meiosis and the male reproductive system
DESCRIPTION
Used to (re)ntroduce high school anatomy and physiology students to the process of meiosis / gametogenesis. More specifically, this presentation focuses on spermatogenesis and the male reproductive system anatomy.TRANSCRIPT
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Reproductive SystemOverviewMeiosis
SpermatogenesisHormone signaling in Males
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Male and female reproductive systems
Function together to produce offspring Female reproductive system nurtures developing offspring Gonads (Ovaries / Testes)
Function as endocrine glands; produce hormonesFunction as exocrine glands; produce gametes
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GametogenesisMeiotic division of cells; spermatogenesis and oogenesisOne replication of DNA, two sets of PMAT divisionsResults in Haploid cells (one of each type of chromosome)Fusion of haploid cells (fertilization) results in diploid zygote
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Possible number of chromosome combinations
= 2n
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Structures of Male Reproductive System
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Male Reproductive System
TestesPrimary organs
Develop in the abdominal pelvic cavity of fetusDescend into scrotal sac shortly before or after birth
Produce the male sex cells (sperm) Produce the male hormone testosterone
Scrotum – sac that holds the testes
Seminiferous tubulesWithin testes, site of spermatogenesis initiation
Filled with spermatogenic cells that produce sperm cells
Interstitial endocrinocyte cells produce testosterone
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Structures of Male Reproductive System
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Structures of Male Reproductive System
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Male Reproductive System: Internal Accessory Ducts
Epididymis - ductSits on top of each testisReceives spermatids from seminiferous tubulesSpermatids become sperm cells
Vas deferens - ductTube connected to epididymisCarries sperm cells to urethra
Ejaculatory ductsWithin prostate
Formed by union of seminal vesicle and vas deferens
UrethraShared terminal duct of reproductive and urinary systems
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Male Reproductive System: Internal Accessory Glands
Prostate gland Surrounds urethraProduces and secretes a milky, alkaline fluid into urethra just before ejaculationFluid protects sperm in the acidic environment of the vagina40% of semen
Seminal vesicleSecretes
Fluid rich in sugar used for energyProstaglandins – stimulate muscular contractions in female to propel sperm forward
Bulbourethral (Cowper’s) glandsProduce a alkaline mucus-like fluid
Secreted just before ejaculationNeutralizes urine acidityLubricates end of penis
SemenAlkaline mixture
NutrientsProstaglandins
1.5 to 5.0 ml per ejaculateSperm count of 40 to 250 million / ml
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Male Reproductive System:External Accessory Organs
ScrotumHolds testes away from body
3°C below body temperature
Lined with serous membrane that secrets fluid
Testes move freely
Testes separated from one another by septum
PenisShaft
Erectile tissues surround urethraGlans penis
Cone-shaped structure on end of penis
Prepuce Skin covering glans penis in uncircumcised males
FunctionsDeliver spermUrination
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SpermatogenesisSpermatogonia (46 chromosomes)
31-19
Mitosis – produces primary spermatocytes
Undergo meiosis two secondary spermatocytes
Divides – two spermatids = 4 spermatids
Develop flagella to become mature sperm cells with 23 chromosomes
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Sperm cells
HeadNucleus with 23 chromosomesAcrosome – enzyme-filled sac
Helps sperm penetrate ovum
MidpieceMitochrondria that generate cell’s energy
TailFlagellum that propels sperm forward
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Hormonal signaling in male reproduction
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