Physio Ch. 28.5
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55 Terms
What is oogenesis?
The production of female gametes (oocytes)
Where does oogenesis occur?
In the ovaries
When does oogenesis begin?
During embryonic development
How many primary oocytes exist at 5 months of fetal development?
About 7 million
How many primary oocytes remain at birth?
About 2 million
How many primary oocytes remain at puberty?
About 400,000
What happens to the majority of oocytes?
They degenerate through atresia
What do oogonia develop into?
Primary oocytes
What stage are primary oocytes arrested in?
Prophase I of meiosis
When does meiosis resume in females?
At puberty
What is ovulation?
Release of a secondary oocyte from the ovary
What triggers ovulation?
LH surge
When does ovulation occur after LH surge?
About 34-38 hours later
How many oocytes are typically released per cycle?
One
What are the three phases of the ovarian cycle?
Follicular phase, ovulation, luteal phase
What happens during the follicular phase?
Follicles grow and mature
Which hormone stimulates follicle development?
FSH
What hormone do developing follicles secrete?
Estrogen
What does estrogen do during this phase?
Stimulates growth of endometrium
What causes the LH surge?
High estrogen levels
What is the role of LH surge?
Triggers ovulation
What structure forms after ovulation?
Corpus luteum
What hormones does corpus luteum secrete?
Progesterone and estrogen
What is the function of progesterone?
Maintain uterine lining
What happens if fertilization does not occur?
Corpus luteum degenerates
What are the three phases of the uterine cycle?
Menstrual, proliferative, secretory
What happens during the menstrual phase?
Functional layer of endometrium is shed
How long does menstrual phase last?
About 5 days
How much blood is lost during menstruation?
35-50 mL
What stimulates the proliferative phase?
Estrogen
What happens during this phase?
Endometrium rebuilds and thickens
What hormone dominates the secretory phase?
Progesterone
What happens during this phase?
Endometrium becomes highly vascular and glandular
What is the purpose of the secretory phase?
Prepare uterus for implantation
What hormone is released from hypothalamus to start cycle?
GnRH
What does GnRH stimulate?
Release of FSH and LH from anterior pituitary
What does FSH do?
Stimulates follicle development
What does LH do?
Triggers ovulation
What happens at low estrogen levels?
Negative feedback inhibits LH and FSH
What happens at high estrogen levels?
Positive feedback triggers LH surge
What hormone inhibits FSH after ovulation?
Inhibin
What hormone dominates follicular phase?
Estrogen
What hormone dominates luteal phase?
Progesterone
What happens if progesterone levels fall?
Menstruation begins
Where does fertilization occur?
Uterine tube
What is the result of fertilization?
Formation of a zygote
What happens after fertilization?
Zygote begins dividing
What must occur for pregnancy to continue?
Implantation in uterus
What happens to corpus luteum?
It degenerates
What happens to hormone levels?
Estrogen and progesterone drop
What is triggered by hormone drop?
Menstrual phase
What is the average length of the ovarian/uterine cycle?
28 days
What is the range of cycle length?
21-35 days
When does ovulation typically occur in a 28-day cycle?
Around day 14
What determines timing of ovulation?
LH surge timing