1.4: Anatomy of the Child

General Features

Much better developed at head and shoulders (big) than tail (small abdomen and buttocks)

-           abdo is pot-bellied because the liver and spleen are sizeable and pelvic organs sit high.

 

Special Features

Head

Cranial vault is huge in proportion to face, cancellous bone poorly developed.

-           growth of the alveolar bone around permanent teeth much elongates the face of the adult

Children have fontanelles where vault bones are separated at their corners

-           anterior fontanelle: fuses before 18 months

-           posterior fontanelle: fuses by 6 months

-           there is a metopic suture in the frontal bone, obliterated at 6 months.

The facial nerve is vulnerable at birth because the mastoid process is absent (until 2nd year)

External acoustic meatus is wholly cartilaginous, and the canal faces more downwards and outwards

Maxilla is short and full of developing teeth (permanents erupt at 6 years)

-           the maxillary sinus is a mere narrow slit in the child

-           the hard palate also grows backwards to accommodate the new teeth.

Mandible is in two halves initially, separated by the symphysis menti (ossifies in first year)

-           mandibular growth changes the angle of the mandibular fossa from forward to backward

-           at birth the coronoid process lies higher than the condyle, in adults ~same

 

Neck

Very short in newborns, the left brachiocephalic vein crosses the trachea above the jugular notch.

-           important in tracheotomy

Larynx and neck viscera descend slowly from a high position (reach adult stage by 7th year)

-           larynx and trachea are small-bore, thus swelling carries far more risk.

At puberty the male larynx increases rapidly, vocal cords elongate from 8-16mm in one year.

-           unless they are castrated first.

 

Thorax

Infant thorax is nearly circular; in adults lateral diameter is 3x AP diameter

-           the thymus regresses at puberty.

 

Abdomen

Liver is large and palpable

Kidneys are lobulated with little fat

Suprarenals are enormous.

The caecum balloons out in infancy (appendix thus lies posteriorly on the medial wall).

The pelvis is small and bladder lies above the symphysis even when empty.

 

Limbs

Upper limp more developed thank lower, with a pronounced grasping reflex

-           growth in arm length occurs at shoulder and wrist than the elbow

The leg occupies the fetal flexion position for 6 months or more.

-           undergoes extension and medial rotation to carry the flexors posteriorly

-           growth occurs at knee more than hip or ankle

 

Vertebrae

Until birth the column is c-shaped, concave ventrally (constriction in utero)

-           assumes normal curves as pelvis tips forward to accommodate standing.

Spinal cord extends to 3rd lumbar vertebra at birth; extents to L1/L2 in adults.