Mammalian Reproduction

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Mammalian Reproduction

• Group 2
• III-Cesium

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Male reproductive anatomy (overview)

• Internal reproductive organs
• Gonads produce gametes and hormones
• Accessory glands secrete products essential for
  sperm movement
• Ducts carry the sperm and glandular secretions
• External reproductive organs
• scrotum
• penis

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Testes the male gonads

• Consist of seminiferous tubules interspersed with
  Leydig cells
• Seminiferous tubules sperm production ( approx.
  200 mil/day)
• Leydig cells production of androgens
  (testosterone)
• Following production, sperm pass into the
  epididymis

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• Epididymis
• Composed of 6 metre-long coiled tubules
• Stores sperm for about 20 days
• sperm mature and gain
• Ability to fertilize
• Motility
• Vas deferens
• Two ducts, each running from the epididymis to
  the back of the urinary bladder
• Ends in an ejaculatory duct
• Opens into the urethra
• During ejaculation, sperm are propelled from the
  epididymis through the vas deferens

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• Urethra
• Tube that runs from the bladder through the
  prostate gland to the end of the penis
• Functions in both the reproductive and the
  excretory systems
• Exit point for semen and urine
• Closing of muscular sphincters

1. Urinary Bladder2. Pelvic Urethra3. Penile
Urethra
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Accessory glands

• Add secretions to semen
• Semen fluid ejaculated
• Seminal vesicles
• a pair of glands opening into the urethra
• contributes 60 of the semen (3-5mL)
• Supplies a thick, yellowish, alkaline fluid
• Mucus
• Fructose sugar (energy)
• Coagulating enzyme
• Ascorbic acid
• prostaglandins

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• 2) Prostate gland
• largest of the glands
• Secretes a thin, milky-white fluid directly into
  the urethra
• Anti-coagulant enzymes
• Citrate (a sperm nutrient)
• Slightly acidic
• 3) Bulbourethral glands
• Pair of glands along the urethra
• Produce a clear, alkaline mucus
• Secreted into the urethra before ejaculation
• Neutralize acidic urine
• Also carries some sperm

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External organs

• Scrotum
• Fold of the body wall
• Holds the testes outside the abdominal cavity
• Sperm production cannot occur at normal body
  temperature (98.6F)
• Temperature in scrotum 95-97F
• Not present in all mammals (e.g. whales,
  elephants)
• Penis
• Serves to deposit the sperm in the female genital
  tract
• 3 cylinders of spongy erectile tissue
• Engorges with blood during arousal
• Forms an erection necessary for insertion
• Baculum rodents, raccoons, walruses
• Bone that helps stiffen the penis
• Glans penis head of the penis
• Covered by a prepuce (foreskin)
• Also functions in the excretory system

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Female Reproductive anatomy (an overview)

• Internal reproductive organs
• Gonads produce the eggs
• Ducts and chambers
• channel the gametes
• Accommodate the embryo and fetus
• External Reproductive organs
• Clitoris
• Labia minora
• Labia majora

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Ovaries the female gonads

• Lie in the abdominal cavity
• Enclosed in a tough, protective capsule
• Contain the follicles (approx 400 000)
• Follicles one egg cell and its emveloping layers
  of follicle cells
• Formed before birth
• Follicle cells nourish and protect the cells
• Produce estrogens
• Release the egg during ovulation
• Ovulation release of an egg from the ovaries
  during the menstrual cycle
• Corpus lutaeum composed of remaining follicular
  tissue
• Grows within the ovary
• Secretes estrogens and progesterone
• Disintegrates if egg is not fertilized

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• Oviduct (fallopian tube)
• Duct that opens with a funnel-like entrance
• Lined with cilia
• Collects the egg upon release
• Conveys the egg cell from the ovaries to the
  uterus
• Uterus (womb)
• Thick, muscular organ
• Expands during pregnancy
• Endometrium
• Inner lining of the uterus
• Highly vascularized

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• Cervix neck of the uterus
• opens into the vagina
• Vagina
• Thin-walled chamber
• Functions
• Birth canal
• Repository of sperm during intercourse
• Hymen partial covering of the vagina
• Ruptured during copulation/intense physical
  activity

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• Vestibule
• Contains the vaginal and urethral openings
• Bordered by the labia minora
• Slender skin folds
• Enclosed by the labia majora
• Thick, fatty ridges
• Clitoris
• Located at the front edge of the vestibule
• Engorges with blood during arousal
• Consists of
• Rounded glans (covered by a prepuce)
• Supporting shaft
• Erectile tissue

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• Bartholins glands
• Secrete mucus into the vestibule
• Lubrication
• Facilitates intercourse
• Mammary glands
• Consist of
• Small sacs of epithelial tissue
• Secrete milk
• Adipose tissue
• Function only in women

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Human sexual response

• Terms
• Coitus sexual intercourse
• Vasocongestion swelling of body tissues due to
  increased arterial blood flow
• Myotonia increased muscle tension

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The sexual cycle is divided into 4 phases

• 1) excitement
• Readies the vagina and penis for coitus
• Involves
• Enlargement of testes, labia, breasts
• Vaginal lubrication
• Vasocongestion of vagina and penis
• Myotonia in arms and legs
• 2) plateau phase
• Continues responses begun in excitement phase
• Involves
• Increase in breathing and heart rates
• Formation of a depression at the back of the
  vagina
• For the reception of sperm

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• 3) Orgasm rhythmic, involuntary contractions of
  reproductive structures
• 2 phases
• Emission contraction of glands and ducts
• Forces sperm into the urethra
• Ejaculation expulsion of semen (2-5 mL 100-650
  mil sperm)
• Prostaglandins thin mucus at the opening of the
  female uterus
• Stimulates contraction of uterine muscles, moving
  up the coagulated semen
• Anticoagulants liquify the semen
• Sperm swim through the female tract

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• 4) Resolution final phase
• Reverses the effects of the previous stages
• Vasocongested organs relax

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Structure of the sperm cell

• Produced via spermatogenesis
• Occurs in the seminiferous tubules
• Consists of
• Head
• Haploid nucleus
• Acrosome anterior-most organelle
• Contains enzymes sperm penetration
• Varied shapes (oval, spherical, comma)
• Neck
• Middle piece
• Mitochondrion ATP for tail movement
• Tail (flagellum)

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Structure of the egg cell

• Oogenesis production of ova
• Ova mature, unfertilized egg cells
• Consists of
• Yolk cell substance
• Germinal vesicle nucleus
• Germinal spot nucleolus
• Zona pellucida thick, transparent envelope
  surrounding the egg cell
• Corona radiata surrounds the zona pellucida
• Layers of cells derived from the follicle

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FIN