Reproduction 2 Flashcards
What are the different components of a sperm?
Head:
- Acrosome (contains enzymes for fertilization)
- Nucleus
Midpiece:
-Mitochondria
Tail (whiplike movements propel sperm)
What is spermatogenesis? Process?
Production of sperm
Process:
- Chromosomes replicate
- Meiosis I (produces spermatocytes with 2n)
- Meiosis II (Produces four spermatids with 1n)
- Differentiation (Produces spermatazoa with 1n)
How does sperm maturation occur?
Spermatazoa released into lumen of seminiferous tubules
- immotile
- 20days
Move to epididymis by peristaltic contractions and flow of lumenal fluid where they acquire motility
Move to vas deferens by peristalsis
-Remain in vas deferens until equaculation
How is the sexual response in males controlled and how does it occur?
Controlled by autonomic nervous system through spinal reflexes in phases
Phases:
- Erection - parasympathetic nervous system
- Emission - sympathetic nervous system
- Ejaculation - sympathetic nervous system
What are the receptors for sexual response in males?
Stimuli
- mechanoreceptors of penis and erogenous zones
- descending signals from higher brain centers
How does emission occur?
Response to mechanical stimulation continues from erection to emission
-Neural activity shifts from parasympathetic control to sympathetic control
- Contractions of epididymus, vas deferens and ejaculatory duct
- Secretions from seminal vesicles and prostate
- Result - movement of semen in urethra
What is the average sperm count?
Average volume of semen - 2.75ml (can be between 2-6ml)
-66million sperm/ml
therefore 180million sperm
Infertile sperm count is less than 20million
What is the function of male reproductive tracts?
- Production of sperm
- Delivery of sperm to the female
What is the function of female reproductive tracts?
- Production of ova
- Reception of sperm
- Transport of the sperm and ovum to common site for union
- Maintenance of the developing fetus until it can survive
- Giving birth (parturition)
- Nourishing the infant after birth (lactation)
What are the characteristics of the female reproductive system?
- Cyclic changes in activity (menstrual cycle)
- Restricted periods of fertility (ovulation)
- Limited gamete production (pool established at birth)
What are the female reproductive organs?
Gonads = ovaries
Reproductive tract = uterus, uterine tubes, vagina
External genetalia = vulva
Ovaries are the site of ova maturation consisting of connective tissue with follicles separate from reproductive tract
Where are the follicles and what do they contain?
Found in the ovaries and contain one ovum
What do granulosa cells do?
-Target cells of estrogen and FSH
which secrete chemical messengers in response
-Secrete inhibin which provides negative feedback to FSH secretion
-Transport nutrients to oocytes through gap junctions
-Secrete estrogens
What is the vagina?
The female organ of copulation
- Wall contains smooth muscle
- Inner surface bathed in acid fluid secretion from uterus or glands in cervix (protects against bacterial infections)
What is the uterus?
Site of fetal development
What are the uterine tubes?
Also called fallopian tubes
-Ova transported from ovaries to uterus
What is Oogenesis?
Creation of an ovum
What is the menstrual cycle?
Repeated changes in the ovary and uterus through time
Includes:
Ovarian cycle
Uterine cycle
Caused by changes in estrogen and progesterone concentrations
What are the two phases of the ovarian cycle?
- Follicular phase (mensturation approx 14 days)
- Luteal phase (Ovulation to before menstruation approx 14 days)
What occurs during the follicular phase?
A few follicles begin to develop from primordial follicles
- Oocyte grows, granulosa cells proliferate
- Dominant follicle continues development
- FSH and estrogens stimulate follicle growth and development
What occurs during the Luteal Phase?
- Ruptured follicle
- Corpus luteum secretes estrogens and progesterone
- Corpus luteum reaches max activity 10days, then degenerates
- If oocyte fertilized, degeneration does not occur
How do fraternal twins occur?
- Two or more follicles may become dominant and released at ovulation
- If both are fertilized - fraternal twins
- Also called dizygotic twin
What occurs during the menstrual phase of the uterine cycle?
- Shedding of uterine lining
- Blood flow to tissue decreases
- Tissues die and slough into vagina causing menstrual flow
- Triggered by decreased estrogens and progesterones
What occurs during the proliferative phase?
- Uterus prepares for fertilized ovum
- Endometrial lining develops, the layer grows, the glands enlarge
- Smooth muscle layer thickens
- Cervical glands secrete mucus
- Estrogens stimulate development of uterine linings
What occurs during the secretory phase?
Endometrium prepared for implantation
- Blood supply increased
- Glands enlarge and secrete glycogen-rich fluids
- Cervical secretions more sticky forming a plug
How do hormones fluctuate during the menstrual cycle?
- Estrogen is first secreted from follicle, then from the corpus luteum
- Progesterone secreted from corpus luteum
- LH and FSH secreted from anterior pituitary
- Estrogens and progesterone inhibit LH and FSH secretion
What are the actions of estrogens?
Follicular phase:
- Promote endometrial growth
- Promote oogenesis and follicle development
- Increase in LH secretion (late follicular phase)
Pregnancy and Luteal phase:
- Promote growth of duct tissue and deposition of fat in breasts
- Suppress lactation
- Increase in prolactin secretion
- Growth and contractile activity of uterine smooth muscle
- Promotion in fluid retention
What are the actions of progesterone?
During Luteal Phase and pregnancy:
- Promotes secretory-phase uterine conditions
- Suppresses uterine contractile activity
- Promotes growth of glandular tissue in breasts
- Suppresses milk production
