Lectures on fetal properties and term appendages

2021-03-21 12:00 AM

The head of the fetus has two lobes, the anterior and the posterior horns. The anterior cone has a fillet shape, is located in the front. The posterior cone of the triangle, resembling the blue-poly (l) shape, is behind the landmark of the cusp.


Duration: A term fetus is a normally developing fetus in the uterus between 38 weeks and 41 weeks (average 40 weeks means 280 days).

Morphology: Anatomical structure is close to and complete as an adult. The body is divided into three parts: head, body and limbs. Term fetus weighing from 2500 grams or more. On average, Vietnamese fetuses at full term have a birthweight of 3200 ± 200g and a length of about 47-50 cm. The physiological functions of the body's organs are basically mature and can adapt to an independent life outside the mother's body after birth.

Anatomical structure

The body is divided into three parts, the head, the body and the limbs, in which the head is the solidest and most important part during childbirth because if the head passes through the subframe and passes out through the lower waist, in general, the shoulders (representative body) and butt (representing limbs) will also pass and pass easily.

The structure of the head

The fetus' head has two parts including the skull and face. The skull is again divided into two regions:

 The apical region consists of the bones of the joints and convergence of the joints that make up the lobes (the anterior and posterior tents), and the joint grooves allow the joints of this region to become semi-active. Thanks to these joint lines and the lobes, when it is difficult, these joint grooves help the bones to overlap, the reincarnation shrinks in diameter so that it is easy to fall.

The base of the skull consists of hard bones, probably not able to shrink.

The head of the fetus has two lobes, the anterior and the posterior horns. The anterior cone has a fillet shape, is located in the front. The posterior cone of the triangle, resembling the blue-poly ( l ) shape , is behind the landmark of the cusp.

The size of the fetal head is shown by the head circumference and the diameters of the head. The diameters of the head include the horizontal diameters, front and back diameters, and top and bottom diameters. Head size is very important in the spawning mechanism.

There are 5 diameters of the front and back:

Lower occipital - anterior cone: 9.5cm, which is the diameter of a good bow.

Lower occipital - forehead: 11 cm shows a medium bowed head.

Occipital - forehead: 13 cm is the diameter of the anterior pyramid.

Upper occipital - chin: 13.5 cm is the diameter of the forehead.

There is an upper - lower diameter:

Lower chin - anterior tip: 9.5 cm is the permissive diameter for the face, a type of crown with good head (maximal tilt).

There are two horizontal diameters:

Peaks: 9.5 cm.

Temples 8 cm

There are first two rounds:

Head circumference: Crossing upper occipital and chin length 34 cm.

Baby's head circumference: Crossing lower chin and anterior tapering 33 cm long.

The fetal neck makes it easy for the fetus to rotate, so that the selection of the diaphragm diameters and the easy booklet are available. The fetal neck is composed of consecutive vertebrae and can only withstand a maximum pull force of 50 kg. If pulled hard, the cervical vertebrae will dilate, causing damage to the nerves or spinal cord, resulting in death or paralysis.

Body and limbs

Shoulder diameter: 12 cm when narrowed to 9cm.

Diameter of the thigh dipole: 9 cm.

Diameter at the same time: 11 cm when narrowed to 9cm, is the diameter of the buttocks.

In general, the body and limbs of the fetus are of little importance in the delivery mechanism, because the head is downward (passed and lost), the body and limbs will also fall and pass easily.

Clinical application

When the head ring is within the normal range, the head can pass through the normal pelvis.

Only when the head is bowed well, or is tilted well (with a passing diameter of 9.5cm), the head will pass through the upper waist.

When the bipolar diameter> 9.5 cm is the big head, it is necessary to consider whether to test for the apex or double surgery.

When the diameters of the shoulder blades are large, it is easy to cause shoulder problems when the shoulder blades must use the back shoulder procedure.

When delivering, pay attention to pull the head to avoid trauma caused by trauma to the spinal cord and cervical nerve.

Physiological functions of organs

Fetal circulation

The heart has four chambers, but the atria are connected through the Botal hole.

The ductus artery is the bridge (shunt) of the aorta and pulmonary artery.

From the hypotenic artery there are two umbilical arteries that go to the placenta cake for nutrient and oxygen metabolism.

Umbilical veins from placenta cakes bring nutritious blood and oxygen to the fetus.

Nutrient-rich and oxygen-rich blood from the placenta cake, through the tube Arantius poured into the inferior vena cava, mixed with venous blood from the lower half of the body into the right atrium, through the hole Botal to the left atrium.

Blood travels from the atria to the right ventricle and then into the pulmonary artery, through the ductus arteriosus to the aorta and throughout the body.

Respiratory apparatus

The lungs are barely functional despite the breathing movements. The alveoli and bronchioles are filled with water, but when the fetus is born, the alveoli and bronchioles fluids rapidly dissipate and the surfactant (surface tension) prevents the alveoli from collapsing when have the first breath at birth.

The metabolism is done through placenta cakes.

Digestive apparatus

The digestive system is complete but not yet functional, the energy supplied to the developing fetus is absorbed through the placenta cake. In the fetal intestine there are a few cells of the gastrointestinal mucosa, bile pigments and bile salts excreted by the liver and mucus secreted by the gastrointestinal tract, creating a thick substance called checum.

Urinary apparatus

Glomeruli appeared from week 22 to week 35, when the full month has fully developed, the blood flow through the glomeruli is very little to maintain a minimum level of filtration because the placenta cake is responsible for the function of excretion. so the fetus is still alive and developing normally.

Endocrine system

Formed very early, secreting some hormones involved in the body's metabolism. Genital organs are complete but not active yet

Nerve system

The brain is complete, but the creases in the cerebral cortex indicate less developed brain cells, so the fetus can tolerate a higher level of hypoxia. The spinal cord is released so it moves freely.

Temperature control center is incomplete, so when born, it is easy to change the body temperature.

Full month subsection


Anatomical structure: The round placenta cake looks like a plate, with two sides, one side facing the uterine muscle layer and the other side looking into the amniotic chamber with the endothelium attached. placenta cake has a diameter of about 15-20 cm and is divided into about 15-20 sections, each segment is clearly separated by small grooves. placenta cake thickens from the center (about 2-3 cm) and thins out the edge of the placenta cake (0.5cm).

Histological structure:

It is a combination of the extracellular region where placentas stick up to form three layers: the bottom layer, the thick layer and the spongy layer to form the cells and the hemorrhoid.

It is a thriving mid-product region, thickening to form the placenta

There are two types of placenta thorns:

Thorns stick to the roof are responsible for hanging the placenta

Nutritional thorns are free placenta thorns located in the blood vessels. In the heart of these placenta spikes, there are blood vessels for the task of nutrition.

The surface of these placenta spikes has a layer of cytoplasm that carries out the task of metabolism and oxygen between the fetus and mother's blood.

The function of the placenta :

Performs the task of metabolism and oxygen metabolism between the fetus and maternal blood.

Endocrine function: It secretes hCG and some other steroids to participate in the maintenance and development of the fetus.

Protection function:

Prevent some pathogens, do not pass the placenta membrane to the fetus to cause disease.

Prevent some drugs with high molecular weight from causing fetal toxicity.

Gives antibodies from mother to child to fight infection.

The placenta membranes

There are three placenta membranes: the endothelium, the mesothelioma and the extracellular matrix.

Hyperplasia: Uneven development, thin outer part. The clingy placentas are strongly developed to form the bottom layer, the thick layer and the porous layer (the boundary of the placenta cake to peel off).

The mesothelioma covers and attaches tightly to the endothelium. The most thriving part becomes the placenta cake.

The endothelium is the innermost membrane that encapsulates the amniotic chamber.


The umbilical cord (also called the umbilical cord), 45-60 cm long, attaches one end to the fetal umbilical cord, and the other end clings to the placenta cake (usually in the middle), like a catheter connecting the two ends between the cake. and fetal womb.

In the umbilical cord there are two umbilical arteries (carrying blood of metabolites from the fetus to the cake) and an umbilical vein (carrying oxygen-rich blood and energy from placenta cakes) to nourish the fetus.

In the umbilical cord is Wharton jelly, clear mucus that nourishes the blood vessels of the umbilical cord.

Amniotic fluid

Normal volume ranges from 500 –1000ml.

Ingredients: 95% water, mineral salts, carbohydrates, lipids, hormones, enzymes and alkaline pH.

Amniotic fluid is produced from the urine of a fetus, through the skin, bronchi, and membranes of the mother. Amniotic fluid is also dissipated because the fetus swallows or seeps through the membranes, so the amniotic fluid is renewed every three hours.

The function of amniotic fluid is to protect the fetus from trauma and movement, so it is easy to adjust well in the uterus. When established, the head will dilate and contribute to the opening of the cervix.