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HISTOLOGY & EMBRIOLOGY II > WEEK 14 (Foetus & Placenta) > Flashcards

WEEK 14 (Foetus & Placenta) Flashcards

1
Q

Describe the foetal period

A
  • Beginning of Week 9 to birth
  • Characterised by maturation of tissues and organs and rapid growth of the body
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2
Q

What is the length of the foetus indicated by?

A

CROWN-RUMP LENGTH (CRL) or CROWN-HEEL LENGTH (CHL)

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3
Q

What advances happen on the third month?

A
  • 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
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4
Q

What advances happen on the fourth and fifth months?

A
  • 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
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5
Q

During which month can movements of the foetus be felt by the mother?

A

Fifth month

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6
Q

What advances happen on the sixth month?

A
  • 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
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7
Q

What is the length of the foetus indicated by?

A

CROWN-RUMP LENGTH (CRL) or CROWN-HEEL LENGTH (CHL)

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7
Q

How long is a normal pregnancy?

A

280 days (40 weeks) after the last normal menstrual period OR 266 days (38 weeks) after fertilisation

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8
Q

By 6.5 to 7 months, what are the chances of survival?

A

90%

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9
Q

What advances happen during the last 2 months?

A
  • Skin is covered by a whitish, fatty substance composed of secretory products from SEBACEOUS GLANDS
  • Sexual characteristics are pronounced
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10
Q

What are the statistics of a normal foetus during the time of birth?

A
  • 3-3.4kg
  • CRL = 36cm
  • CHL = 50cm
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11
Q

What is the placenta?

A

The organ that facilitates nutrient and gas exchange between maternal and foetal compartments

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12
Q

What is the foetal component and the maternal component derived from?

A
  • Foetal component = Trophoblast and extra embryonic mesoderm
  • Maternal component = Uterine endometrium
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13
Q

Which components make up the placenta?

A
  • CHORION FRONDOSUM (foetal portion)
  • DECIDUA BASALIS (maternal portion)
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14
Q

What is the only portion of the chorion participating in the exchange process?

A

Chorion frondosum

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15
Q

Describe the Full-term placenta

A
  • 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
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16
Q

What converges to form the Umbilical cord?

A
  • Large arteries
  • Large veins
  • Chorionic vessels
17
Q

Describe the circulation of the Placenta

A

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

18
Q

What are the functions of the placenta?

A
  • Metabolism
  • Transport
  • Endocrine secretion
  • Protection
  • Excretion
19
Q

Describe foetal immunity

A

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

20
Q

What is attachment of the umbilical cord to the foetal membranes called?

A

Velamentous insertion of the cord

21
Q

What can excessively long and short umbilical cords cause?

A

SHORT = Premature separation of the placenta from the wall of the uterus during delivery

LONG = Tendency to prolapse and/or coil around the foetus

22
Q

Why is prompt recognition of the prolapse of the umbilical cord important?

A

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

23
Q

Describe the structure of the umbilical cord

A

Two arteries and one large vein which are surrounded by mucoid connective tissue (Wharton jelly)

24
Q

What’s the difference between False knots and True knots?

A

False knots = no significance

True knots = may tighten and cause foetal death resulting from anoxia

[CAUSE: Because the umbilical vessels are longer than the cord, twisting and bending of the vessels are common causing knots]

25
Q

Describe the formation of the Amniotic sac

A

The thin but tough amnion forms a fluid-filled, membranous AMNIOTIC SAC that surrounds the embryo and the foetus -> The sac contains AMNIOTIC FLUID -> As AMNION enlarges, it gradually obliterates the chorionic cavity and forms the epithelial covering of the umbilical cord

26
Q

What is amniotic fluid secreted by?

A
  • Amnion cells
  • Foetal respiratory ad gastrointestinal tracts
27
Q

Why is amniotic fluid similar to foetal tissue fluid?

A

Before KERATINISATION of the skin occurs, a major pathway for passage of water and solutes in tissue fluid from the foetus to the amniotic cavity is THROUGH THE SKIN

28
Q

Describe the circulation of amniotic fluid

A

Amniotic fluid is swallowed by the foetus and is absorbed by the foetus’ respiratory and digestive tracts -> Excess water in foetal blood is excreted by the FOETAL KIDNEYS and returned to the amniotic sac through the FOETAL URINARY TRACT

29
Q

What is the composition of Amniotic fluid?

A
  • An aqueous solution in which undissolved material is suspended
  • Half is protein
  • Other half is carbohydrates, fats, enzymes, hormones and pigments
30
Q

What is Amniocentesis and what is its importance?

A

Amniocentesis = A needle is inserted through the lower abdominal and uterine walls into the amniotic cavity. A syringe is attached and amniotic fluid is withdrawn for diagnostic purposes.

Since foetal urine enters the amniotic fluid -> Fluid removed by AMNIOCENTESIS -> Studies of cells allow for diagnosis of chromosomal abnormalities

31
Q

What do high and low levels of alpha fetoprotein usually indicate?

A

High levels = presence of a severe neural tube defect

Low levels = chromosomal aberrations

32
Q

What is the function of Amniotic fluid?

A
  • Allows symmetric external growth of foetus
  • Barrier to infection
  • Allows normal foetal lung development
  • Cushions the embryo
  • Maintains foetus’ body temperature
  • Enables foetus to move freely -> aids muscular development
  • Maintains homeostasis of fluid and electrolytes
33
Q

How does the body prepare for labor?

A
  • MYOMETRIUM thickens in the upper region of the uterus
  • Softening and thinning of the lower region and cervix
34
Q

What are the stages of labor?

A

1) Effacement (thinning and shortening) and dilation of the cervix
2) Delivery of the foetus
3) Delivery of the placenta and foetal membranes

35
Q

What is Parturition?

A

The process during which the foetus, placenta and foetal membranes are expelled from the mother’s reproductive tract

36
Q

Describe the first stage of delivery (Effacement and dilation of the cervix)

A

Produced by uterine contractions that force the amniotic sac against the cervical canal -> If membranes have ruptured, pressure will be exerted by the foetal head

37
Q

What is stage two and three of labor aided by?

A
  • Uterine contractions
  • Intra-abdominal pressure
38
Q

Which hormones are involved in birth?

A
  • OXYTOCIN
  • PROSTAGLANDINS (promote uterine contractions)
  • ESTROGENS (increase myometrial contractile activity + release of oxytocin and prostaglandins)
39
Q

Describe Oxytocin

A
  • Cause uterine smooth muscle contractions
  • Released by the NEUROHYPOPHYSIS of the pituitary gland
  • Stimulates release of prostaglandins
40
Q

What does partial spitting of the primitive node and streak result in?

A

Formation of conjoined twins

HISTOLOGY & EMBRIOLOGY II (13 decks)

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