuboidal in postmenstrual phasecuboidal in postmenstrual phase- columnar during proliferative phase and columnar during proliferative phase and - apical part of cell is shed of during secretory phaseapical part of cell is shed of during secretory phase■ As the endometrium increases in thickness, stroma is As the endometrium increases in thickness, stroma is

divided intodivided into- Stratum compactumStratum compactum- Stratum spongiosumStratum spongiosum- Stratum basaleStratum basale

The changes during menstrual cycle are The changes during menstrual cycle are summarized as follow:summarized as follow:

■ Arteries grow in length during proliferative stage.Arteries grow in length during proliferative stage.■ During secretory phase, arteries supplying the During secretory phase, arteries supplying the

superficial 2/3superficial 2/3rdrd becomes tortous called becomes tortous called spiral arteriesspiral arteries and arteries to the basal 3and arteries to the basal 3rdrd remains straight. remains straight.

Towards the end of secretory phase endometrium is Towards the end of secretory phase endometrium is thick, soft and richly suppied with blood.thick, soft and richly suppied with blood.

In the absence of pregnancy, the superficial parts of the In the absence of pregnancy, the superficial parts of the endometrium( stratum compactum and stratum endometrium( stratum compactum and stratum spongiosum) are shed off as menstrual bleeding.spongiosum) are shed off as menstrual bleeding.

Just before the onset of bleeding, there is lowering of Just before the onset of bleeding, there is lowering of both progesterone and oestrogen, and it is believed that both progesterone and oestrogen, and it is believed that this withdrawal leads to onset of menstual bleeding.this withdrawal leads to onset of menstual bleeding.

At the end of menstruation the endometrium that At the end of menstruation the endometrium that remains consists of stratum basale and the basal remains consists of stratum basale and the basal portion of uterine glands.portion of uterine glands.

Hormonal control of ovarian and Hormonal control of ovarian and menstrual cyclemenstrual cycle Hypothalamus secretes Gonadotropin releasing hormoneHypothalamus secretes Gonadotropin releasing hormone

Stimulates anterior pituitary to secrete gonadotropic Stimulates anterior pituitary to secrete gonadotropic hormones i.e., follicle stimulating hormone (FSH) and hormones i.e., follicle stimulating hormone (FSH) and luteinizing hormone (LH).luteinizing hormone (LH).

In turn FSH acts on the ovary and stimulates formation and In turn FSH acts on the ovary and stimulates formation and maturation of ovarian follicles.maturation of ovarian follicles.

Maturing ovarian follicles secretes oestrogen, which causes Maturing ovarian follicles secretes oestrogen, which causes repair and proliferation of endometrium.repair and proliferation of endometrium.

Two days before ovulation, oestrogen level rises to maximum, Two days before ovulation, oestrogen level rises to maximum, leading to sudden increase on LH level (LH surge).leading to sudden increase on LH level (LH surge).

Ovulation takes place and corpus luteum is formed.Ovulation takes place and corpus luteum is formed. LH stimulates secretion of progesterone by corpus luteum.LH stimulates secretion of progesterone by corpus luteum. In the absence of fertilization, granulosa cells produce inhibin, In the absence of fertilization, granulosa cells produce inhibin,

which inhibits gonadotropin secretion from anterior pituitary.which inhibits gonadotropin secretion from anterior pituitary. Regresses corpus luteum, fall in oestrogen and progesterone, Regresses corpus luteum, fall in oestrogen and progesterone,

this withdrawal of hormone triggers onset of menstraution.this withdrawal of hormone triggers onset of menstraution.

Time of ovulationTime of ovulation In a 28 days cycle, ovulation takes place at In a 28 days cycle, ovulation takes place at

about the middle of the cycle.about the middle of the cycle.

The period between ovulation and the next The period between ovulation and the next menstrual bleeding is constant at about 14 menstrual bleeding is constant at about 14 days.days.

One commonly used method to find out One commonly used method to find out ovulation is ovulation is temperature methodtemperature method. At the middle . At the middle of the cycle there is sudden fall in temperature of the cycle there is sudden fall in temperature followed by rise. This rise is believed to indicate followed by rise. This rise is believed to indicate ovulation.ovulation.

Safe periodSafe period It is the period during one menstrual cycle in It is the period during one menstrual cycle in

which despite unprotected intercourse which despite unprotected intercourse fertilization may not occur.fertilization may not occur.

Menstrual cycle : 28+2 days or 28-2 days.Menstrual cycle : 28+2 days or 28-2 days.

Safe period calculation:Safe period calculation:Shortest cycle minus 20 days : 26-20 = 6Shortest cycle minus 20 days : 26-20 = 6thth day dayLongest cycle minus 10 days : 30-10 = 20Longest cycle minus 10 days : 30-10 = 20thth day dayThus from 6Thus from 6thth to 20 to 20thth day of each cycle day of each cycle

counting from first day of menstrual period counting from first day of menstrual period is considered as fertile period. is considered as fertile period.

Development of Development of Gastrointestinal tractGastrointestinal tract

General introductionGeneral introduction Epithelial lining is Epithelial lining is

endodermalendodermal in origin in origin At the mouth and anus At the mouth and anus

epithelium is epithelium is ectodermalectodermal.. As a result of cephalocaudal

and lateral folding, a portion of the endoderm-lined yolk sac cavity is incorporated into the embryo to form the primitive gut.

In the cephalic and caudal parts of the embryo, the primitive gut forms a blind-ending tube, the foregut and hindgut, respectively. The middle part, the midgut, remains temporally connected to the yolk sac by means of the vitelline duct, or yolk stalk

General introductionGeneral introduction Development of the primitive gut is divided as follow:a. The pharyngeal gut, or pharynx, extends from the

oropharyngeal membrane to the respiratory diverticulum, part of foregut.

b. The remainder of the foregut lies caudal to the pharyngeal tube and extends as far caudally as the liver outgrowth.

c. The midgut begins caudal to the liver bud and extends to the junction of the right two-thirds and left third of the transverse colon in the adult.

d. The hindgut extends from the left third of the transverse colon to the cloacal membrane.

Endoderm forms the epithelial lining of the digestive tract and gives rise to the specific cells (the parenchyma) of glands, such as hepatocytes and the exocrine and endocrine cells of the pancreas.

The stroma (connective tissue) for the glands is derived from visceral mesoderm.

Muscle, connective tissue, and peritoneal components of the wall of the gut also are derived from visceral mesoderm.

DERIVATIVES OF FOREGUTDERIVATIVES OF FOREGUT 1)1) Part of the floor of the mouth including the tongue.Part of the floor of the mouth including the tongue.

2)2) PharynxPharynx3)3) Various derivatives of the pharyngeal pouches and Various derivatives of the pharyngeal pouches and

the thyroid.the thyroid.4)4) OesophagusOesophagus5)5) StomachStomach6)6) Duodenum- whole of the superior part and upper Duodenum- whole of the superior part and upper

half of descending part (upto major duodenal half of descending part (upto major duodenal papilla)papilla)

7)7) Liver and extra hepatic biliary systemLiver and extra hepatic biliary system8)8) PancreasPancreas9)9) Respiratory system. Respiratory system.

DERIVATIVES OF MIDGUTDERIVATIVES OF MIDGUT

1.1. Duodenum- descending part distal to Duodenum- descending part distal to major papilla, horizontal and major papilla, horizontal and ascending parts.ascending parts.

2.2. JejunumJejunum

3.3. Ileum Ileum

4.4. Caecum and appendixCaecum and appendix

5.5. Ascending colonAscending colon

6.6. Right 2/3 of the transverse colon Right 2/3 of the transverse colon

DERIVATIVES OF HIND GUTDERIVATIVES OF HIND GUT

11 Left 1/3 of the transverse colonLeft 1/3 of the transverse colon

22 Descending and pelvic colonDescending and pelvic colon

33 RectumRectum

44 Upper part of anal canalUpper part of anal canal

55 Parts of urogenital system developed Parts of urogenital system developed from primitive urogenital sulcus. from primitive urogenital sulcus.

Arteries of GutArteries of Gut

Foregut – Foregut – Coeliac arteryCoeliac artery Midgut – Midgut – Superior mesenteric arterySuperior mesenteric artery Hindgut – Hindgut – Inferior mesenteric arteryInferior mesenteric artery

Note:Note: The endodermal tube only gives rise to The endodermal tube only gives rise to the lining epithelium of G.I.T.the lining epithelium of G.I.T.The submucous coat, muscular coat, serous The submucous coat, muscular coat, serous coat are all developed from splanchnopleuric coat are all developed from splanchnopleuric layer of lateral part of mesoderm. layer of lateral part of mesoderm.

MESENTERIES Double layers of peritoneum that enclose an organ and connect

it to the body wall, such organs are called intraperitoneal. Organs that lie against the posterior body wall and are covered

by peritoneum on their anterior surface only (e.g., the kidneys) are called retroperitoneal.

Peritoneal ligaments are double layers of peritoneum (mesenteries) that pass from one organ to another or from an organ to the body wall.

Caudal part of the foregut, the midgut, and a major part of the hindgut are suspended from the abdominal wall by the dorsal mesentery.

Ventral mesentery, which exists only in the region of the terminal part of the esophagus, the stomach, and the upper part of the duodenum, is derived from the septum transversum.

Growth of liver in the mesenchyme of septum transversum divides the ventral mesentery into:

a. Lesser omentum, extending from the lower portion of the esophagus, the stomach, and the upper portion of the duodenum to the liver

b. Falciform ligament, extending from the liver to the ventral body wall

Derivation of individual parts of Derivation of individual parts of alimentary tractalimentary tract

Esophagus: At the 4th week of development a respiratroy

diverticulum (lung bud) appears at the ventral wall of foregut (between pharynx & stomach).

Separated from the foregut by tracheoesophageal septum.

Foregut then divides into dorsal portion oesophagus and ventral portion respiratory primordium.

Muscle coat, formed by the surrounding splanchnic mesenchyme, is straited in its upper 2/3rd (vagus) and smooth in the lower 1/3rd (splanchnic plexus)

Congenital anomaly: Esophageal AtresiaCongenital anomaly: Esophageal Atresiawith Tracheoesophageal (TE) Fistulawith Tracheoesophageal (TE) Fistula

StomachStomach At 4At 4thth week it appears as a week it appears as a fusiform dilatationfusiform dilatation..

Dorsally attached to Dorsally attached to dorsal mesogastriumdorsal mesogastrium..

Vertrally attached to Vertrally attached to septum transversumseptum transversum by by ventral ventral mesogastriummesogastrium..

Liver and the diaphragm are formed in the substance Liver and the diaphragm are formed in the substance of septum transversum.of septum transversum.

Ventral mesogastrium form Ventral mesogastrium form lesser omentumlesser omentum, , coronary coronary ligamentligament and and falciform ligamentfalciform ligament..

The dorsal mesogastrium is divided by the developing The dorsal mesogastrium is divided by the developing spleen to form the spleen to form the gastrosplenic ligamentgastrosplenic ligament and and lienorenal ligamentlienorenal ligament..

StomachStomach It rotates around It rotates around longitudinal longitudinal and and antero-posterior axisantero-posterior axis

respectively during development.respectively during development. Undergoes differential growth resulting in alteration in its Undergoes differential growth resulting in alteration in its

shape and orientation.shape and orientation.

Ventral border comes to face upward, becomes lesser Ventral border comes to face upward, becomes lesser curvature.curvature.

Dorsal border points downwards & to the left, becomes Dorsal border points downwards & to the left, becomes greater curvature.greater curvature.

Rotation about the longitudinal axis pulls the dorsal mesogastrium to the left, creating a space behind the stomach called the omental bursa (lesser peritoneal sac).

As it rotates around anteroposterior axis, the dorsal mesogastrium bulges down, continues to grow down and forms a double-layered sac extending over the transverse colon and small intestinal loops like an apron, called greater omentum.

Congenital anomaly: Congenital Congenital anomaly: Congenital pyloric stenosispyloric stenosis

Duodenum:Duodenum: Derived from Derived from terminal part of foregutterminal part of foregut and and

cephalic part of midgutcephalic part of midgut..

Liver bud present at the Junction.Liver bud present at the Junction.

Due to the Due to the rotation rotation of stomach, the duodenum of stomach, the duodenum form a C- shaped loop & rotates to the right.form a C- shaped loop & rotates to the right.

Rapid growth of head of pancreas pushes Rapid growth of head of pancreas pushes duodenum to the right side of abdominal cavity.duodenum to the right side of abdominal cavity.

Its Its proximal partproximal part is supplied by branches from is supplied by branches from coeliac arterycoeliac artery and and distal partdistal part by branches from by branches from superior mesenteric arterysuperior mesenteric artery..

Congenital anomaly: Congenital anomaly: Duodenal stenosis and Atresia

Jejunum and IleumJejunum and Ileum

Jejunum & ileum are derived from pre-arterial Jejunum & ileum are derived from pre-arterial segment of mid gut loop.segment of mid gut loop.

Terminal portion of the ileum is derived from Terminal portion of the ileum is derived from the post arterial segment proximal to the the post arterial segment proximal to the caecal bud.caecal bud.

Caecum and appendixCaecum and appendix Caecum and appendix are derived from Caecum and appendix are derived from

enlargement of caecal bud.enlargement of caecal bud. Caecal bud is a diverticulum arising from the Caecal bud is a diverticulum arising from the

post arterial segment of mid gut loop.post arterial segment of mid gut loop. Proximal part grows rapidly to form caecum.Proximal part grows rapidly to form caecum. Distal part remains narrow and form the Distal part remains narrow and form the

appendix.appendix.

Ascending colonAscending colon Derived from post arterial segment of mid gut loop Derived from post arterial segment of mid gut loop

distal to caecal bud.distal to caecal bud.

Transverse colonTransverse colon Right 2/3Right 2/3rdrd develops from post arterial segment of mid develops from post arterial segment of mid

gut loop.gut loop. Left 1/3Left 1/3rdrd develops from hind gut. develops from hind gut. Right 2/3Right 2/3rdrd supplied by superior mesenteric artery. supplied by superior mesenteric artery. Left 1/3Left 1/3rdrd by inferior mesenteric artery. by inferior mesenteric artery.

Descending colonDescending colon Develops from hind gutDevelops from hind gut

Rectum Rectum Derived from the Derived from the primitive rectumprimitive rectum, i.e., the dorsal , i.e., the dorsal

subdivision of the cloacasubdivision of the cloaca

CloacaCloaca : part of the hind gut caudal to the attachment : part of the hind gut caudal to the attachment of allantoic diverticulum.of allantoic diverticulum.

Cloaca is subdivided by a urorectal septum into:Cloaca is subdivided by a urorectal septum into:- Ventral part (Ventral part (primitive urogenital sinusprimitive urogenital sinus))- Dorsal part (Dorsal part (primitive rectumprimitive rectum).).

Cloacal membrane is divided by the urorectal septum Cloacal membrane is divided by the urorectal septum into ventral into ventral urogenital membraneurogenital membrane and dorsal and dorsal anal anal membranemembrane..

Congenital anomalies:Congenital anomalies: Rectal fistula: Rectal fistula: rectovesicalrectovesical, , rectourethral, rectovaginal, or sometime combination of rectourethral, rectovaginal, or sometime combination of

more than one type.more than one type.

Anal canalAnal canal

Partly from the Partly from the endoderm of primitive endoderm of primitive rectum and partly from rectum and partly from ectodermectoderm

The line of junction of The line of junction of endoderm and endoderm and ectoderm is ectoderm is represented by anal represented by anal valves (valves (pectinate linepectinate line))

Congenital anomaly:Congenital anomaly: Imperforate anusImperforate anus

Rotation of gutRotation of gut The The mid gut loopmid gut loop after formation lies outside the after formation lies outside the

abdominal cavity.abdominal cavity. The loop has The loop has prearterialprearterial (cephalic) segment and (cephalic) segment and

postarterialpostarterial (caudal) segment. (caudal) segment. Initially the loop lies in the Initially the loop lies in the sagittal planesagittal plane, ,

proximal segment being cranial and ventral to proximal segment being cranial and ventral to distal segment.distal segment.

The loop undergoes an The loop undergoes an anticlockwise rotationanticlockwise rotation by by 909000, so that it lies in , so that it lies in horizontal planehorizontal plane..

Now prearterial segement lies on right side and Now prearterial segement lies on right side and postarterial segment on the left.postarterial segment on the left.

Coils of jejunum and ileum (prearterial segment), Coils of jejunum and ileum (prearterial segment), as they return to abdominal cavity, undergoes a as they return to abdominal cavity, undergoes a further further anticlockwise rotation.anticlockwise rotation.

Rotation of gutRotation of gut So that coils of jejunum and ileum pass behind So that coils of jejunum and ileum pass behind

superior mesenteric arterysuperior mesenteric artery into the left half of into the left half of abdominal cavity.abdominal cavity.

Finally postarterial segment returns to the Finally postarterial segment returns to the abdominal cavity undergoing abdominal cavity undergoing anticlockwise anticlockwise rotationrotation..

As a result, transverse colon lies anterior to the As a result, transverse colon lies anterior to the superior mesenteric arterysuperior mesenteric artery and caecum lie on and caecum lie on right side.right side.

Gradually caecum descends to the iliac fossa Gradually caecum descends to the iliac fossa and ascending, transverse and descending and ascending, transverse and descending parts of colon become distinct. parts of colon become distinct.

Anomalies Associated with Malrotation: Anomalies Associated with Malrotation: Non Non rotation, Volvulus, Reverse rotation, subhepatic rotation, Volvulus, Reverse rotation, subhepatic

caecum, Omphalocelecaecum, Omphalocele

Development of Liver ,pancreas Development of Liver ,pancreas and spleenand spleen

Hepatic bud or hepatic diverticulum arise from Hepatic bud or hepatic diverticulum arise from the junction between foregut and hind gut.the junction between foregut and hind gut.

Pass through the ventral mesogastrium into Pass through the ventral mesogastrium into septum transversum.septum transversum.

Elongates and divide to form pars hepatica and Elongates and divide to form pars hepatica and pars cystica.pars cystica.

Pars hepatica gives rise to the parenchyma of Pars hepatica gives rise to the parenchyma of liver and bile capillaries.liver and bile capillaries.

The connective tissue of liver is derived from The connective tissue of liver is derived from the septum transversum.the septum transversum.

The gall bladder and the cystic duct are The gall bladder and the cystic duct are developed from the pars cystica.developed from the pars cystica.

Hepatic bud proximal to the pars cystica will Hepatic bud proximal to the pars cystica will form the bile duct.form the bile duct.

Anomalies of liver and gall Anomalies of liver and gall bladderbladder

Formation of Formation of accessory lobe and accessory lobe and abnormal lobes.abnormal lobes.

Gall bladder may be Gall bladder may be partially divided partially divided

Gall bladder may be Gall bladder may be duplicated.duplicated.

PancreasPancreas Two endodermal buds: dorsal and ventral buds arise Two endodermal buds: dorsal and ventral buds arise

from the gut that later forms 2from the gut that later forms 2ndnd part of duodenum. part of duodenum. Ventral bud shifts to the left side.Ventral bud shifts to the left side. The ventral bud form the uncinate process and the The ventral bud form the uncinate process and the

lower part of head.lower part of head. The dorsal bud form the upper part of head , body and The dorsal bud form the upper part of head , body and

tail. tail. The ducts of the ventral and the dorsal bud The ducts of the ventral and the dorsal bud

anastomose.anastomose. The duct of the dorsal bud between the anastomosis The duct of the dorsal bud between the anastomosis

and the duodenum – accessory pancreatic duct.and the duodenum – accessory pancreatic duct. Main pancreatic duct – distally by duct of dorsal bud Main pancreatic duct – distally by duct of dorsal bud

and proximally by duct of ventral budand proximally by duct of ventral bud Islets of langerhans – derived from primitive duct Islets of langerhans – derived from primitive duct

system.system.

Congenital anomalies in pancreasCongenital anomalies in pancreas Annular pancreasAnnular pancreas Divided pancreasDivided pancreas

Development of SpleenDevelopment of Spleen Mesenchymal cells of Mesenchymal cells of

dorsal mesogastrium dorsal mesogastrium proliferate forming the proliferate forming the spleen.spleen.

Pass to the left side.Pass to the left side. Dorsal mesogastrium Dorsal mesogastrium

gives rise to gives rise to gastrosplenic and gastrosplenic and linorenal ligament.linorenal ligament.

Congenital OmphaloceleCongenital OmphaloceleHerniation of abdominal viscera through the umbilical ring. Failure of returning the bowel after physiological hernia.

Meckel’s (Ileal) DiverticulumMeckel’s (Ileal) Diverticulum•Persistance of vitellointestinal duct: 2%; 2”; 2ft. away from antimesenteric border of ileum.• Ulceration, bleeding or perforation may take place.

Congenital anomalies of the GutCongenital anomalies of the Gut Atresia.Atresia. StenosisStenosis Megacolon or Megacolon or

Hirschsprung’s Hirschsprung’s disease.disease.

(non development of nerve (non development of nerve plexus in the wall of plexus in the wall of gut).gut).