WEEK 14 (Foetus & Placenta) Flashcards
(41 cards)
Describe the foetal period
- Beginning of Week 9 to birth
- Characterised by maturation of tissues and organs and rapid growth of the body
What is the length of the foetus indicated by?
CROWN-RUMP LENGTH (CRL) or CROWN-HEEL LENGTH (CHL)
What advances happen on the third month?
- Eyes move to ventral aspect of face & ears move to the side of head
- Limbs reach their relative length in comparison with the rest of body (lower limbs little shorter + less well developed)
- External genitalia develop -> SEX OF FOETUS DETERMINED
What advances happen on the fourth and fifth months?
- CRL is around 15cm (half the total length of the newborn)
- Weight is less than 500g
- Foetus is covered with fine hair called LANUGO HAIR
- Eyebrows and head hair are visible
During which month can movements of the foetus be felt by the mother?
Fifth month
What advances happen on the sixth month?
- Foetus weight increases considerably
- Skin of foetus is reddish and has a wrinkled appearance due to lack of underlying connective tissue
- Respiratory system and CNS have not differentiated sufficiently
What is the length of the foetus indicated by?
CROWN-RUMP LENGTH (CRL) or CROWN-HEEL LENGTH (CHL)
How long is a normal pregnancy?
280 days (40 weeks) after the last normal menstrual period OR 266 days (38 weeks) after fertilisation
By 6.5 to 7 months, what are the chances of survival?
90%
What advances happen during the last 2 months?
- Skin is covered by a whitish, fatty substance composed of secretory products from SEBACEOUS GLANDS
- Sexual characteristics are pronounced
What are the statistics of a normal foetus during the time of birth?
- 3-3.4kg
- CRL = 36cm
- CHL = 50cm
What is the placenta?
The organ that facilitates nutrient and gas exchange between maternal and foetal compartments
What is the foetal component and the maternal component derived from?
- Foetal component = Trophoblast and extra embryonic mesoderm
- Maternal component = Uterine endometrium
Which components make up the placenta?
- CHORION FRONDOSUM (foetal portion)
- DECIDUA BASALIS (maternal portion)
What is the only portion of the chorion participating in the exchange process?
Chorion frondosum
Describe the Full-term placenta
- Divided into a number of compartments (COTYLEDONS)
- Placenta enlarges as foetus grows
- 15-25cm, 3cm thick & weighs 500-600g
- Foetal surface of the placenta is covered entirely by CHORIONIC PLATE
What converges to form the Umbilical cord?
- Large arteries
- Large veins
- Chorionic vessels
Describe the circulation of the Placenta
COTYLEDONS receive blood through SPIRAL ARTERIES that pierce the DECIDUAL PLATE and enter the INTERVILLOUS SPACES -> Pressure in the arteries force blood deep into the INTERVILLOUS SPACES -> As pressure decreases, blood flows back from the CHORIONIC PLATE towards the DECIDUA where it enters the ENDOMETRIAL VEINS
What are the functions of the placenta?
- Metabolism
- Transport
- Endocrine secretion
- Protection
- Excretion
Describe foetal immunity
Immunoglobins consist almost entirely of MATERNAL IMMUNOGLOBIN G (IgG) which is transported to the foetus at 14 weeks -> Foetus gains passive immunity -> Newborns begin to produce their own gig but adult levels are not attained until 3 years old
What is attachment of the umbilical cord to the foetal membranes called?
Velamentous insertion of the cord
What can excessively long and short umbilical cords cause?
SHORT = Premature separation of the placenta from the wall of the uterus during delivery
LONG = Tendency to prolapse and/or coil around the foetus
Why is prompt recognition of the prolapse of the umbilical cord important?
The cord may be compressed between the presenting body part of the foetus and the mother’s bony pelvis -> Foetal HYPOXIA or ANOXIA -> If the deficiency of oxygen is more than 5 minutes the neonate’s brain may be damaged
Describe the structure of the umbilical cord
Two arteries and one large vein which are surrounded by mucoid connective tissue (Wharton jelly)
