Fetal Growth and Development... Final
-
Upload
red-williams -
Category
Documents
-
view
227 -
download
0
Transcript of Fetal Growth and Development... Final
-
8/13/2019 Fetal Growth and Development... Final
1/60
-
8/13/2019 Fetal Growth and Development... Final
2/60
INTRODUCTION
Understanding of the fetaldevelopment is a constructive step
towards achieving a positive
pregnancy outcome.
It provides prospective parents with
opportunity to make conscious
decisions about their health and
lifestyle.
-
8/13/2019 Fetal Growth and Development... Final
3/60
-
8/13/2019 Fetal Growth and Development... Final
4/60
OBJECTIVES
Explain the overview of fetalgrowth and development
Describe the developmental
changes that take place in the
following systems:Cardiovascular system
-
8/13/2019 Fetal Growth and Development... Final
5/60
OBJECTIVES CONTD
Respiratory system
Urogenital system
Endocrine system
Digestive system
-
8/13/2019 Fetal Growth and Development... Final
6/60
-
8/13/2019 Fetal Growth and Development... Final
7/60
OVERVIEW OF FETAL GROWTH &
DEVELOPMENT
FETUS- This name is used during the
period from the beginning of the
9thweek after fertilization to term
(end of 38thweek - 40thweek).
-
8/13/2019 Fetal Growth and Development... Final
8/60
OVERVIEW CONTD
By the beginning of the 9thfertilization, the human embryo
has developed into a recognizable
human being and most of the
body structures have commenced
development.
-
8/13/2019 Fetal Growth and Development... Final
9/60
OVERVIEW CONTD
The fetal period is mainly
concerned with differentiation and
growth of tissues and organs
which have already appeared.
-
8/13/2019 Fetal Growth and Development... Final
10/60
OVERVIEW CONTD
The fetus is less vulnerable
than the embryo, to the harmfuland deforming effects of
teratogenic agents.
-
8/13/2019 Fetal Growth and Development... Final
11/60
OVERVIEW CONTD
Tissues grow by cell proliferation,cell enlargement and accretion
(building up) of extracellular
material.
On average, the baby at termweighs 3400 grams (3.4 kg) and is
500mm long.
-
8/13/2019 Fetal Growth and Development... Final
12/60
DEVELOPMENTAL CHANGES IN THE
SYSTEMS
The cardiovascular system Is the first to function in the
embryo.
The heart and the vascular
system commences development
in the 3rdweekBy 4th week a primitive heart is
visible and is beginning to
-
8/13/2019 Fetal Growth and Development... Final
13/60
DEVELOPMENTAL CHANGES CONTD
Beating starts at around 22 daysbut can not be heard until after 16-
20 weeks.
Blood is pumped around the
vessels from the 4thweek .
-
8/13/2019 Fetal Growth and Development... Final
14/60
DEVELOPMENTAL CHANGES CONTD
The red cel l form at ion There are three phases of red blood
cell formation.
York sac period :- from 3rd13thweek
Hepatic /liver period:- from weeks 5-
36
Born marrow period:- from week 12
throughout life.
-
8/13/2019 Fetal Growth and Development... Final
15/60
DEVELOPMENTAL CHANGES CONTD
The red blood cells known as
erythrocytesproduced by the
York sac and the liver contain fetal
hemoglobin.
-
8/13/2019 Fetal Growth and Development... Final
16/60
DEVELOPMENTAL CHANGES CONTD
Fetal hemoglobin (HbF) has amuch greater affinity for oxygen
and is found in greater
concentrations (18 -20g/dl atterm).
This enhances the transfer of
oxygen across the placental site.
-
8/13/2019 Fetal Growth and Development... Final
17/60
DEVELOPMENTAL CHANGES CONTD
Fetal erythrocytes have a life spanof 90 days which is shorter than
the adult erythrocytes which is
around 120 days.
This short life span contributes toneonatal physiological jaundice.
-
8/13/2019 Fetal Growth and Development... Final
18/60
DEVELOPMENTAL CHANGES CONTD
The respiratory system Development of the respiratory
system begins in the 4thweek.
The lungs originate from the bud
growing out of the pharynx, which sub
divides to form the branching structure
of the brachial tree.
-
8/13/2019 Fetal Growth and Development... Final
19/60
DEVELOPMENTAL CHANGES CONTD
Lung development occurs onseveral levels and continues after
birth until about 8 years of age
when the full number ofbronchioles and alveoli will have
developed.
-
8/13/2019 Fetal Growth and Development... Final
20/60
DEVELOPMENTAL CHANGES CONTD
At 20 weeks development of typeII alveolar commences.
These cells are necessary for theproduction of surfactant alipoprotein that reduces the
surface tension in the alveoli andassist gaseous exchange.
-
8/13/2019 Fetal Growth and Development... Final
21/60
DEVELOPMENTAL CHANGES CONTD
The amount of surfactant increasesuntil the lungs are mature at 3034
weeks.
Babies born before 24 weeks
gestation have a reduced chance of
survival due to immaturity of the
capillary system in the lungs and the
lack of surfactant.
-
8/13/2019 Fetal Growth and Development... Final
22/60
DEVELOPMENTAL CHANGES CONTD
By 3rdmonth there is somemovement of the thorax and more
definite diaphragmatic movements
from the 6thmonth.
This does not constitute breathingas gaseous exchange is via the
placenta.
-
8/13/2019 Fetal Growth and Development... Final
23/60
DEVELOPMENTAL CHANGES CONTD
The urogenital systemThis is divided into the
urinary/renal system and
genital/reproductive system.
Both develop from theintermediate mesoderm.
-
8/13/2019 Fetal Growth and Development... Final
24/60
DEVELOPMENTAL CHANGES CONTD
The kidneys develop from the 4thweek and produce small amounts
of urine from the 9thweek.
They become more functional
around 15thweek when moreurine is produced.
-
8/13/2019 Fetal Growth and Development... Final
25/60
-
8/13/2019 Fetal Growth and Development... Final
26/60
DEVELOPMENTAL CHANGES CONTD
The sex of the fetus is determinedat fertilization. The gonadsdevelop in the 5thweek.
In the two sexes genitaldevelopment is the similar and is
referred as ind if feren t s tate o fsexual development.
-
8/13/2019 Fetal Growth and Development... Final
27/60
DEVELOPMENTAL CHANGES CONTD
Differentiation occurs from 7th
week, but female gonad
development occurs slowly and
the ovaries may not be identifiable
until the 10th
week.
-
8/13/2019 Fetal Growth and Development... Final
28/60
DEVELOPMENTAL CHANGES CONTD
External genitalia in both sexes
develop in the 9thweek, but males
and females are not
distinguishable until 12thweek.
-
8/13/2019 Fetal Growth and Development... Final
29/60
DEVELOPMENTAL CHANGES CONTD
The Endocrine systemThe adrenal glands develop from
the 6thweek, and grow to 10-20
times larger than the adult
adrenals.
Their size regresses during the
first year of life.
-
8/13/2019 Fetal Growth and Development... Final
30/60
DEVELOPMENTAL CHANGES CONTD
They produce the precursor s for
placental formation of oestriols
They influence maturation of the
liver, the lungs and the epitheliumof the digestive tract.
-
8/13/2019 Fetal Growth and Development... Final
31/60
DEVELOPMENTAL CHANGES CONTD
It is also thought that they play a
part in the initiation of labour (the
exact mechanism not fullyestablished).
-
8/13/2019 Fetal Growth and Development... Final
32/60
DEVELOPMENTAL CHANGES CONTD
The digestive systemThe primitive gut develops from
the endodemal layer in the 4th
week of life.
It starts as a straight tube and
proceeds on several levels:foregut, midgut and hindgut.
-
8/13/2019 Fetal Growth and Development... Final
33/60
DEVELOPMENTAL CHANGES CONTD
By the 5th
week, the foregut(oesophagus, stomach andduodenum) is visible.
The midgut (small intestines,caecum and appendix, ascending
colon and transverse colon)undertakes much of itsdevelopment in the 6thweek
-
8/13/2019 Fetal Growth and Development... Final
34/60
DEVELOPMENTAL CHANGES CONTD
The hindgut (rectum, and anal
canal ) completes its development
in the 7thweek.
-
8/13/2019 Fetal Growth and Development... Final
35/60
DEVELOPMENTAL CHANGES CONTD
The liver grows rapidly and from
the 5th-10thweek, fills much of the
abdominal cavity.
It is responsible for about 10% offetal weight by the 9thweek.
-
8/13/2019 Fetal Growth and Development... Final
36/60
DEVELOPMENTAL CHANGES CONTD
Around 12 weeks the digestivetract is well formed and the lumen
is patent.
Most of the digestive juices are
present before birth and act on theswallowed substances to form
meconium.
-
8/13/2019 Fetal Growth and Development... Final
37/60
DEVELOPMENTAL CHANGES CONTD
Meconium is normally retained inthe gut until after birth when it is
passed as the first stool of the
newborn.
-
8/13/2019 Fetal Growth and Development... Final
38/60
DEVELOPMENTAL CHANGES CONTD
The nervous systemThe brain begins to develop from
around day 19 and three
structures the fore brain; midbrain
and hind brain are visible.
-
8/13/2019 Fetal Growth and Development... Final
39/60
DEVELOPMENTAL CHANGES CONTD
By 5thweek, the major structures,the thalamus and the
hypothalamus are differentiated.
The neural tube is derived fromthe ectoderm.
-
8/13/2019 Fetal Growth and Development... Final
40/60
DEVELOPMENTAL CHANGES CONTD
This ectoderm folds in wards by acomplicated process to form theneural tube which is then covered
over by the skin.
This process is occasionally
incomplete, leading to a conditioncalled open neural tube defect
-
8/13/2019 Fetal Growth and Development... Final
41/60
DEVELOPMENTAL CHANGES CONTD
The development of the sensory
organs is associated with the
development of the head and
neck
which begin early in fetal life andcontinues until the cessation of
growth in the late teens.
-
8/13/2019 Fetal Growth and Development... Final
42/60
DEVELOPMENTAL CHANGES CONTD
Eyes develop from around 22days and are complete by 20
weeks but the eyelids are fused
up until the 6thmonth.
The developing eyes are sensitiveto light.
-
8/13/2019 Fetal Growth and Development... Final
43/60
DEVELOPMENTAL CHANGES CONTD
The inner ear which contains thestructures for hearing and balance
commences early in life and are
completed by 25thweek.
The fetus is able to hear externalsound.
-
8/13/2019 Fetal Growth and Development... Final
44/60
DEVELOPMENTAL CHANGES CONTD
Motor output in the form ofmovement begins around 8
weeks.
These movements are not usually
felt until around 16 weeks and areusually referred to as quickening
-
8/13/2019 Fetal Growth and Development... Final
45/60
DEVELOPMENTAL CHANGES CONTD
Integumentary, skeletal andmuscular systems
The epidermis is develops from a
single layer of ectoderm to which
other layers are added.
-
8/13/2019 Fetal Growth and Development... Final
46/60
DEVELOPMENTAL CHANGES CONTD
By the end of the first month, athin outer layer of flattened cells
covers the embryo.
Further development continues
until the sixth month.
-
8/13/2019 Fetal Growth and Development... Final
47/60
DEVELOPMENTAL CHANGES CONTD
From 18 weeks, the fetus iscovered with a white creamy
substance called vern ix caseosa.
This protects the skin from the
amniotic fluid and any frictionagainst itself.
-
8/13/2019 Fetal Growth and Development... Final
48/60
DEVELOPMENTAL CHANGES CONTD
At 20 weeks, the fetus is coveredwith a fine downy (silky, velvety)hair called lanugo, at the same
time the head hair and eye browsbegin to form.
Lanugo is shed from 36 weeksand by term there is little left.
-
8/13/2019 Fetal Growth and Development... Final
49/60
DEVELOPMENTAL CHANGES CONTD
Fingernails develop from about 10weeks but the toenails do not formuntil 18 weeks.
By term, the nails usually extendbeyond the fingertips.
Length of the nails is unreliableguide to maturity.
-
8/13/2019 Fetal Growth and Development... Final
50/60
DEVELOPMENTAL CHANGES CONTD
The skeleton first appears ascartilage
At specific periods the cartilage is
replaced is replaced by the true
bone through a process ofossification.
-
8/13/2019 Fetal Growth and Development... Final
51/60
DEVELOPMENTAL CHANGES CONTD
Nevertheless, the skull and thefacial bones develop from direct
ossification with no intermediate
cartilage stage.
Skeletal, cardiac and smoothmuscles are formed during the
fetal period and continues into
childhood. FACTORS NECESSARY FOR FETAL
-
8/13/2019 Fetal Growth and Development... Final
52/60
FACTORS NECESSARY FOR FETAL
DEVELOPMENT
Oxygen:
Necessary for all metabolic
processes
Nutrients:
Glucose: The primary source ofenergy for metabolism andgrowth
-
8/13/2019 Fetal Growth and Development... Final
53/60
FACTORS CONTD
Aminoacids,
vi tam ins ,m inerals, iron and
calc ium:
Necessary for metabolism and
growth.
-
8/13/2019 Fetal Growth and Development... Final
54/60
FACTORS CONTD
Insul in:Necessary for the metabolism of
glucose but this later is secreted
by the fetal pancreas.
FACTORS ADVERSELY AFFECTING
-
8/13/2019 Fetal Growth and Development... Final
55/60
FACTORS ADVERSELY AFFECTING
FETAL GROWTH & DEVELOPMENT
Placental insufficiency or impairedutero placenta blood flow
Maternal conditions such as
hypertension, chronic infections, andcardiac disease have detrimental
effect upon the efficiency of the
placenta to transmit nutrients fromthe mother to the fetus.
-
8/13/2019 Fetal Growth and Development... Final
56/60
FACTORS CONTD
Genetic factorsBabies born with abnormalities e.g
Downs syndrome and dwarf
syndromes are small forgestational age at birth.
-
8/13/2019 Fetal Growth and Development... Final
57/60
FACTORS CONTD
Alcohol and narcotic addiction
This causes fetal growth
retardation. Besides this, babiesborn to these mothers can also be
addicted and may have congenital
abnormalities.
-
8/13/2019 Fetal Growth and Development... Final
58/60
FACTORS CONTD
Infections and hyperpyrexia of
the mother
Many viruses such as Rubella and
HIV and other organisms can
pass through the placentalmembrane and adversely affect
fetal growth.
-
8/13/2019 Fetal Growth and Development... Final
59/60
FACTORS CONTD
Multiple pregnancy
Each placenta is usually reduced
in size and there is an increased
nutritional burden upon the mother
for each additional fetus.
-
8/13/2019 Fetal Growth and Development... Final
60/60
FACTORS CONTD
Maternal malnutrition
If the mother is lacking certain
necessary nutrients, the fetus will
also be deprived of them.