Human Reproductive Biology Flashcards
(48 cards)
Male
Gonads
Testes
Male
Sex glands
Seminal vesicles
Prostate gland
Bulbo-urethral gland
Male
Ducts
Epipydidymis
Vas Deferens
Ejaculatory duct
Urethra
Female
Gonads
Ovaries Fallopian tubes / oviducts Uterus Vagina Uvula / Pudendum
Reproductive Cells
Testes
Produce germ cells
Spermatozoa
Reproductive Cells
Ovaries
Produce germ cells
Oocytes
- Known as gametes.
- Produced via meiosis
What is Spermatogenesis
Production of Sperm:
- initiated at start of puberty
- ~300 million produced per day
Occurs in seminiferous tubules.
Seminiferous Epithelium
Formed by two cell populations
- spermatogenic germ line cells
- sertoli supporting cells
What are Interstitial Cells?
- Adjacent to seminiferous tubules
- Stimulated by LH to produce testosterone
- Concentrate testosterone 20-200 times the level found in blood via ABP (Androgen Binding Protein).
Hormones and Spermatogenesis
Process
Hypothalamus releases GnRH (gonadotropin releasing hormone)
Anterior pituitary releases FSH & LH
LH = Interstitial cells + Testosterone FSH = Sertoli cells + Spermatogonia - Inhibin
LH + FSH = Spermatogenesis
Spermatogenesis Process
Germinal Epithelium (lining of seminiferous tubule)
Primordial sperm (2n) (Mitosis) Spermatogonium (2n) (Mitosis / Differentiation) Primary Spermatocyte (2n) (Meiosis) Secondary Spermatocyte (n) (Meiosis II) Spermatid (n) + Spermatazoon (n) (Spermiogenesis)
Germ Line Stem Cells
- Spermatagonial stem cells can be isolated from testis tissue
- They can be transplanted into a recipients testis
- The transplanted cells to develop into competent sperm
Deposition of Semen in Humans
- Semen is deposited in the vagina, at the cervical Os.
- Semen coagulates due to sex gland enzymes
- Coagulant retains spermatozoa at the cervical os
- Coagulant acts as alkaline buffer in acidic vagina (pH 5.7)
- Within one minute sperm are detected in the cervix.
- 99% of sperm are lost from vagina
What is puberty?
Immature individuals acquires the physical and behavioural attributes which will allow them to reproduce.
What are Twin Studies?
Genetic influences are the single largest factor accounting for variation in pubertal development.
What are external factors effecting?
Stressful events
Endocrine disrupting chemicals
Adiposity
Rule of Nutrition in Pubertal Initiation
Puberty is later in countries which have “sub-optimal” socioeconomic status.
Causes of delayed puberty:
- Malnutrition e.g. Anorexia Nervosa
- Elite athletes e.g. gymnasts & ballerinas
Advanced puberty associated with moderate obesity.
What is the menstrual cycle?
- Transport gametes to site of fertilisation
- Provide suitable site for embryo implantation
- Ends in endometrial shedding. (Releases period)
Menstrual Cycle Steps
1) Menstruation begins
2) FSH is released
3) Eggs begin to mature in ovary
4) Endometrium builds up
5) LH is released
6) Oestrogen released
7) One egg is more mature than others. Maturation of others slows.
8) Egg is mature
9) Ovulation occurs
10) Ovum travels down oviduct
11) Progesterone released
12) Fertilisation may now occur
13) Corpus luteum breaks down
14) Progesterone drops
15) Oestrogen drops
16) Endometrium breaks down
Menstruation summarised
Decreased oestrogen and progesterone
Leads to endometrial shredding
What is the proliferative / follicular stage?
Increase in FSH
Ovum matures
Increase in oestrogen
Endometrium thickening
As oestrogen peaks, pituitary gland shows FSH production and releases LH instead.
What is ovulation?
Ovum bursts from follicle - travels down Fallopian tube
What is the secretory / luteal phase?
Corpus luteum
Increase in progesterone
Increased oestrogen
Increased endometrium