Morphologic features of the fetal head and body

Mature fetal head structure. On the fetal head there are sutures (frontal, sagittal, coronal, lambda) and fontanels (large, small, and two lateral on each side).

The frontal suture is situated between the frontal bones, the sagit­tal suture — between the parietal bones, the coronal suture — between both frontal and both parietal bones, the lambda suture — between two parietal and the occipital bone.

The large fontanel (anterior) is located between the posterior parts of both frontal and anterior parts of both parietal bones; it is a rhomboid connective tissue plate. The small fontanel (posterior) is triangular and is located between the posterior parts of both parietal bones and the occipital one.

The large and small fontanels are joined with the sagittal suture.

The lateral fontanels are situated: anterior — between the frontal, temporal and cuneiform bones, posterior — between the temporal, pa­rietal and occipital bones. They are closed in a mature fetus.

The fetal head has the following dimensions and corresponding circumferences:

— the straight dimension {d. frontooccipitalis) is measured from the bridge of nose to the most protrudent point of occiput, makes 12 cm; the circumferencia frontooccipitalis makes 35 cm;

— the large oblique dimension (d. mentooccipitalis) is measured from the chin to the most distant point of occiput, makes 13.5 cm. The corresponding circumference makes 41 cm;

— the small oblique dimension (d. suboccipito-bregmaticus) is measured from the suboccipital fossa to the middle of large fontanel, makes 9.5 cm. The corresponding circumference makes 32 cm;

---the middle oblique dimension (d. suboccipito-frontalis) is mea­sured from the occipital fossa to the margin of the pilar part of fore­head, makes 10 cm. The corresponding circumference makes 33 cm;

---the vertical dimension (d. sublinguabregmaticus) is measured from the middle of large fontanel to the hyoid bone, makes 9.5 cm; The corresponding circumference makes 33 cm;

— the large transversal dimension (d. parietalis) is measured be­tween the most distant points of parietal protuberances, makes 9.5 cm;

— the small transversal dimension (d. parietalis) is measured be­tween the most distant points of coronal suture, makes 8 cm;

— the diameter of the pelvic area (d. interotrochanterica) makes 9.5 cm. The corresponding circumference makes 28 cm;

— the diameter of the shoulder girdle (d. biacromalis) makes 12 cm. The corresponding circumference makes 35 cm.

Mature and full-term fetus signs

Fetal maturity signs:

1. mature fetus' height is more than 47 cm;

2. mature fetus' weight is more than 2,500 g;

3. the umbilical ring is located in the middle between the uterus and the xiphoid process;

4. the skin is pink, healthy, developed. Vernix caseosa is found only in the inguinal and axillary folds;

5. the fingernails cover the ends of finger bones;

6. the hair on the head is 2 cm long;

7. the cartilages of nose and ears are tight;

8. in boys the testicles are in the scrotum; in girls the large lips of pudendum cover the clitoris and small lips of pudendum.

The fetus is considered full-term if it is born in the period from the 37^th to the 41^st week of pregnancy inclusive. Most often there is perfect coincidence between fetal maturity and its being full-term. Still, sometimes a child is born before the term being absolutely ma­ture by its development. At unfavorable conditions of intrauterine development a full-term child may have signs of immaturity.

Date: 2014-12-28; view: 1511