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gonads
aka testes: produce sperm & secrete hormones
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Ducts in the male reproductive system & role
- Epididymis: site of sperm maturation
- ductus deferens
- ejaculatory ducts
- urethra
- AID in transport and storing sperm, assisting their maturation and conveying them to exterior
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Accessory glands in male reproductive system & role
- Seminal vesicles
- prostate
- bulbourethral glands
- AID in adding secretions to semen
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Supporting stuctures in male reproductive system
Scrotum supports testes & penis delivers sperm to female reproductive tract
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Scrotal Septum
- Internally divides scrotum into 2 sacs, each w/single testis
- Made of subcutaneous layer & dartos muscle
- Cremaster muscle is associated w/each testis
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Sperm production conditions
- Require 2-3celcius below core body temp to grow
- Cremaster & dartos muscle contract or relax to help achieve this
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Testicles
- Sperm produced here thru SPERMATOGENESIS
- Each of 200-300 lobules contain 1-3 seminiferous tubules
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Sperm forming cells (in order from beginning to maturation)
primary spermatocytes -> secondary spermatocytes -> spermatids -> sperm cells -> lumen
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Sertoli cells or sustenacular cells
- Support cells through:
- nourishing spermatocytes, spermatids & sperm
- Phagocytizing excess spermatid cytoplasm
- Controlling movements of spermatogenic cells
- Releasing sperm into lumen
- Produce fluid for sperm transport
- Secrete Inhibin
- Regulate effects of Testosterone & FSH
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Leydig cells location & role
- found between seminiferous tubules
- Help secrete Testosterone
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Spermatogenesis cycle
- Takes 65-75 days
- 1. spermatogonia (2n): Sperm undergo mitosis & some development
- 2. primary spermatocytes (2n): each duplicates its DNA
- 3. Meiosis 1 (n): homologous pairs line up, crossing over occurs. 2 haploid cells at end of Meiosis 1..each chromosome has 2 chromatids
- 4. Meisosis 2 (n): the 2 chromatids seperate into spermatids form (4 haploid cells)
- cells remain attached by CYTOPLASMIC Bridges
- 5. Spermiogenesis: spherical spermatids into elongated SPERM. Acrosome and flagella form, mitochondria multiply.
- Sertoli cells dispose of excess cytoplasm
- Spermiation: releasing from connections to Sertoli cells
- sperm not yet able to swim
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How many sperm go through spermatogenesis per day
300mil sperm
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How long can sperm survive in female reproductive tract
48hrs
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Sperm Anatomy
- Head:
- contains nucleus & 23 chromosomes (haploid - n). Acrosome also here - a vesicle with oocyte penetrating enzymes.
- Tail:
- neck contains centrioles forming microtubules comprising remainder of tail
- Middle piece has mitochondria
- Principle piece is longest portion
- End piece is the terminal portion
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Hormone Levels and roles to spermatogenesis at puberty
- secretion of GnRH INCREASES
- stimulates anterior pituitary to INCREASE secretion of LH and FSH
- LH stimulates Leydig cells to secrete testosterone...which suppresses further LH & GnRH (via neg feedback)
- Testosterone is then converted to DHT via Enzyme 5 alpha-reductase
- FSH and testosterone act on SERTOLI cells to stimulate secretion of androgen-binding protein (ABP)
- Sertoli cells release INHIBIT, inhibiting FSH
- Testosterone stimulates spermatogenesis
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Androgens (testosterone & DHT) role
- DHT: stimulates Devel. of EXTERNAL genitalia
- stimulate devel. of male sex characteristics (organs & 2ndary sex char @ puberty)
- contribute to male sex BEHAVIOR
- contribute to Spermatogenesis
- Contribute to Sex DRIVE (libido)
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Epididymis
- Site of sperm maturation: where it acquires motility & ability to fertilize
- Sperm storage (for several months)
- Continues on as ductus (vas) deferens
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Ductus (Vas) Deferens
- Conveys sperm during arousal thru peristaltic contractions
- Sperm storage (for several months)
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Ejaculatory Ducts
- Union of ducts from seminal vesicle & ampulla of ductus (vas) deferens
- ends in Prostatic urethra
- Ejects sperm & seminal vesicle secretions just before release of semen into urethra
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Urethra
- shared terminal duct of reproductive & urinary systems
- Ends @ urethral orifice
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Seminal Vesicles
- contain 60% of semen volume
- Secrete alkaline fluid (contains fructose, clotting proteins from blood)
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Prostate
- contains 25% of semen volume
- Secretes milky, acidic fluid (citric acid, proteolytic enzymes, acid phosphatase & seminalplasmin (antibiotic)
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Bulbourethral glands
- Secretes alklaine fluid that PROTECTS passing sperm by NEUTRALIZING acids from urine (in urethra)
- Mucus lubricates end of penis & lining of urethra
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Erection physiology
- Parasympathetic fibers release & cause local production of Nitric oxide (NO)
- NO causes smooth muscle in arterioles to RELAX & dilate, allowing large amounts of BLOOD to enter penis.
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