Fetal Skull - 2020/2021 Past Paper PDF

MATERNAL AND CHILD HEALTH NURSING 3080 course code: NSG 403 Session: 2020/2021 CREDIT: 6 UNITS LECTURER R.A OYEKALE DEPARTMENT OF NURSING, FACULTY OF CLINICAL SCIENCES  TOPIC: FETAL SKULL  The fetal skull Fetal skull is...

MATERNAL AND CHILD HEALTH NURSING 3080 course code: NSG 403 Session: 2020/2021 CREDIT: 6 UNITS LECTURER R.A OYEKALE DEPARTMENT OF NURSING, FACULTY OF CLINICAL SCIENCES  TOPIC: FETAL SKULL  The fetal skull Fetal skull is the most important part of the fetus because it is the most common presenting part. It contains the delicate brain which may be subjected to great pressure as the head passes through the birth canal. It is the largest and least compressible and once born, generally ensures smooth delivery of the body. An understanding of the landmarks and measurements of the fetal skull enables the midwife to recognise normal presentation and positions and to facilitate birth with the least possible trauma to mother and baby.  The fetal skull Ossification: Bones of the fetal head originate in two different ways. Face is laid down in cartilage and almost completely ossified at birth with the bones being fused together The bones of the vault are laid down in membrane and are much flatter and more pliable. They ossified from the centre outwards and this processvis incomplete at birth leaving small gaps which forms the sutures and fontanelles. The ossified centre on each bone appears as a boss or protuberance.  The fetal skull BONES OF THE VAULT There are five main bones in the vault of the fetal skull: The occipital bone: This lies at the back of the head and forms the region of the occiput. Part of it forms the base of the skull as it contains the foramen magnum which protect the spinal cord as it leaves the skull. The occipital protuberance is at the centre of the occiput Two parietal bones: These lies on either sides of the skull. The ossification centre of each is called the parietal eminence. DIAGRAM SHOWING BONES, SUTURES AND FONTANELLES  REGIONS AND LANDMARKS ON FETAL SKULL The skull is divided into the vault, the base and the face Vault is the large dome-shaped part above an imaginary line drawn between the orbital ridges and the nape of the neck. The base comprised of bones that are firmly united to protect the vital centres in the medulla The face is composed of 14 bones which  REGIONS AND LANDMARKS ON FETAL SKULL The region of the skull are described as follows: Vertex: It is a quadrangular area bounded on one side by the bregma and coronal sutures, behind by the lambda and lambdoidal sutures and literally by lines passing through 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.  REGIONS AND LANDMARKS ON FETAL SKULL Face: It is an area bounded on one side by root of the nose and supraorbital 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 The occiput : Is limited to the occipital bone.  SUTURES Flat bones of the vault are united together by non-ossified membranes attached to the margins of the bones. These are called sutures and fontanelles. There are four major sutures on the fetal skull: Sagittal or longitudinal suture: This lies between two parietal bones The coronal sutures: Run between parietal and fontal bones on either side The frontal suture: Lies between two frontal bones The lambdoidal sutures: separate the occipital bone and the two parietal bone  IMPORTANCE OF SUTURES It permits gliding movement of one bone over the other during moulding of the head, a phenomenon of significance while the head passes through the pelvis during labour. Digital palpation of sagittal suture during internal examination in labour gives an idea of the manner of engagement of the head (synclitism or asynclitism) degree of internal rotation of the head and degree of moulding of the head.  FONTANELLES The wide gap in the suture line is called fontanelle. Of the many fontanelle (6 in numbers), two are of obstetric significance and they are: Anterior fontanelle or bregma Posterior fontanelle or lambda Anterior fontanelle It is formed by joining of these four sutures in the mid plane: Anteriorly, frontal suture Posteriorly, sagittal suture On either side, coronal suture  FONTANELLES (Anterior) CONTD The shape is like a diamond. It anterior- posterior and transverse diameters measure approx. 3cm each. The floor is formed by a membrane and it becomes ossified 18mths after birth. It becomes pathological to ossify even after 24mths. Importance Its palpation through internal VE examination donates the degree of flexion of the head It facilitates moulding of the head. As remains membranous long after birth, it helps to accommodate the marked brain growth (the brain becoming almost double its size during the first year of life)  FONTANELLE Palpation of the floor reflects intra-cranial status (depressed in dehydration elevated in raised intracranial tension) FONTANELLE(Posterior) It is formed by junction of three suture lines i.e: Sagittal suture anteriorly Lambdoidal suture on either side It is triangular in shape and measures about 1.2X 1.2cm. It donates the position of the head in relation to maternal pelvis’  DIAMETERS OF THE SKULL The engaging diameter of the fetal skull depends on the degree of flexion or extension present ATTITUDE: This is the degree of flexion of extension of the fetal neck during delivery. PRESENTATION: This is the part of the fetus that lies at the pelvic brim or in the lower pole of the uterus. DIAMETERS OF THE SKULL( anteroposterior diameters) S/N DIAMETERS ATTITUDE PRESENTATION 1. Suboccipitobregmatic(9.5cm): Extends Complete flexion Vertex from the nape of the neck to the center of the bregma. 2. Subboccipitofrontal(10cm): Extends from Incomplete flexion Vertex the nape of the neck to the anterior end of the anterior fontanelle or center of the sincipul 3. Occipitofrontal(11.5cm): Extends from the Marked deflexion Vertex occipital eminence to the root of the nose(glabella) 4. Mentovertical(3.5cm): Extends from the Partial extension Brow midpoint of the chin to the highest point on the sagittal suture 5. Submentovertical(11.5cm): Extends from Incomplete extension Face junction of floor of the mouth and neck to the highest point on the sagittal suture 6. Submentobregmatic(9.5cm): Extends from Complete extension Face junction of floor of the mouth and neck to the center of the bregma  DIAMETERS OF THE SKULL The transverse diameters which are concerned with the mechanism of labour are: Biparietal diameter(9.5cm): It extends between two parietal eminences. Whatever may be the position of the head, this diameter nearly always engages. Bitemporal diameter(8.2cm): It is the distance between the anteroinferior ends of the coronal suture between two further points of the coronal suture at the temples NOTE: Moulding this is the term applied to the change in shape of the fetal head that takes place during its passage through the birth canal.  Moulding Alteration in shape is possible because the bones of the skull allow a slight degree of bending and the skull bones are able to override at the sutures. This overriding allows reduction in the presenting diameters. DIAGRAM OF FETAL SKULL