fetus and newborn Flashcards
implantation
i) The blastocyst enters the uterine cavity 6 – 7 days after fertilization.
* The blastocyst consists of 2 types of cells : - inner cell mass 🡪 embryoblasts 🡪 embryo
-outer cell mass 🡪 trophoblast 🡪 placenta
ii) The B orients itself so that the T is overlying. Collection of cells surrounding
blastocyst (zona pellucida) disappears and blastocyst adheres to endometrium
(apposition).
The trophoblast continues to invade the endometrium and is
complicated by 24 – 25days of gestation. This process is called implantation.
iii) The site of implantation is usually along ant and more likely posterior upper walls
of uterus.
embryogenesis
*First TM: First week
i) Ovulation 🡪fertilization of ovum by spermatozoa in ampule of uterine tube. In order to fertilize the ovum, the sperm must undergo 2 changes:
a) Capacitation – Enzymatic changes in spermatozoa allows it to lose part of its acrosomal membrane takes place
during the journey of S through the uterine cavity and uterine tubes which makes it capable
of fertilization.
b) Acrosomal Reaction – release of enzymes and contents of acrosome
which penetrate corona radiate of oocyte.
ii) The zona reaction takes place; change of 2P in order to prevent entrance of
another sperm.
iii) In 36 hours 🡪 2 pronuclei fuse and one cell divided into 2 cells by cleavage
producing blastosomes. It continues to divide into peristaltic
activity for tube transports it to uterine cavity.
iv) By 3-4 days 🡪 a solid mass of 12-16 cells (macula).
v) Fluid accumulates between blastosomes 🡪 hollow fluid filled cavity 🡪 blastocytes turns to embryoblast (inner cells) and trophoblast (outer cells)
vi) Blastocyst implants into uterine lying.
● First TM : Second week
- After a few jours of implantation, trophoblast invades endometrium and produces 2 layers:
a) cytotrophoblast (Langerhans cells)
b) Syncytioblast – cells lose membranes, this is main producer of HCg - Embryoblast forms bilaminar disc by 24-26days of gestation with 2 germ layers:
a) Hypoblast (embryonic endoderm)
b) Epiblast (embryonic ectoderm)
● between epiblast + CT = amniotic cavity
● between hypoblast + CT = extracoelomic cavity
● First TM : 4 – 8th week - Ectoderm derivatives – organ and structures which maintain external contact.
● CNS + PNS
● Sensory epithelia of nose, ear, eye
● Skin, hair, nails
● Pituitary, mammary, sweat glands - Mesoderm:
● Supporting tissue of body from somatomes
● Muscle tissue from mytomes
● Cartilage and bone – sclerotome
● Blood tissue - dermatome
embryogenesis
*First TM: First week
i) Ovulation 🡪fertilization of ovum by spermatozoa in ampule of uterine tube. In order to fertilize the ovum, the sperm must undergo 2 changes:
a) Capacitation – Enzymatic changes in spermatozoa allows it to lose part of its acrosomal membrane takes place
during the journey of S through the uterine cavity and uterine tubes which makes it capable
of fertilization.
b) Acrosomal Reaction – release of enzymes and contents of acrosome
which penetrate corona radiate of oocyte.
ii) The zona reaction takes place; change of 2P in order to prevent entrance of
another sperm.
iii) In 36 hours 🡪 2 pronuclei fuse and one cell divided into 2 cells by cleavage
producing blastosomes. It continues to divide into peristaltic
activity for tube transports it to uterine cavity.
iv) By 3-4 days 🡪 a solid mass of 12-16 cells (macula).
v) Fluid accumulates between blastosomes 🡪 hollow fluid filled cavity 🡪 blastocytes turns to embryoblast (inner cells) and trophoblast (outer cells)
vi) Blastocyst implants into uterine lying.
● First TM : Second week
- After a few jours of implantation, trophoblast invades endometrium and produces 2 layers:
a) cytotrophoblast (Langerhans cells)
b) Syncytioblast – cells lose membranes, this is main producer of HCg - Embryoblast forms bilaminar disc by 24-26days of gestation with 2 germ layers:
a) Hypoblast (embryonic endoderm)
b) Epiblast (embryonic ectoderm)
● between epiblast + CT = amniotic cavity
● between hypoblast + CT = extracoelomic cavity
● First TM : 4 – 8th week - Ectoderm derivatives – organ and structures which maintain external contact.
● CNS + PNS
● Sensory epithelia of nose, ear, eye
● Skin, hair, nails
● Pituitary, mammary, sweat glands - Mesoderm:
● Supporting tissue of body from somatomes
● Muscle tissue from mytomes
● Cartilage and bone – sclerotome
● Blood tissue - dermatome
fetus development
Fetal period begins after 8th week following conception & ends in delivery.
Weeks 8-12 post conception External genitalia develop
(30-60mm embryo)
Weeks 20 Skin is covered with lanugo.
Vernix caseosa present
Weeks 28 Testes descend to internal inguinal
ring
Baby is viable
Weeks 36 One testicle usually descend into
scrotum
Lanugo tends to disappear
Weeks 40 Both testicles descend into scrotum
Nails project beyond finger tips
Closure of posterior frontanelle
characteristic of premature infant
● weight is 2500gm or less
● length is less than 44cm
● head & abdomen is relatively large
● skull bones are soft, with wide sutures & posterior fontanelle
● head circumference disproportional to chest (normally, head circumference is greater than chest by 1.5cm)
● pinnae of ears are soft & flat
● eyes are kept closed
● skin is thin, red & shiny (lack of suncutaneous fat)
● skin covered by lanugo & vernix caseosa
● poor muscle tone
● plantar creases are not visible before 34 weeks
● testicles undescended, labia minora are exposed because labia majora are not in contact
● nails not grown right up to finger tips
