Topic 23 - Development and Birth

Question 1

Learning Objectives

Answer 1

1. Describe the formation of the major organ systems and growth of the fetus.
2. Describe the process of early development, gastrulation and neurulation
3. Describe the association between germ layers and organ systems

Question 2

Menstural cycle

Answer 2

• always starts with the menses/ bleeding (4-5days)

Proliferative stage
Secretory stage

Question 3

Proliferative stage

Answer 3

• Lots of proliferation of endometrial cells
• No progesterone present to inhibit follicle growth
• When follicles develop LH and FSH levels rise
• +ve feedback loop, more follicles more FSH and LH -> more follicles
• When LH peaks, it stimulates ovulation of the oocyte to undergo meiosis 1, becoming a haploid oocyte (secondary oocyte)

Question 4

Secretory Stage

Answer 4

• Corpus luteum forms when secondary oocyte is formed after meiosis 1
• Corpus luteum secretes progesterone
• Corpus luteum thickens the endometrium lining more
• Progesterone and estrogen inhibit the hypothalamus from secreting GnRH, LH and FSH production by the anterior pituitary gland

Question 5

If fertilisatoin occurs

Answer 5

• 7-8 days after ovulation
• Endometrial lining thickens more due to corpus luteum producing progestrone
• Embryo then sits in endomedtrial lining

Question 6

Fertilisation and preimplantation embryo development

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Answer 6

• Acrosomal head of the sperm releases enzymes to allow it swim stronger and get into the oocyte via capacitation

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Question 7

Development and birth

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Answer 7

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