Fetal Skull Anatomy PDF

THE FETAL SKULL  THE FETAL SKULL It contains the delicate brain which is subject to pressure as the head passes through the pelvis. OSSIFICATION The bones of the fetal head originate in two different ways. One from membranes and the other from cartilage. T...

THE FETAL SKULL  THE FETAL SKULL It contains the delicate brain which is subject to pressure as the head passes through the pelvis. OSSIFICATION The bones of the fetal head originate in two different ways. One from membranes and the other from cartilage. The face is laid down in cartilage and almost completely ossified at birth, fused together and becomes firm.  BONES OF THE VAULT They are laid down in membranes much flatter and more pliable. Ossification centres on each bone appears as a boss or protuberance. Bones ossified from centre outwards. Process is not complete at birth. The incomplete areas are left as gaps known as sutures and fontanelles. THE FETAL SKULL  BONES OF THE VAULT There are five main bones. 1.ONE OCCIPITAL BONE It forms the back of head. Part of it forms the base of the skull. It contains the foramen magnum which protects the spinal cord. Ossification centre is called the occipital protuberance. 2.TWO PARIETAL BONES It lie on each side of the skull. Ossification centre of each is called parietal eminence.  3. TWO FRONTAL BONES They form the fore head or sinciput. At the centre of each is frontal boss or eminence. The bones fused together into one by age 8 years TEMPERAL BONES Part of these bones form the vault but they are not of most significance. SUTURES Sutures are cranial joints and are formed where two bones adjoin.  TYPES OF SUTURES THE LAMBDIODAL SUTURE - this separates the occipital bones from the two parietal bones. THE SAGITTAL SUTURE - lies between the parietal bones. THE CORONAL SUTURE this separates the frontal bones from the parietal bones, passing from one temple to the other. THE FRONTAL SUTURE - it runs between the two halves of the frontal bones. THE FETAL SKULL  FONTANELLES This is where two or more sutures meet. TYPES OF FONTANELLES POSTERIOR FONTANELLE OR LAMBDA It is situated at the junction of the lambdoidal and sagittal sutures. It is small and triangular in shape. Normally close up by 6 weeks of age. Can be recognised vaginally because suture lives each of the three angles. FONTANELLES/SUTURES  2.THE ANTERIOR FONTANELLE OR BREGMA It is situated at the junction of the sagittal, coronal and frontal sutures. It is broad. Kite shaped. It closes completely by 18months of age. It measures 3-4cm long and 1.5 -2cm wide. Pulsations of cerebral vessels can be felt through it. It can be recognised vaginally because a suture leaves from each of the corners.  REGIONS AND LANDMARKS OF THE FETAL SKULL The skull is divided into three areas. 1.Face 2. Vault 3. Base FACE It is composed of 14 small bones firmly united. THE VAULT Is a large, thin, dome shaped bones which is pliable at birth. NB It allows the skull to alter in shape during birth.  THE BASE Bones are firmly united to protect the vital centres in the medulla. REGIONS OF THE SKULL 1. THE OCCIPUT It lies between the foramen magnum and the posterior fontanelle The part below the occipital protuberance is known as suboccipital region. The protuberance is seen as a prominent point.  2. THE VERTEX It is bounded by posterior fontanelle. The two parietal eminences and anterior fontanelle. About 95% of babies born with head first present by the vertex. 3. THE SINSIPUT OR BROW It extends from the anterior fontanelle and the coronal suture to the orbital ridges.  4. THE FACE Small in new born. It extends from the orbital ridges and root of the nose to the junction of chin and neck. The point between the eyebrows is known as GLABELLA. Chin is the mentum which is an important landmark.  DIAMETERS OF THE FETAL SKULL The measurements of the skull are important because the midwife needs a practical understanding of the relationship between the fetal head and the mothers pelvis. The diameters can be grouped into transverse and anteroposterior.  TRANSVERSE DIAMETER There are two transverse diameters. 1.BIPARIETAL DIAMETER The diameters between the two parietal eminences. This is 9.5 cm. 2. BITEMPORAL DIAMETERS The diameter between the furthest points of the coronal suture at the temples. It is 8.2 cm. IMAGE ANTEROPOSTERIOR /LONGITUDINAL DIAMETERS Suboccipitobregmatic (SOB) -It is 9.5cm.measured below the occipital protruberance to the center of the anterior fontanelle or bregma. Suboccipitofrontal (SOF) – It is 10cm.measured below the occipital protruberance to the centre of the frontal suture. Occipitofrontal(OF) - It is11.5cm.its from the occipital protruberance to the glabella. DIAMETERS DIAMETERS ANTEROPOSTERIOR /LONGITUDINAL DIAMETERS CONT’D Occipitofrontal (OF) - It is11.5cm.its from the occipital protruberance to the glabella. Mentovertical (MV) - It is 13.5cm.measured from the point of the chin to the highest point on the vertex Submentovertical(SMV) - It is 11.5cm.Its from the point where the chin joints the neck to the highest point on the vertex. ANTEROPOSTERIOR /LONGITUDINAL DIAMETERS CONT’D Submentobregmatic (SMB) - It is 9.5cm. its from the point where the chin joints the neck to the centre of the bregma. NB – The most favourable diameter during labour is the Suboccipitobregmatic (SOB) and the biparietal diameters since they all have the same diameter of 9.5cm. It is the most favourable shape in dilating the cervix. This is called VERTEX PRESENTATION. THANK YOU THE END