906
UNIT SIX
calcium and vitamin D to promote the development and ossi-
f cation oF skeletal structures (see chapter 7, p. 200); iron to
support blood cell Formation; and vitamin C For production
oF structural tissues such as cartilage and bone.
Childhood
Childhood
begins at the end oF the f rst year and ends at
puberty. During this period, growth continues at a rapid rate.
The primary teeth appear, and then secondary teeth replace
them (see chapter 17, pp. 658–659). The child develops vol-
untary muscular control and learns to walk, run, and climb.
Bladder and bowel controls are established. The child learns
to communicate eFFectively by speaking, and later, usually
learns to read, write, and reason objectively. At the same
time, the child is maturing emotionally.
PRACTICE
40
Def
ne
infancy
.
41
What developmental changes characterize inFancy?
42
Def
ne
childhood
.
43
What developmental changes characterize childhood?
Adolescence
Adolescence
is the period oF development between puberty
and adulthood. It is a time oF anatomical and physiological
changes that result in reproductively Functional individuals
(see chapter 22, pp. 846 and 857). Most oF these changes are
hormonally controlled, and they include the appearance oF
secondary sex characteristics as well as growth spurts in the
muscular and skeletal systems.
±emales usually experience these changes somewhat
earlier than males, so early in adolescence, Females may be
taller and stronger than their male peers. However, Females
attain Full growth at earlier ages, and in late adolescence, the
average male is taller and stronger than the average Female.
The periods oF rapid growth in adolescence, which usu-
ally begin between the ages oF eleven and thirteen in Females
and between thirteen and f
Fteen in males, increase demands
For certain nutrients. It is not uncommon For a teenager to
consume a huge plate oF Food, go back For more—and still
InFancy also brings the beginning oF the ability to com-
municate. The inFant learns to smile, laugh, and respond to
some sounds. By the end oF the f rst year, the inFant may be
able to say two or three words. OFten one oF a child’s f rst
words is the name oF a beloved pet.
InFancy (as well as childhood) is a period oF rapid
growth, so the inFant has particular nutritional requirements.
In addition to an energy source, the body requires proteins
to provide the amino acids necessary to Form new tissues;
Oxygenated
blood
Deoxygenated
blood
Aorta
Foramen ovale
closes and becomes
fossa ovalis
Ductus venosus
constricts and
becomes solid
ligamentum
venosum
Liver
Umbilical
vein becomes
solid
ligamentum
teres
Distal portions
of umbilical
arteries constrict
and become
medial umbilical
ligaments
Proximal portions of
umbilical arteries persist
as superior vesical arteries
Inferior vena cava
Ductus arteriosus
constricts and
becomes solid
ligamentum
arteriosum
FIGURE 23.32
Major changes occur in the newborn’s
cardiovascular system.
TABLE
23.8
|
Cardiovascular Adjustments in the Newborn
Structure
Adjustment
In the Adult
Umbilical vein
Constricts
Becomes ligamentum teres that extends From the umbilicus to the liver
Ductus venosus
Constricts
Becomes ligamentum venosum superf
cially embedded in the wall oF the liver
±oramen ovale
Closes by valvelike septum primum as blood pressure in right
atrium decreases and blood pressure in leFt atrium increases
Valve Fuses along margin oF Foramen ovale and is marked by a depression
called the Fossa ovalis
Ductus arteriosus
Constricts
Becomes ligamentum arteriosum that extends From the pulmonary trunk to
the aorta
Umbilical arteries
Distal portions constrict
Distal portions become lateral umbilical ligaments; proximal portions
Function as superior vesical arteries
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