Animal Reproductive Structures and Functions - MALES Flashcards
Human Male Reproductive Anatomy
has both external (testes, penis) and internal (vas deferens, seminal vesicles, prostate gland, bulbourethral gland) structures
- scrotum: carries and supports testes
- penis: copulating organ
- testes: produces sperm + male hormones
- seminal vesicles: contribute to semen production
- prostate gland: contribute to semen production
- bulbourethral glands: clean urethra at ejaculation
Male Sexual Maturity + Puberty
human males become capable of reproduction at sexual maturity, which follows puberty. during puberty, the hypothalamus signals the pituitary gland to produce 2 hormones: FSH + LH
- FSH + LH stimulate the testes to produce sperm + testosterone, which initiate development of secondary sex characteristics + testes to begin producing mature sperm
Testes
sites of sperm development + maturation; located in the scrotum
- develop from the same tissue that produces ovaries. In terrestrial mammals, the cells that produce the testes migrate from within the body cavity to become external to the body during development
- scrotum + penis are external to land mammals + kept at 2C lower than body temperature to maintain sperm motility
- sperm are warmed to body temperatures when deposited in the female reproductive tract. This causes them to swim before losing motility after several hours at body temperature
Seminiferous Tubules
Sperm is produced here, and sperm mature as they proceed from the periphery to the lumen of these tubules; regulated by:
1. Sertoli Cells
2. Cells of Leydig
Sertoli Cells
protect sperm stem cells and promote their development
Cells of Leydig
produce testosterone + regulate sperm development
Structures + Sperm Travel
- When the sperm develop flagella + are nearly mature, they leave the testes and enter the EPIDIYMAS, a structure that wraps around the testes + location where sperm mature
- During ejaculation, the sperm leave the epididymis + enter the VAS DEFERENS, which carries the sperm + forms the ejaculatory duct with the seminal vesicles duct
Semen
mixture of sperm, spermatic duct secretion, and fluids from accessory glands that contribute to most of the semen’s volume.
GLANDS:
1. Seminal Vesicles
2. Prostate Gland
3. Bulbourethral Gland
Seminal Vesicles
pair of glands that make a thick, yellowish, and alkaline solution
- since sperm is only motile in an alkaline environment, a basic pH is important to reverse vaginal environment acidity
- to solution contains mucus, fructose (an energy source for sperm cells), a coagulating hormone prostaglandins (help stimulate uterus smooth muscle contractions)
- %60 of semen
Prostate Gland
muscle + gland
- the muscle provides the force for ejaculation to occur
- the glandular tissue makes a thin, milky fluid that contains citrate (stimulates sperm motility), enzymes, and prostate-specific antigen (PSA)
- PSA is a proteolytic enzyme that helps liquify the ejaculate minutes after release
- %30 of semen
Bulbourethral Gland
releases its secretion just before the release of the bulk of the semen
- the mucous secretions help lubricate + neutralize any acid residue in the urethra left over from urine
- secretions can contain few sperm; since these are BEFORE, withdrawal of the penis from the vagina to prevent pregnancy may not work if sperm is present in these secretions
Spermatogenesis
occurs in the seminiferous tubules in the testes
- sperm stem cells (SPERMATOGONIA) are present at birth but are inactive until puberty when hormones cause the activation of the spermatogonia and the continuous production of sperm
Spermatogenesis: Process
- A spermatocyte (sperm precursor) undergoes meiosis to produce four haploid spermatids (immature sperm)
- Once a spermatid develops a flagellum, it is a SPERM CELL
- 4 sperm cells result from one spermatocyte that goes through meiosis
Hormonal Control of Spermatogenesis: FSH
stimulates the activity of the Sertoli cells to nourish the developing sperm + promote development
- Sertoli cells are within the seminiferous tubules, and play an analogous role to follicle cells in the ovaries
Hormonal Control of Spermatogenesis: LH
stimulates Leydig cells to produce testosterone, which promotes spermatogenesis
- Leydig cells are located in the testes, outside the seminiferous tubules
Hormonal Control of Spermatogenesis: Testosterone
Stimulates spermatogenesis by promoting maturation of the sperm after completing meiosis
Hormonal Control of Spermatogenesis
the hormones interact in a NEGATIVE FEEDBACK LOOP
- when sperm number gets too high, high testosterone levels cause Sertoli cells to release the hormone INHIBIN, which acts on the hypothalamus + pituitary gland to inhibit the release of FSH + LH
- Sertoli cells stop releasing inhibin eventually, causing sperm numbers to increase again
Oogenesis VS Spermatogenesis: Initiation
- Egg production begins during embryonic development (before birth), then is arrested during Meiosis until puberty
- Sperm production does not begin until after puberty
Oogenesis VS Spermatogenesis: Completion
- egg production is not usually complete until after fertilization
- sperm production is complete prior to ejaculation
Oogenesis VS Spermatogenesis: Number
- Egg production results in only 1 egg from each egg stem cell
- 4 sperm result from each sperm stem cell
Oogenesis VS Spermatogenesis: Timing
- Once puberty occurs, egg production occurs one at a time at each menstrual cycle
- Sperm production is continuous in a “conveyor belt” process
Contraception
categorized by whether they block gamete production or gamete union (fertilization)
Contraception: Blocking Gamete Production
hormone-based birth control methods block gamete production but are only available for female gamete production
- Hormone-Based Birth Control
- Intrauterine Devices (IUDs)
- Emergency Contraception
Hormone-Based Birth Control
uses SYNTHETIC PROGESTERONE, which inhibits the production of FSH + LH, thus preventing an egg from maturing/being released
- when paired with estrogen, its FHS + LH inhibition is enhanced
- EX: the pill, skin implants
