reproductive systems Flashcards
1
Q
what is reproduction
A
- biological process by which new individual organisms (offspring) are produced from their parents, two types (asexual and sexual)
2
Q
what are the types of asexual reproduction and the advantages / disadvantages
A
- asexual: offspring originates from a single organism and inherits the parents’ genes
- gemmation: formation of small buds on the surface of progenitor which develops into a new individual
- fragmentation: new organism growing from fragments of progenitor
- parthenogenesis: offspring develops from unfertilised eggs (arthropods, amphibians)
- advantages: very quick, no gamete formation necessary, advantage for small populations, not very complex, less energy, survival in a stable environment
- disadvantages: offspring is clone of parent (little genetic diversity), environment usually not stable long term (adaptation / evolution), often struggle for existence as well as overcrowding
3
Q
what is sexual reproduction and the advantages / disadvantages
A
- gametes: haploid chromosome set
- gonads: primary sex organs, male testes (spermatozoa), female ovaries (ova)
- sex hormones: males (androgens) and females (oestrogen and progesterone)
- fertilisation: leads to a diploid zygote (humans 2n)
- advantages: introduces genetic diversity, survival in a changing environment
- disadvantages: cost intensive (energy), only 50% of genome contribute to offspring, few offspring
4
Q
describe the male reproductive tract
A
- penis: copulatory organ, root, shaft, glans penis (tip), foreskin (prepuce), corpus spongiosum (surrounds urethra) and corpus cavernosa (paired dorsal erectile bodies)
- erection: vascular event, sexual arousal, nerves release nitric oxide, vasodilation, BF to corpora cavernosa
- semen: milky white mixture of sperm / accessory gland secretions, 2-5 mL ejaculation
- scrotum: sac of skin and superficial fascia, hangs outside abdominopelvic cavity, contains testes, midline septum divides scrotum in two
5
Q
what are the testes
A
- testes: within the scrotum, surrounded by two tunics
- tunica vaginalis (outer layer derived from peritoneum)
- tunica albuginea (inner layer forms fibrous capsule)
- septa: divides the testis into ~250 lobules
- seminiferous tubules: each lobule contains 1-4 tubules, these produce sperm (gametes)
- spermatogonium: sperm ripens from this into mature sperm
- interstitial tissue: produce hormones (androgens)
- cryptorchidism: undescended testes, treated at 6 months with special operation, if not treated risk of infertility, testicular torsion, cancers
6
Q
describe temperature control of the testes
A
- kept constantly 3ºC lower than core body temperature
- necessary for sperm production, two sets of muscles contract scrotum towards abdominal cavity when cold
- dartos muscle: smooth, wrinkles scrotal skin, pulls close to body
- cremaster muscles: bands of skeletal that elevate testes
- pampiniform plexus: testicular artery from abdomen and testicular vein entering abdomen from scrotum lie in torturous plexus
- countercurrent heat exchange: heat exchange in the plexus decreases temp of blood entering testes, blood leaving testes is warmed by contraction
- spermatogenesis: greatly affected by temperature of testicle
7
Q
describe the male duct system
A
- seminiferous tubules: produce, maintain and store sperm
- straight tubules: form due to converging of seminiferous tubules, convey sperm into rete testis
- rete testis: tubular network on inner seminiferous tubules
- efferent ductules: sperm leave the testis to enter the head of epididymis
- epididymis: single highly coiled tube, about 6m long, maturation of sperm, passage of sperm 2-6 days, microvilli absorb testicular fluid and pass nutrients to stored sperm (head, body, tail)
- vas / ductus deferens: sperm transport, smooth muscle in walls propels sperm from epididymis to urethra, sperm storage, palpable, about 45cm long
- ejaculatory duct: enters prostate, and there it empties into the urethra
- urethra: terminal portion of the male duct system, conveys both urine and semen
8
Q
what are the accessory glands of male reproductive system
A
prostate gland:
- encircles urethra inferior to bladder, size of peach pit
- single gland, contributes ~30% of seminal fluid
- contains enzymes, secretes milky, slightly acid fluid
seminal vesicles:
- paired glands, on posterior bladder surface, contribute ~65% of seminal fluid, alkaline, prostaglandins, clotting proteins and fructose
- smooth muscle that contracts during ejaculation, duct of seminal gland joins ductus deferens to form ejaculatory duct
bulbourethral gland:
- cowper’s gland, pea-sized glands inferior to prostate, paired glands, contribute <5% of seminal fluid, lubricate glans penis (tip)
- alkalinity neutralises acidic urine in urethra, pre-ejaculatory fluid, produce thick, clear mucus during sexual arousal
9
Q
describe female internal genitalia
A
- located in pelvic cavity; include ovaries and duct system (uterine tubes, uterus, cervix and vagina)
10
Q
describe female external genitalia
A
- mons pubis: fatty area overlying pubic symphysis
- labia majora: sebaceous glands, protection
- labia minora: erectile connective tissue
- clitoris: highly sensitive to touch / temp, nerves, BV, erectile tissue
- perineum: muscle between vaginal opening and anal canal, abundance of nerve endings, sensitive to touch
- vaginal opening: vestibule, inferior to urethral opening, may be covered by hymen
- urethral opening: vestibule, urination
- bartholin’s glands: major vestibular / paravaginal glands, alkalinity promotes sperm survival, lubrication during coitus
- skene’s glands: minor vestibular / paraurethral glands, lubrication during coitus
11
Q
describe the female duct system
A
- uterine tube system does not have direct contact with ovaries
- includes two uterine tubes (fallopian tubes), one uterus and one vagina
12
Q
what are the uterine tubes
A
- F: receive ovulated oocyte, site of fertilisation, early nourishment of embryo, transports oocyte to the uterus (smooth muscle peristalsis and ciliary action)
- peg cells: non-ciliated cells, nourish oocyte and sperm
- S: isthmus, ampulla and infundibulum with fimbriae, ~10cm long and extends from area of ovary to superolateral region of uterus
- externally: covered by peritoneum and supported by a short mesentery
13
Q
what is the uterus / uterine blood supply
A
- structure: body, fundus, isthmus, uterine wall ~1.5cm thick (endometrium, myometrium, perimetrium), cervix (inferior), cervical canal
blood supply: - abdominal aorta
- uterine arteries: ascend sides of uterus and send branches in the myometrium
- radial branches: descend into the endometrium and give rise to straight arteries (to stratum basalis) and spiral arteries (to stratum functionalis)
14
Q
what is the vagina
A
- S: elastic muscular tube, extends from cervix to exterior of the body, vaginal discharge (mucous secretions from the cervix and vagina)
- F: receives the penis during coitus, acidic environment (protection)
15
Q
what are the ovaries
A
- F: produce gametes (ova), secrete female steroids, estradiol / oestrogen and progesterone
- S: no connection between fimbriae and ovaries
- ovary held in place by ovarian, suspensory and mesovarium ligaments
- flattened oval surrounded by fibrous tunica albuginea, covered by germinal cuboidal epithelial outer layer
- blood supply: ovarian arteries and ovarian branch of the uterine arteries
- inner medulla: large BV and nerves
- outer cortex: ovarian follicle (oocyte surrounded by follicle and granulosa cells)
