DEVELOPMENT OF COELOM OR BODY CAVITIESDr Iram Iqbal

THE PRIMITIVE COELOMOriginally the coelom of the animals was used as a temporary reservoir for excretory wastes. But this function has been superseded in vertebrates so that it now serves as a large bursa to permit frictionless movement of the heart, lungs and abdominal viscera.

12/02/2010

2

The coelom permits the visceral organs to grow and shift position without hindrance. The heart, lungs and abdominal organs of mammmals occupy separate coelomic compartments, whose respective linings are named pericardium, pleura and peritonium.

12/02/2010

3

The first occurrence of a body cavity in early human stages is in the extraembryonic mesoderm which lies between the embryo proper and the primitive chorionic capsule.(11 -12 DAY)th th

12/02/2010

4

12/02/2010

5

INTRAEMBRYONIC COELOM In the end of 3rd week intraembryonic mesoderm on each side of midline differentiates into paraxial portion, an intermediate portion and a lateral plate. When intercellular clefts appear in the lateral mesoderm, the plates are divided into two layers ;the somatic mesoderm layer and the splanchnic mesoderm layer.

12/02/2010

6

The future peritoneal cavity communicates broadly with the extra-embryonic coelom of each side.

12/02/2010

7

12/02/2010

8

As the embryo continues its folding and elongation, the peritoneal chamber is separated progressively from the extraembryonic coelom; the last region of closure is at the site of the developing umblical cord.

12/02/2010

9

12/02/2010

10

As the gut & the abdominal wall folds off, the primitive ventral mesentry is lost and the right and left temporary cavities become a single, common chamber. At the end of this early period the coelomic system thus consists of a single pericardial cavity & a single peritoneal cavity, interconnected by a pair of pleural canals.12/02/2010 11

A: HORSESHOE-SHAPED INTRAEMBRYONIC COELOM

A large intraembryonic cavity extending from thoracic to pelvic region forms 12/02/2010 12

12/02/2010

13

Serous membrane Cells of somatic mesoderm lining the intraembryonic cavity become mesothelial & form the parietal layer of the serous membranes lining the outside of the peritoneal ,pleural and pericardial cavities. Cells of the splanchnic mesoderm layer form the visceral layer of the serous membranes covering the abdominal organs ,lungs and heart12/02/2010 14

12/02/2010

15

DIVISIONS OF PRIMITIVE COELOM The division of the continuous, primitive coelom into separate, permanent cavities is accopmlished through the development of the three sets of partitions:

SEPTUM TRANSVERSUM PLEURO-PERICARDIAL MEMBRANES PLEURO-PERITONEAL MEMBRANES12/02/2010 16

SEPTUM TRANSVERSUM

Unpaired

Early, partial diaphragm

PLEURO-PERICARDIAL MEMBRANES

Paired

Join the septum

Complete the division between pericardial & pleural cavities

PLEURO-PERITONEAL MEMBRANESPairedUnite with the septumComplete the partition between pleural & peritoneal cavities

12/02/2010

17

SEPTUM TRANSVERSUMnsplit mass of mesoderm Transverse partition between the pericardial & abdominal cavities. Occupies space between the gut, yolk stalk & ventral body wall.The septum does not separate the thoracic and abdominal cavities completely but leave large openings the pericardioperitoneal canals on each side of forgut12/02/2010 18

12/02/2010

19

PLEURO-PERICARDIAL MEMBRANESIn a 4mm. Embryo the lungs begin to develop within the medial mass of mesenchyme that separates the two pleural canals. As a result of the rapid growth of the lungs, the pericardioperitoneal canals become too small, & the lungs begin to expand into the mesenchyme of the body wall dorsally, laterally, & ventrally, & soon bulge into them.12/02/2010 20

12/02/2010

21

The canals thereby become the potential pleural cavities. Ventral & lateral expansion is posterior to the pleuro-pericardial folds. At first, these folds appears as small ridges projecting into the primitive undivided thoracic cavity.12/02/2010 22

With expansion of the lungs, mesoderm of the body wall splits into two components:A) the definitive wall of the thorax B) pleuro-pericardial membranes, which are the extensions of the pleuro-pericardial folds that contain the common cardinal veins & phrenic nerves

Subsequently, the heart decends & the positional changes of the sinus venosus shift the common cardinal veins toward the midline. 12/02/2010

23

12/02/2010

24

THE PERICARDIUMThe pleuro-pericardial membranes are drawn out in a mesentry-like fashion. Finally, they fuse with each other & with the root of the lungs. The thoracic cavity is divided into the definitive pericardial cavity & two pleural cavities. In the adult, the pleuro-pericardial membranes form the fibrous pericardium.12/02/2010 25

A: 5 WEEKS

B: 6 WEEKS

C: 7 WEEKS12/02/2010

D: 8 WEEKS26

PLEURO-PERITONEAL MEMBRANES (formation of diaphragm)Although the pleural cavities are separate from the pericardial cavity, they remain in open communication with the abdominal (peritoneal) cavity. During further development, the opening between them is closed by cresent-shaped folds, the pleuro-peritoneal folds, which project into the caudal end of the pericardioperitoneal canals.12/02/2010 27

12/02/2010

28

Gradually, the folds extend medially & ventrally, so that by the 7th week, they fuse with the mesentry of the esophagus & with the septum transversum. Hence, the connection between the pleural & peritoneal portions of the body cavity is closed by the pleuro-peritoneal membranes.

12/02/2010

29

Further expansion of the pleural cavities relative to mesenchyme of the body wall add a peripheral rim to the pleuroperitoneal membranes. Once rim is established myoblasts originating in the body wall penetrates the membranes to form the muscular part of diaphragm.

12/02/2010

30

THE DIAPHRAGMDiaphragm is derived from four sources, but the limits of these several contributions cannot be set exactly. 1. septum transversum forms the central tendon of the diaphragm. 2. Small intermediate portions from the paired pleuro-peritoneal membranes. 3. Muscular components from the lateral and dorsal body wall. 4. Mesentry of the esophagus in which crura of the diaphragm develop12/02/2010

31

12/02/2010

32

5TH WEEK

12/02/2010

33

7TH WEEK

12/02/2010

34

4TH MONTH

12/02/2010

35

12/02/2010

36

12/02/2010

37

The septum transversum lies opposite cervical segments during the 4th week By the 6th week, the developing diaphragm is at the level of the thoracic somites. The repositioning of the diaphragm is caused by rapid growth of the dorsal part of the embryo (vertebral column), compared with that of the ventral part. By the beginning of the 3rd month, some of the dorsal bands of the diaphragm originate at the level of the 1st lumber vertebra.12/02/2010 38

POSITIONAL CHANGES OF THE DEVELOPING DIAPHRAGM

A: 24 DAYS12/02/2010

B: 41 DAYS

C: 52 DAYS39

NERVE SUPPLY OF THE DIAPHRAGMPHRENIC NERVE: Motor & sensory innervation LOWER INTERCOSTAL (THORACIC) NERVES: Sensory fibers to the peripheral part of the diaphragm

12/02/2010

40

Mesentry Development

Mesentery is a double layer of peritoneum that enclose an organ and connect it to the body wall

Provide pathways for vessels, nerves and lymphatics

12/02/2010

43

Part

f

l

i

GIPharyngeal gut Fore gut Mid gut Hind gut

12/02/2010

45

Mesenter

evel

ent During embryonic development digestive tract and accessory organs are suspended in peritoneal cavity by: dorsal mesentery ventral mesentery

THE DORSAL MESENTERY Extends from lower end of esophagus to the cloacal region of the hind gut Derived from splanchnic mesoderm In region of stomachThe dorsal mesogastrium or greater omentum Duodenum-The dorsal mesoduodenum Jejunum & ileummesentery proper Colon- The dorsal mesocolon12/02/2010

47

Ventral mesentery

12/02/2010

48

Mesenteries of the Stomach

12/02/2010

50

Primitive Dorsal Mesogastrium

12/02/2010

51

Appearance of the Omental Bursa

12/02/2010

52

12/02/2010

53

Development of Spleen

12/02/2010

54

El s t

ti ft stri t l rs

rs l si f

12/02/2010

55

Formation of

reater Omentum

12/02/2010

56

Mesentr

f

enum

Rotation of stomach causes C shaped duodenum and it rotates to the left.

Duodenum and pancreas become retroperitoneal, Except for Duodenal Cap.12/02/2010 58

Mesentry of Liver

12/02/2010

59

Mesentry of Pancreas

12/02/2010

60

Mesentries f mi

ut R tati n f intestinal l p cause twist in rsal mesentry. Ascending c l n bec mes Retr per t neal. Transverse Mes c l n fuses with p steri r wall f Greater Omentum

12/02/2010

62

12/02/2010

63

12/02/2010

64

Mesentry of Hindgut

Dorsal Mesentry forms Sigmoid Mesocolon. Rectum is only partially covered by the peritoneum.

12/02/2010

65

Mesenteries of Digestive Organs

12/02/2010

66

REFERENCES:Developmental Anatomy, A Textbook and Laboratory Manual of Embryology By LESLIE BRAINERD AREY, Revised 7th Edition LANGMANS Embryology 10th Edition, By T.W.SADLER The Developing Human, Clinically Oriented Embryology by KEITH L. MOORE, 8th Edition Google Search for Images12/02/2010 67

12/02/2010

68

12/02/2010

69

12/02/2010

70

12/02/2010

71

BODY WALL DEFECTS

Cleft sternum Cantrell pentalogy Omphalocele Gastroschisis Bladder exstrophy Cloacal exstrophy

12/02/2010

72

CLEFT STERNUMVentral body wall defect Lack of fusion of the bilateral bars of mesoderm Heart protudes through a sternal defect Absence of the lower third of the sternum Ectopia cordis12/02/2010 73

CANTRELL PENTALOGYECTOPIA CORDIS OMPHALOCELE

CLEFT STERNUM CON ENITAL HEART DEFECTS DIAPHRA MATIC HERNIA

12/02/2010

74

ECTOPIA CORDIS12/02/2010

CLEFT STERNUM75

12/02/2010

76

OMPHALOCELE

12/02/2010

77

GASTROSCHISIS

12/02/2010

78

CONGENITAL DIAPHRAGMATIC HERNIA

12/02/2010

79

12/02/2010

80

A: HERNIATION OF LIVER

B: HERNIATION OF STOMACH & BOWEL12/02/2010

C: CHEST RADIOGRAPH 81

12/02/2010

82

PARASTERNAL HERNIASmall part of muscular diaphragm fails to develop. Hernia may remain undiscovered until the child is several years old. A small peritoneal sac containing intestinal loops may enter the chest between the sternal & costal portions of the diaphragm.

12/02/2010

83

ESOPHAGEAL HERNIACongenital shortness of the esophagus Upper portion of the stomach retained into the thorax Stomach is constricted at the level of the diaphragm12/02/2010 84

12/02/2010

85

12/02/2010

86

REFERENCES:Developmental Anatomy, A Textbook and Laboratory Manual of Embryology By LESLIE BRAINERD AREY, Revised 7th Edition LANGMANS Embryology 10th Edition, By T.W.SADLER The Developing Human, Clinically Oriented Embryology by KEITH L. MOORE, 8th Edition Google Search for Images12/02/2010 87

12/02/2010

88