MILESTONES OF FETAL DEVELOPMENT Flashcards
starts on day 15 and continues until approximately the 8th week
embryonic stage
embryonic stage:
- embryonic disk becomes elongated & pear shaped, with a broad cephalic end & narrow caudal end
- Ectoderm has formed a long cylindrical tube for brain & spinal cord development
3 weeks
embryonic stage:
- GIT from the endoderm, appears as tubelike structure
- most advanced organ is the heart
3 weeks
embryonic stage:
days 21-32 ___ (a series of mesodermal blocks) form on either side of the embryo’s midline
somites
embryonic stage:
The ___ that form the spinal column will develop from these somites
vertebrae
embryonic stage:
- Prior to 28 days, arm & leg buds are not visible, but the tail bud is present.
- The pharyngeal arches – which will form the lower jaw, hyoid bone, & larynx – develop at this time
4-5 weeks
embryonic stage:
- The pharyngeal pouches appear now; these pouches will form the eustachian tube & cavity of the middle ear, the tonsils, & the parathyroid & thymus glands
- The primordial of the ear & eye are also present
4-5 weeks
embryonic stage:
by the end of ___ days, the tubular heart is beating at a regular rhythm & pushing its own primitive blood cells through the main blood vessels
28 days
embryonic stage:
During the ___ week, the optic cups & lens vessels of the eye form & the nasal pits develop
5th week
embryonic stage:
- Partitioning in the heart occurs with the dividing of the atrium
- Embryo has marked C-shaped body, accentuated by the rudimentary tail & the large head folded over a protuberant trunk
4-5 weeks
embryonic stage:
By day ___, the arm & leg buds are well developed, with paddle-shaped hand & foot plates. The heart, circulatory system, & brain show the most advanced development
35
embryonic stage:
Brain has differentiated into five areas, & 10 pair of cranial nerves are recognizable
4-5 weeks
embryonic stage:
- Head structures are more highly developed
- Trunk is straighter than in earlier stages
- Upper & lower jaws are recognizable
6 weeks
embryonic stage:
- External nares are well formed
- Trachea has developed & its caudal end is bifurcated for beginning lung formation
- Upper lip has formed
6 weeks
embryonic stage:
- Palate is developing
- Ears are developing rapidly
6 weeks
embryonic stage:
- Arms have begun to extend ventrally across the chest, & both arms & legs have digits, although they may still be webbed
- There is a slight elbow bend in the arms, which are more advanced in development than the legs
6 weeks
embryonic stage:
- Beginning at this stage, the prominent tail will recede
- Heart now has most of its definitive characteristics, & fetal circulation begins to be established
- Liver starts to produce blood cells
6 weeks
embryonic stage:
- Head of the embryo is rounder & nearly erect
- Eyes have shifted & are closer together
- Eyelids are beginning to form
7 weeks
embryonic stage:
Prior to this time the rectal & urogenital passages formed one tube that ended in a blind pouch; they now separate into two tubular structures
7 weeks
embryonic stage:
Intestines enter the extraembryonic coelom in the area of the umbilical cord (called umbilical herniated). At this point the beginnings of all essential external & internal structures are present
7 weeks
embryonic stage:
- Approximately 3 cm (1.2 in) long C-R
- Clearly resembles a human being
- Facial features continue to develop
8 weeks
embryonic stage:
- Eyelids begin to fuse
- Auricles of the external ears begin to assume final shape, but are still set low
- External genitals appear, but sex not clearly identifiable
8 weeks
embryonic stage:
- Rectal passage opens with the perforation of the anal membrane
- Circulatory system through the umbilical cord is well established
8 weeks
embryonic stage:
- Long bones are beginning to form
- Large muscles are now capable of contracting
8 weeks
fetal stage:
At end of ___ weeks, fetus reaches a C-R length of 5 cm (2 in) & weighs about 14 grams
9 weeks
fetal stage:
- Head is large & comprises almost half of the fetus’ entire size
- Face is well formed, with the nose protruding, the chin small & receding, & the ear acquiring a more adult shape
9-12 weeks
fetal stage:
At ___ weeks, the fetus reaches 7 to 8 cm C-R & weighs about 45 g (1.6 oz).
12 weeks
fetal stage:
Eyelids close at about ___ week & will not reopen until about the ___ week
10th,
28th
fetal stage:
- Some reflex movement of the lips suggestive of the sucking reflex has been observed at 3 months.
- Tooth buds now appear
- Limbs are long & slender, with well-formed digits.
9-12 weeks
fetal stage:
- Fetus can curl fingers toward the palm & begins to make a tiny fist
- Legs are still shorter & less developed than the arms
- Urogenital tract completes its development
9-12 weeks
fetal stage:
- Well-differentiated genitals appear
- Kidneys begin to produce urine
- Spontaneous movements of the fetus now occur
9-12 weeks
FHR can be ascertained by electronic devices between ___weeks.
8-12 weeks
fetal stage:
- A period of rapid growth
- Lanugo, or fine hair, begins to develop, especially on the head.
- Skin is so transparent
13-16 weeks
At ___ weeks, fetus weighs 55 to 120 g & is about 10 to 17 cm in C-R length
13 weeks
fetal stage:
- More muscle tissue & body skeleton have developed & hold the fetus more erect
- Active movements are present
- Fetus stretches & exercises arms & legs: makes sucking motions, swallows amniotic fluid, & produces meconium in the intestinal tract
13-16 weeks
By the beginning of week ___, skeletal ossification is clearly identifiable
16
fetal stage:
- Fetus doubles its C-R length & now measures 25 cm long
- Fetal weight is 223 g
- Lanugo covers the entire body & is especially prominent on the shoulders
20 weeks
fetal stage:
- Subcutaneous deposits of brown fat, which has rich blood supply, make the skin less transparent
- Nipples now appear over the mammary glands
- Head is covered with fine, woolly hair, & the eyebrows & eyelashes are beginning to form
20 weeks
fetal stage:
- Nails are present on both fingers & toes
- Muscles are well developed, & fetus is active
- Quickening is felt
- Fetal heartbeat audible through a fetoscope
20 weeks
fetal stage:
- The fetus reaches a crown-to-heel (C-H) length of 28 to 36 cm
- Weighs about 550 to 600 g.
- Hair on the head is growing long, & eyebrows & eyelashes have formed
24 weeks
fetal stage:
- Eye is structurally complete & will soon open
- Fetus has a reflex hand grip (grasp reflex) & by the end of 6 months has startle reflex
- Skin covering the body is reddish & wrinkled, with little subcutaneous fat
24 weeks
fetal stage:
- Skin on hands & feet have thickened, with skin ridges on palms & soles forming distinct foot – & fingerprints
- Skin over entire body is covered with vernix caseosa
- Alveoli in the lungs just beginning to form
24 weeks
fetal stage:
At ___ months, fetal skin is still red, wrinkled,& covered with vernix caseosa
6 months
fetal stage:
- During this time, brain is developing rapidly, & the NS is complete enough to provide some degree of regulation of body functions
- Eyelids open & close under neural control
- In the male fetus, testes begin to descend into the scrotal sac
25-28 weeks
fetal stage:
- Respiratory & circulatory systems have developed though lungs still physiologically immature
- Fetus is about 35 to 38 cm (14 to 15 in) long C-H & weighs 1200 to 1250 g (2 lbs, 10.5 oz to 2 lbs, 12 oz).
25-28 weeks
fetal stage:
At ___ weeks, pupillary light reflex is present
30 weeks
fetal stage:
Fetus in ___ weeks is gaining weight from an increase in body muscle & fat & weighs about 1600 g, with a C-H length of about 38 to 43 cm (15 to 17 in)
32 weeks
fetal stage:
- CNS has matured enough to direct rhythmic breathing movements & partially control body temp. though lungs are not yet fully mature
- Bones are fully developed but soft & flexible
29-32 weeks
fetal stage:
- Fetus begins storing iron, calcium, & phosphorus
- In males, the testicles may be located in the scrotal sac but often still high in the inguinal canals
29-32 weeks
fetal stage:
- Fetus begins to get plump, & less wrinkled skin covers the deposits of subcutaneous fat
- Lanugo begins to disappear
- Nails reach the edge of fingertips
35-36 weeks
fetal stage:
By ___ weeks of age, fetus has a firm grasp & exhibits spontaneous orientation to light
35 weeks
fetal stage:
By ___ weeks of age, weight is usually 1,800 to 2,700 g (5 to 6 lb), & C-H length is about 42 to 48 cm.
36 weeks
fetal stage:
- considered full term
- C-H length varies from 48 to 52 cm (19 to 21 in
- Weight at term is about 3000 to 3600 g (6 lb, 10 oz to 7 lb, 15 oz)
38-40 weeks
fetal stage:
- Skin is pink & has a smooth, polished look
- The only lanugo left is on the upper arms & shoulders
- Hair on the head is no longer woolly but is coarse & about 1 in long
- Vernix caseosa is present
38-40 weeks
fetal stage:
- Body & extremities are plump, with good skin turgor, & fingernails extend beyond the fingertips
- Chest is prominent but still a smaller than the head, & mammary glands protrude in both sexes
38-40 weeks
fetal stage:
- In males, the testes are in the scrotum or palpable in the inguinal canals.
- As the fetus enlarges, amniotic fluid diminishes to about 500 mL or less, & the fetal body mass fills the uterine cavity
- Fetus assumes what is called its position of comfort, or lie
38-40 weeks
