FETAL SKULL AND FETAL CIRCULATION

FETAL SKULLFetal skull is compressible, and made

mainly of thin pliable tabular(flat) bones forming the vault.

AREAS OF SKULL VERTEX BROW FACE

VERTEX: It is a quadrangular area bounded anteriorly by the bregma and coronal suture behind by the lambda and lambdoidal sutures and laterally by lines passing thru the parietal eminences.

BROW :It is an area bounded on one side by the anterior fontanelle and coronal sutures and on the other side by the root of the nose and supra-orbital ridges of either side.

FACE: It is the area

bounded by the root of the nose and supra-orbital ridges and on the other, by the junction of the floor of the mouth with neck.

SINCIPUT: is the area lying in front of the anterior fontanelle and corresponds to the area of brow.

OCCIPUT: is the area limited to the occipital bone.

SUTURESFlat bones of the vault are united

together by the non-osssified membranes attached to the margins of the bones. These are called sutures.

THE SAGGITAL SUTURE: lies b/w two parietal bones.

THE CORONAL SUTURES :run b/w parietal and frontal bones on either sides.

Cont…

THE FRONTAL SUTURE : lies b/w two frontal bones.

THE LAMBDOIDAL SUTURES : separate the occiput bone and two parietal bones.

IMPORTANCE It permits gliding movement of one

bone over the other during moulding of the head.

Digital palpations of sagittal suture during internal examination in labour gives an idea of the manner of engagement of the head, degree of internal rotation of the head and degree of moulding of the head.

FONTANELLESWide gap in the suture line is called

fontanelle.Two obstetrical significance fontanelle are:

ANTERIOR FONTANELLE: Formed by joining four sutures in

midplane.Anteriorly frontal.Posteriorly saggital.On either side coronal suture.

Diamond like shape.

Floor is made by a membrane.

Ossified at 18mth after birth.

IMPORTANCE Its palpation thru internal

examination denotes the degree of flexion of the head.

It facilitates the moulding of the head.

It helps in accomodating the marked brain growth.

Palpation reflects intracranial status.

POSTERIOR FONTANELLE:

Formed by junction of three sutures.

Saggital suture anteriorly.

Lambdoidal suture on either side.

Triangular in shape.

Measures about 1.2 1.2cm.

Its floor is membranous but become bony at

3mth.

IMPORTANCE It denotes the position of the head in

relation to maternal pelvic.

DIAMETERS OF SKULL

DIAMETERS ATTITUDE OF THE HEAD

PRESENTATION

SUBOCCIPITO-BREGMATIC: 9.5cm extends from nape of neck to centre of bregma.

COMPLETE FLEXION VERTEX

SUBOCCIPITO-FRONTAL : 10cm extends from nape of neck to centre of sinciput.

INCOMPLETE FLEXION VERTEX

OCCIPITO-FRONTAL:11.5cm extends from the occipital eminence to the root of the nose.

MARKED DEFLEXION VERTEX

MENTO -VERTICAL:14cm extends from the mid point of chin to the highest pt. on the saggital suture.

PARTIAL EXTENSION BROW

SUBMENTO-VERTICAL: 11.5CM extends from junction of floor of mouth and neck to the highest pt. on saggital suture.

INCOMPLETE FLEXION FACE

SUBMENTO-BREGMATIC: 9.5CM extends from junction of floor of mouth and neck to centre of bregma.

COMPLETE FLEXION FACE

TRANSEVERSE DIAMETERS BIPARIETAL DIAMETER:9.5cm

extends b/w two parietal eminences.

SUPER-SUBPARIETAL:8.5cm extends from a point placed below one parietal eminence to a pt. placed above the other parietal eminence of the opposite side.

BI-TEMPORAL:8cm dist. b/w antero-inferior ends of the coronal suture.

BI-MASTOID: 7.5cm dist. b/w tips of the mastoid process.

MOULDING:

It is the alteration of the shape of the forecoming head while passing thru the resistant birth passage during labour.

IMPORTANCE: Enables head to pass more easily, thru the

birth canal. Shape of the moulding can be an useful

information about the position of head occupied in the pelvis.

Structures in fetal circulation Umbilical vein carries Oxygen &

nutrients to fetus. 2 umbilical arteries carry deoxygenate

blood and waste product from the fetus. Ductus venosus from shunts blood from

umbilical vein to inf. Vena cava, bypassing the liver and the organs of digestion.

Foramen ovale shunts blood from rt. Atrium to left atrium.

Ductus arterioses- Shunts blood from pulmonary artery to aorta bypassing lungs.

FETAL CIRCULATIONUmblical vein carry 80% oxygenated

blood from placenta. entersFetus at umblicus & run along the

falciform ligament of liver. thenBranches to left lobe of liver & receives

deoxygenated blood from portal vein.

More oxygenated blood, mixed with some portal blood, short circuits liver thru ductus venosus.

enters Inferior vena cava. ( mean co is inc. in

fetus)

Rt. Atrium of heart.

(Superior+inferior Vena cava)

25% of blood pass 75% of bl ood pass thru

Thru tricuspid valve . foraman ovale.

Into rt. Ventricle. Into lt.atrium (blood mixes with venous blood

Pul. trunk returning from lungs thru pul. vein)

(resist in pul.

Artery is high.

So main portion

Of blood) thru mitral opening

pass through ductus artriosus

lt. ventricle

to ventricular

systole

Descending aorta Blood pumped into ascending aorta and

arch of aorta and distribute to,head,

neck, brain arms and heart

by pass (lungs)

leaves the body by the

Way of

2 umbical arteres reach

Placenta (ready for recirculation)

CHANGES OF THE FETAL CIRCULATION AT BIRTH

CLOSURE OF UMBILICAL ARTERIES: Obliteration takes place about 2-3 mths. The distal parts from the lateral umbilical ligaments and the proximal parts remain open as superior vesical arteries.

CLOSURE OF UMBILICAL VEIN: The Obliteration occurs a little later than the arteries. After obliteration, the umbilical vein from the ligamentum teres and the ductus venosus become ligament venosum.

CLOSURE OF THE DUCTUS ARTERIOSUS: Functional closure of the ductus may occur soon after the establishment of pul. circulation, the anatomical obliteration takes about 1-3mths and becomes ligamentum arteriosum.

CLOSURE OF THE FORAMEN OVALE: Functional closure occurs soon after birth but anatomical closure occurs in about 1yr.

(After birth CO is 500ml/min. and heart rate varies from 120-140 /min.)

RECAPTULIZATION Posterior fontanelle is of……………..

Shape. Anterior fontanelle formed by joining

………., ……….and……….. Sutures. Occipito-frontal is ………..cm. Longest diameter is………… and of

………cm. Saggital suture lies b/w …………

bones. …………. carries Oxygen & nutrients to fetus.

BIBLIOGRAPHY

Dutta D.C. Textbook of obstetrics 6th edition central publishers.page-83-94,42-44.

www.blurtit.com/q328911. www.tripdatabase.com/doc/226448 www.purposegames.com/game/

fetal-skull-fontanelles.