Human Reproduction and Development Flashcards
(76 cards)
1
Q
What are primary sex organs called?
A
- gonads
2
Q
Primary sex organs (gonads) in male and female
A
- testes in males
- ovaries in females
3
Q
What do gonads produce?
A
- sex cells or gametes
- steroid hormones called sex hormones
4
Q
Accessory reproductive organs
A
- ducts, glands and external genitalia
5
Q
What do testes produce?
A
- sperm
- seminiferous tubules produce them in fact
6
Q
Location of testes
A
- within the scrotum – sac of skin and superficial fascia that hungs outside the abdominal cavity at the root of penis
7
Q
Midline that divides the scrotum
A
- septum
- provides the compartment for each testes
8
Q
Male duct system in order
A
- epididymis, ductus deferens, ejaculatory duct, urethra
9
Q
Male accessory glands
A
- paired seminal glands and a single prostate
10
Q
Spermatogenesis
A
- process in which seminiferous tubules of the testes produce male gametes called sperm or spermatozoa
11
Q
normal chromosomal number in most body cells
A
- diploid 2n
- in humans, diploid chromosomal number is 46, containing 23 pairs of chromosomes called homologous chromosomes
12
Q
chromosomes in humans
A
- 23 pairs
- homologous chromosomes or homologues
13
Q
Number of chromosomes in human gametes
A
- 23
- haploid chromosomal number
14
Q
What is hormonal control in reproductive system called?
A
- hypothalamus-pituitary-gonadal axis
15
Q
Define pregnancy
A
- events that occur from the time of fertilization (conception) until the infant is born
16
Q
Conceptus
A
Developing offspring in the womb
17
Q
Gestation period
A
- from last menstrual period until birth
- approximately 280 days
18
Q
Embryonic period
A
- from fertilization through week 8
19
Q
When is conceptus called an embryo?
A
- during embryonic period
- fertilization to week 8
20
Q
When is conceptus called a fetus?
A
- during fetal period
- from week 9 through birth
21
Q
Fetal period
A
- from week 9 to birth
22
Q
When does ovum complete meiosis II?
A
- only when sperm penetrates the oocyte and is finding its way to the nucleus
23
Q
When does fertilization occur?
A
- when sperm’s chromosomes combine with those of egg (secondary oocyte) to form a fertilized egg (zygote)
24
Q
What happens when the sperm enters the oocyte?
A
- sperm’s plasma membrane is gone
- sperm uses microtubules to locomote its nucleus towards oocyte nucleus
- meanwhile, nucleus grows bigger into a male pronucleus
- secondary oocyte completes meiosis II forming ovum nucleus and second polar body
25
Male pronucleus + female pronucleus
- mitotic spindle develops between them
- nuclei membranes rupture and chromosomes are released
26
When is the "true" moment of fertilization?
- when maternal and paternal chromosomes combine and produce diploid zygote (fertilized egg)
27
Explain "cleavage" period in embryonic development
- mitotic divisions of zygote without intervening growth to increase surface-to-volume ratio for nutrient uptake and waste disposal
28
Cleavage division 36 hours after fertilization
- first division
- 2 identical daughter cells called blastomeres
29
Cleavage division 72 divisions after fertilization
- cluster of 16 or more cells called morula
30
How many cells does the embryo have after 4 or 5 days of fertilization?
- about 100 cells that accumulate fluid within internal cavity
31
How many days does the blastocyst float in the uterine cavity?
- two to three days
32
How is the blastocyst nourished while floating in the uterine cavity?
- glycoprotein-rich uterine secretions
- steroid and nutrients like iron and fat-soluble vitamins
33
When does implantation begin?
- six to seven days after ovulation when the endometrium is properly prepared
34
What does the sperm use to approach, bind and enter the oocyte?
- acrosomal enzymes and receptors
- receptors in oocyte cause the Ca2+ levels within sperm to rise triggering acrosomal reaction
- enzymes digest holes through zona pellucida of the oocyte
35
How can polyspermy be blocked?
- entry of sperm causes oocyte cytoplasm Ca2+ to rise
- it triggers cortical reaction that hardens zona pellucida and sperm receptors are clipped off
36
How long does implantation take?
- about 5 days, usually completed 12 days after ovulation
37
How is the viability of corpus luteum maintained?
- hCG secreted by trophoblast cells
- prompts corpus luteum to continue secreting progesterone and esterogen
38
When is hCG detectable?
- one week after fertilization until end of second month
- after that, the level falls and reaches a low by 4 months
39
Placenta between 2 and 3 months
- takes over to produce estrogen and progesterone until the end of pregnancy (corpus luteum degenerates)
40
How does the embryo get nutrients before placenta?
- by digesting endometrial cells
41
Function of trophoblast cells
- secret hCG
- give embryo nutrients
- develop into placenta
42
Placentation
- formation of placenta
- cells from original inner cell mass give rise to extraembryonic mesoderm layer that lines the inner surface of trophoblast
43
What is the chorion?
- double-layered membrane formed by the trophoblast and the extra-embryonic mesoderm
- helps in the exchange of nutrients, gases, and wastes between the embryo and the mother's body.
44
What is the gastrula?
- blastocyst is being converted into 3 primary germ layers (during week 3)
- endoderm, ectoderm, mesoderm
45
What happens to inner cell mass before becoming three-layered?
- it subdivides into 2 layers
- upper epiblast and lower hypoblast
- subdivided inner cell mass is embryonic disc
46
What is the embryonic disc?
- subdivided inner cell mass before becoming three-layered
- with upper epiblast and lower hypoblast
47
What do the extraembryonic membranes include?
- amnion, yolk sac, allantois, chorion
- form during first 2 to 3 weeks of development
48
The amnion
- develops when cells of epiblast fashion themselves into a transparent membranous sac
49
What does the amnion contain?
- amnionic fluid
50
What is the amnion's function?
- buoyant environment: protects the developing embryo against physical trauma
- helps maintain homeostatic temperature
- prevents growing embryo parts from fusing together --> freedom of movement
51
Where does amniotic fluid come from?
- initially from maternal blood
- after that, fetal urine
52
What is yolk sac formed from?
- cells of primitive gut which arrange themselves into a sac that hangs from the ventral surface of embryo
53
How is yolk sac important for humans?
- forms part of gut (digestive juice)
- source of earliest blood cells and blood vessels
54
Allantois
- small outpocketing embryonic tissue at the caudal end of yolk sac
55
Function of allantois
- structural base for umbilical cord that links embryo to placenta
- becomes a part of urinary bladder
56
What does a fully formed umbilical cord contain?
- embryonic connective tissue, umbilical arteries and veins
- covered by amniotic membrane
57
Organogenesis
- formation of organs and organ systems
58
Mean duration of pregnancy in weeks
- 38 weeks
59
Effect of pregnancy into female reproductive organs
- become increasingly vascular and engorged with blood
- increases vaginal sensitivity and sexual intensity
60
Why do breasts enlarge and engorge with blood during pregnancy?
- rising levels of estrogen and progesterone
61
What does the hormone relaxin do?
- produced by the placenta
- causes pelvic ligaments and pubic symphysis to relax, widen and become more flexible
62
How do multivitamins like folic acid help?
- reduce the risk of having a baby with neurological problems
63
Metabolic changes in the mother during pregnancy
- placenta secretes human placental lactogen (hPL) also known as human chorionic somatomammotropin (hCS)
- hPL works with estrogens and progesterones to prep breasts for lactation
- promote fetus growth and exerts glucose-sparing effect on mother
- maternal cells metabolize more fatty acids and less glucose
64
Pregnancy effect on GI system
- nausea and vomitting due to hCG, esterogen, progesterone
- heartburn due to reflux of stomach acid into esophagus
- constipation
65
Pregnancy effect on urinary system
- more urine produced
- increased metabolic rate and uterus pressing against bladder
66
Pregnancy effect on respiratory system
- nasal mucosa become edematous and congested due to estrogens
67
Pregnancy effect on cardiovascular system
- total body water rises and BV increase as much as 40% by 32 weeks
- safeguard blood loss
68
Parturition
- giving birth to the baby
69
Rise in estrogen in the last weeks of pregnancy
1. stimulate myometrial cells of uterus to form oxytocin receptors
2. promote gap junction formation between uterine smooth muscle cells
3. antagonizes progesterone;s quieting influence on uterine muscles
70
What does oxytocin do?
- causes placenta to release prostaglandins that stimulate more uterine smooth muscle gap junctions
- more contractions
71
Stages of labour
- dilation, expulsion, placental stage
72
What is the neonatal period?
- four-week period immediately after birth
73
Lactation
- production of milk by mammary glands
74
Hormonal control of lactation
- rising levels of estrogen, progesterone, hPL stimulate hypothalamus to release prolactin-releasing factors
- ant. pit. responds by secreting prolactin
75
Advantages of breast milk
- fats and ions r better absorbed and amino acids are better metabolized
- beneficial chemicals like IgA protect infant from infections
76
ulcer causing bacteria
- helicobacter pylori
