Unit 12: Reproduction Flashcards
Testes and scrotum
Male gonad
- Produce sperm
- Found in a sac called scrotum, which suspends the testes outside of the body. The scrotum can bring the testes closer or farther away from the body to regulate the temperature.
Seminiferous tubules
Testes are composed of compartments, in which contains sets of 3 tightly coiled seminiferous tubules. These are sites of spermatogenesis, the production of sperm.
Interstitial cells
Cells found between the seminiferous tubules. Secretes testosterone.
Epididymis
Tightly coiled duct lying just outside each testis.
-Stores sperm as they mature
Ductus vas deferens
Long tube that starts from the epididymis, pass through the abdominal cavity, curves around the bladder and leads into an ejaculatory duct.
- Stores sperm
- Conducts sperm from the testes to the uterus
Urethra
Tube that the ejaculatory duct leads into
-Conducts sperm out of the body
Prostate gland
A single doughnut shaped gland that surround the upper portion of the urethra just below the bladder
-Contributes basic fluid to seminal fluid
Bulbourethral gland
Pair of pea-sized organs that lie below the prostate gland
-Contributes mucoid fluid to seminal fluid
Seminal vesicles
Lies at the base of the bladder, each has a duct that joins with a vas deferens
-Contributes nutrients and fluid to seminal fluid
Sperm structure
- Head: contains the nucleus, with 23 chromosomes.
- Acrosome: a cap covering the head; contains hydrolytic enzymes so that sperm may penetrate the egg
- Midpiece: contains mitochondria to produce energy for the movement of the tail
- Tail: structure of a flagella, provides mobility
Seminal fluid function
- Slightly basic pH to counteract the acid environment in the vagina. Sperm are more viable in a basic environment
- Contains fructose to provide energy for the sperm to swim
- Contains prostaglandins to cause the uterus to contract; this helps propel the sperm towards the egg
- Contains mucous which provides a protective medium for the sperm and lubrication during sexual intercourse
Testosterone function
- Essential for development of primary sex organs
- Essential for development of sperm
- During puberty, brings about and maintains male sex characteristics (deeper voice, prominent Adam’s apple, broader shoulders, maturation of penis/testes, aggression, muscular strength)
- Cause development of noticeable facial, armpit, chest, and pubic hair
Gonadotropin releasing hormone (GnRH)
Hormone released by the hypothalamus
Causes the anterior pituitary to release FSH and LH
Follicle-stimulating hormone (FSH)
Promotes spermatogenesis in the seminiferous tubules
Promotes the development of a follicle in the ovary
Luteinizing hormone (LH)
Promotes production of testosterone in the interstitial cells.
Promotes the development of the corpus luteum
Hormonal regulation of testosterone
- Testosterone levels are regulated by negative feedback mechanism:
i) Increased testosterone levels in blood -> less LH -> less testosterone
ii) Decreased testosterone levels -> more LH -> more testosterone
Ovaries
Female gonad
- Pair of grape-like organs, with each ovary lying on either side of the upper pelvic cavity
- Each alternate to produce one egg per month
- Produce reproductive hormones
Follicles
Small sacs of fluid found on the outside layer of the ovaries
-Each contains an immature egg, called an oocyte
Corpus luteum
Glandlike structure developed from a follicle that has lost its oocyte through ovulation
-Produces sex hormones
Oviduct
Two-arm like organ that extends from the uterus to the ovaries
- Site of fertilization (sperm fusing with egg)
- Conducts the fertilized egg towards the uterus
Uterus
Thick-walled, muscular organ lying and tipping over the urinary bladder
- Site of implantation (embryo embeds itself in the uterus wall)
- Site of the development of the embryo
Cervix
Narrow end of uterus leading to the vagina
-Dilates at birth to allow the passage of the baby from the uterus into the vagina
Vagina
Tube that lies at a 45-degree angle from the cervix
- Female organ of sexual intercourse; receives the penis
- Serves as a birth canal, as well as an exit for menstrual flow
Vulva
- Vulva: The external female genital organ
Consists of:
i) Labia majora: Two large, hair-covered protective folds of skin
ii) Labia minora: Two small, protective folds of skin lying just inside the labia majora
iii) Clitoris: Female organ of sexual arousal; comparable to the male penis, contains a shaft of erectile tissue that swells with blood during sexual stimulation
Ovarian cycle: Follicular phase
Days 1-13
- Hypothalamus releases GnRH
- GnRH stimulates the secretion of FSH by the anterior pituitary
- FSH promotes the development of a follicle in the ovary
- Developing follicle starts to secrete estrogen
- Oogenesis (meiosis) occurs, resulting in the oocyte dividing into a secondary oocyte and a polar body
- The chromosome count goes from 46 -> 23 – this is the egg
- The follicle matures – known as the vesicular follicle
Ovarian cycle: Ovulation
Day 14
- Surge in estrogen levels triggers an LH spike
- LH spike causes the vesicular follicle to burst and the egg to be released -> ovulation
- Increasing estrogen levels exert negative feedback to the hypothalamus/anterior gland so that FSH levels decrease and the follicular phase ends
Ovarian cycle: Luteal phase
- LH is secreted by the anterior pituitary, in the same way as the FSH
- LH promotes the development of the corpus luteum
- Corpus luteum secretes progesterone and some estrogen
- Increasing progesterone levels exert negative feedback so that LH levels decrease and the luteal phase ends.
- i) No fertilization: Corpus luteum will degenerate
ii) If fertilization/implantation occur: Corpus luteum continue to secrete hormones for 3-4 months, until the placenta can take over
Ovarian cycle vs the Uterine cycle
Ovarian: The development of follicle, ovulation, and corpus luteum
Uterine: Changes in the endometrium – the lining of the uterus, due to the hormones secreted by the ovary during the ovarian cycle.
Uterine cycle: Menstruation
Days 1-5
- Low levels of all female sex hormones, the corpus luteum has just been degenerated
- Causes the endometrium to disintegrate and its blood vessels to rupture
- Blood and disintegrated tissue, known as the menses, passes out of the vagina
Uterine cycle: Proliferative phase
Days 6-13
- A new developing follicle secretes estrogen
- Increasing levels of estrogen cause the endometrium to thicken, and become more vascular/glandular
Uterine cycle: Secretory phase
Days 14-28
- Corpus luteum secretes progesterone and some estrogen
- Increasing levels of progesterone cause the endometrium to double/triple in thickness
- The endometrium becomes highly vascularized, and the uterine glands mature
- The uterus is now ready for implantation of the embryo
Human chorionic gonadotropic hormone (HCG)
Produced by the placenta, after implantation
Prevents the breakdown of the corpus luteum, which maintains the production of progesterone that keeps the endometrium from breaking down.
Estrogen/Progesterone function
Main female sex hormones
Estrogen: Development of the sex organs, responsible for body hair development, fat distribution beneath the skin, etc during puberty.
Both are responsible for breast development
