Foetal Development - Answers

Arlo Guthrie — Tue, 21 Apr 2009 12:00:30 GMT

Current Revision posted to Revision Guide For Student Nurses - Part 2 by Arlo Guthrie on 4/21/2009 12:00:30 PM

ANSWERS

Give 2 names by which the uterine tube might also be known.
- Fallopian tube.
- Oviduct.
What is an oocyte?
An immature egg cell or ovum in the ovary.
What does the double protective layer that surrounds the ovum following its release from the ovary consist of?
- Zona pellucida - the glycoprotein inner layer.
- Corona radiata - the outer layer comprising follicular cells.
Where does fertilisation take place?
The Fallopian tube.
What is the fertilisation reaction?
This occurs once the first sperm has penetrated the zona pellucida, and prevents any other spermatozoa from entering the ovum.
What is a zygote?
The fertilised ovum.
When does the zygote become a morula?
Once the cells have divided to form a solid ball of cells.
What is the mass towards one end of the morula known as?
The inner cell mass.
What are the cells lining the cavity of the morula known as?
The trophoblast.
What are the 3 germ cell layers and what parts of the neonate's body will the eventually form?
- Ectoderm - skin and nervous system.
- Mesoderm - musculo-skeletal system and internal organs.
- Endoderm - gastro-intestinal tract and visceral structures.
When and where does implantation take place?
11-16 days in the queen, and 14-20 days after ovulation in the bitch. Implantation occurs at the wall of the uterus.
Name the 4 extra-embryonic membranes and their functions.
- Yolk sac - primitive gut tube.
- Chorion - the outer membrane of the embryo.
- Amnion - the inner membrane of the embryo.
- Allantois - removes urine from the foetal bladder.
Describe the formation of the water bag.
The fusion of the chorion and allantois to form the chorioallantois (the outer membrane).
Describe the formation of the slime bag.
The fusion of the allantois and the amnion to form the allantoamnion (the inner membrane).
What nutritional source does the marginal haematoma provide?
Iron.
At parturition, the marginal haematoma results in a vulval discharge - what colour is this in bitches and in queens?
- Bitches - green.
- Queens - brown.
How is the foetal circulation different to that of a mammal after birth?
- A single umbilical vein brings blood from the foetus to the placenta.
- 2 Umbilical arteries carry blood back from the placenta.
- The lungs are collapsed and oxygen is provided via the umbilical vein.
What is the falciform ligament?
The remains of the umbilical vein in an adult.
Describe the features present in a developing embryo by the end of week 4.
- Eyes are pigmented.
- The external ear is represented by a ridge of skin.
- The limbs are cylindrical with an indication of paw shape.
- The embryo measures approximately 20mm in length.
Describe the features present in a developing foetus by the end of week 6.
- Scrotal and vulval tissues are prominent.
- The eyelids are fused.
- The digits are widely spread with formed claws.
- Hair follicles are present.
- There is slight ossification of the skeleton.
- The foetus measures approximately 60mm in length.