Category: Diagram of the fetal skull

The ultimate transformation of a fertilized blob of genetically directed, chemically driven cells into the very person reading this--you--is an amazing process. It all starts off, of course, with the eggs your mother was born with. With fertilization, as mentioned above, the genetics direct and the chemicals drive the cell to split over and over according to a certain architecture. Eventually there are arms and legs and eyes, a stomach, liver, and everything else, hopefully where they all belong.

Of course, one structure, the brain, makes us what we are on the food chain. The superior brain of Homo sapienswith the help of an opposable thumb, has allowed us to dominate and run the world. Whether our brains are superior enough to do that well is a whole other topic!

The brain of the developing fetus changes so much over the course of gestation that it is even possible to date the stage of the pregnancy by what the brain looks like. What becomes progressively more pronounced and what makes us the thinking beings that we are is the development of neurons nerve cells. Nature has taken advantage of a property of geometry to cram in as many neurons as possible into a relatively small space--that property being surface area.

To illustrate by way of example, if you were to drive the relatively straight interstate from Los Angeles to San Francisco, you would travel a certain distance that would be recorded on your car's odometer. But if you were to take Highway 1, which follows the curves, bulges, inlets, and other miscellaneous variations of the coast, the odometer is going to record a larger number.

Now I know we're talking about a whole lot of tennis balls either way, but the theoretical number of tennis balls that could be lined up along curvy Highway 1 will dwarf the theoretical number that can be lined up along the interstate. The mathemeticians will glibly point out that this is fractal, or "non-Euclidean" geometry.

But our DNA thought of it before it was ever described in a math book, and this is the way we can cram into our brains so much more thinking and reasoning power. For the brain is not just a chunk of connected nerve cells, but bundles and tracts that interweave--up and down, over and under, in and out--presenting as the famous convolutions that is the crowning glory of our species.

If you were to look at a human brain, you'll see these convolutions, serpentine, thick tissue cylinders. If you were to measure along these structures, you would mark real estate along the bulges and into the valleys called "sulci" between them. The more convoluted the brain is and the deeper the sulci, the more surface area there is to pack extra neurons. It is during the second trimester around 20 weeks that the sulci begin developing, and the quantum leaps in further development begin after 28 weeks.

By 40 weeks, or term, the brain is a masterpiece of architecture which, because of convolutions, takes the mental abilities of a brain that should be about 10 feet wide and puts them into a package that will fit comfortably inside your typical head.It is essential for a midwife to understand the parameters and characteristics of the fetal skull because of its significance during the mechanism of labour.

Two key functions of the fetal skull are the protection of the brain, which is subjected to pressure as it descends through the birth canal during labour, and an ability to change shape, adapting to the process of labour in response to uterine contractions and the size and shape of the pelvis. By assessing the landmarks of the fetal skull, such as sutures and fontanelles, a midwife is able to diagnose the position and attitude of the fetal head in the pelvis and determine the most likely mechanism of labour and mode of delivery.

As the fetus develops in utero, the mesenchyme layer surrounding the brain starts to ossify, forming the various bones of the fetal skull. This process is called intramembranous ossification and begins between 4 to 8 weeks of gestation. The initial development of the skull occurs from this intramembranous structure, derived from neural crest cells and mesoderm.

The intramembranous structure is divided into two major components, the neurocranium, which forms the protective case of the skull, and the viscerocranium, forming the bones of the face. The neurocranium can be subdivided into the chondrocranium and the dermatocranium. The chondrocranium cartilaginous part is formed by the fusion of cartilages, and following ossification becomes the occipital, temporal, sphenoid and ethmoid bones. The dermatocranium membranous part is thought to arise from the external dermal scales developed to protect the brain.

This lies under the superficial layers of the skin, covering and protecting the dorsal section of the brain, giving rise to the parietal and frontal bones. This becomes easier to determine from approximately 8 weeks, when intramembranous ossification is more prominent. Ossification of the bones continues throughout pregnancy with individual bones ossifying from their centre. At term, the bones of the skull are thin and pliable, enabling some movement of bones to take place during labour.

The two frontal bones have usually united by term. Figure Following birth, the midwife examines the external structures of the newborn head in order to identify any unusual characteristics or abnormalities in the skull structure.

fetal skull

The fetal skull is a complex structure consisting of 29 irregular flat bones with 22 of these paired symmetrically: 8 bones form the cranium, 14 the face, and 7 the base.

It also helps inform reviews of ultrasonography and pelvimetry reports. The sutures of the fetal skull are soft fibrous tissues linking some bones of the skull. They enable moulding of the head to take place during labour and expansion of the brain as it develops during childhood. A fontanelle is a membranous, non-ossified area of the skull where three or more sutures meet.

A sinus is a naturally occurring cavity in the body. Sinuses enable blood to circulate throughout the skull and into the brain membranes. The sinuses associated with the frontal, ethmoidal, sphenoidal and maxillary bones change shape during puberty and are thought to be associated with voice tone.This is the term applied to the change in shape of the fetal head which takes place as it passes through the birth canal.

It is brought about by pressure between the fetal skull and the maternal pelvis. It results in compression of the movable bones and elongation of those which are not compressed.

diagram of the fetal skull

Moulding brings about a considerable reduction in the size of the presenting diameters while the diameter at right angle to them elongates. This is possible because of the sutures and fontanelles on the vault which allows slight degree of movement and the bones to override each other.

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In normal vertex presentation, the biperiatal diameter, sub occipito bregmatic reduce while the mentovertical lengthens. During moulding the anterior parietal bone override the posterior one, the frontal and occipital bones go under the parietal bones. The advantage of moulding is that it is a protective mechanism and prevents compression of the fetal brain, once it is not excessive, too rapid or unfavourable direction.

-- Fetal skull diameters -- Easily explained -- Hindi

The skull of a preterm baby may mould excessively while that of post mature does not mould which tend to make labour more difficult. In certain types of moulding the internal structure maybe damage given rise to oedema or haemorrhage and congestion may give rise to mild cerebral irritation.

This can lead to death or permanent brain damage. These dangerous moulding includes:.

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Excessive moulding: In cases of prolonged labour, due to cephalo pelvic disproportion, prematurity. Any baby with any of this dangerous moulding should be cot — nursed and observed for 24hrs for signs of cerebral irritation. BS Developed by Therithal info, Chennai. Toggle navigation BrainKart. Related Topics Part of the fetal skull. Measurements of the fetal skull. Importance of the fetal skull to the midwife.

diagram of the fetal skull

The scalp. The intracranial membranes and sinuses - Fetal skull. Moulding - Fetal skull. The Vulva. The Vagina. The Uterus. The Fallopian Tubes.Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising.

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diagram of the fetal skull

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Views Total views. Actions Shares. Embeds 0 No embeds. No notes for slide. Anatomy of the foetal skull 1. Four fontanelles lie at the anterior and posterior end of the temporal sutures on each side and have no obstetric importance. As it is longer than the largest diameter of the pelvic brim, the head cannot enter the pelvis.

You just clipped your first slide! Clipping is a handy way to collect important slides you want to go back to later. Now customize the name of a clipboard to store your clips.A collection of 22 bones, the skull protects the all-important brain and supports the other soft tissues of the head. As these bones grow throughout fetal and childhood development, they begin to fuse together, forming a single skull. The only bone that remains separate from the rest of the skull is the mandible, or jaw bone.

Early separation of the bones provides the fetal skull with the flexibility necessary to pass through the tight confines of the birth canal. Surrounding the brain is a region of the skull known as the cranium. In this region we have eight cranial bones:. Collectively, these bones provide a solid bony wall around the brain, with only a few openings for nerves and blood vessels. Our occipital bone contains the foramen magnum, the hole through which the spinal cord enters the skull to attach to the brain.

The occipital bone also forms the atlanto-occipital joint with the atlas the first cervical vertebra in our spine. The frontal, ethmoid, and sphenoid bones contain small hollow spaces known as paranasal sinuses. The sinuses help to reduce the weight of these bones and increase the resonance of the voice during speech, singing, and humming.

The 14 bones that support the muscles and organs of the face are collectively known as our facial bones. The facial bones consist of:.

Fetal Skull

The mandible, or jaw bone, is the only movable bone of the skull, forming the temporomandibular joint with the temporal bone. The lower teeth are rooted into the mandible while the upper teeth are rooted in the two maxillae. The maxillae also contain paranasal sinuses like the frontal, ethmoid, and sphenoid bones of the cranium. By: Tim Taylor. Last Updated: Apr 29, Anatomy Explorer Cervical Vertebrae Skull. Now please check your email to confirm your subscription. There was an error submitting your subscription.

Please try again. Email Address. All Rights Reserved. Innerbody Research does not provide medical advice, diagnosis, or treatment. You must consult your own medical professional.Select Structure. Cancel Save changes.

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Click on the structure to specify the target of your label. Fetal skull. At birth the skull is large in proportion to the other parts of the skeleton, but its facial portion is small, and equals only about one-eighth of the bulk of the cranium as compared with one-half in the adult. The frontal and parietal eminences are prominent. Ossification of the skull bones is not completed, and many of them, for example, the occipital, temporals, sphenoid, frontal, and mandible, consist of more than one piece.

Unossified regions between neighboring bones, termed fontanelles, are seen at the angles of the parietal bones; these fontanelles are six in number: two, an anterior and a posterior, are situated in the middle line, and two, an anterolateral and a posterolateral, on either side. The anterior fontanelle is the largest, and is placed at the junction of the sagittal, coronal, and frontal sutures.

The posterior fontanelle is triangular in form and is situated at the junction of the sagittal and lambdoidal sutures. The lateral fontanelles are small, irregular in shape, and correspond respectively with the sphenoidal and mastoid angles of the parietal bones. The smallness of the face at birth is mainly accounted for by the rudimentary condition of the maxillae and mandible, the non-eruption of the teeth, and the small size of the maxillary air sinuses and nasal cavities.

The skull grows rapidly from birth to the seventh year, by which time the foramen magnum and petrous parts of the temporal bones have reached their full size and the orbital cavities are only a little smaller than those of the adult. Growth is slow from the seventh year until the approach of puberty, when a second period of activity occurs. This second period of growth activity results in an increase in all directions, but it is especially marked in the frontal and facial regions, where it is associated with the development of the air sinuses.

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diagram of the fetal skull

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Fetal Anatomy--Starting at the top

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