biology 30 unit 2 reproduction and development. biology 30 unit 1 introduction we will be learning...
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Unit 2Unit 2
Reproduction and Development
Biology 30
Unit 1 IntroductionUnit 1 Introduction
We will be learning about the following topics: Structure/function of male/female reproductive
systems Hormonal control of male/female reproductive cycles Birth control methods Causes of infertility/reproductive technologies Process of fertilization and development
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Reproductive SystemReproductive System
Why is reproduction so important? Ensures the survival of a species
What is reproduction? Union of a male and female sex cell to form
new genetic combinations Survival of species depends on the varied
offspring
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The Importance of ReproductionThe Importance of Reproduction
Continuation of the species
Creation of diversity within the species Adaptation Change Mutation Survival of the fittest
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Types of ReproductionTypes of Reproduction
Sexual Sex cells from a male and a female fuse to
form a new organism Involves meiosis (formation of gametes)
Asexual Organism make a copy of itself Only one “parent” involved No meiosis Occurs in prokaryotic cells and some plants
via vegetative reproduction
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The The Reproductive SystemReproductive System
Gonads: organs that produce gametes and hormones
Ducts: receive and transport gametes
Accessory glands: secrete fluids into ducts
Perineal structures: collectively known as external genitalia
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Basic Human ReproductionBasic Human Reproduction
Separate male and female systems Male gonads called testes produce sperm cells
Sperm production begins at puberty and continues into old age
Approximately 1 billion produced each day
Female gonads called ovaries produce ova (ovum, sing.)
Ova are larger than sperm Female generally releases one ovum every 28 days
following onset of menstruation and continuing to menopause
Ova are developed prior to birth, approximately (400,000)
Sperm cell fertilizes an ovum in the oviducts of the female to form a zygote which implants (attaches) to the uterine wall where it grows and develops
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Development of the Male Reproductive Development of the Male Reproductive SystemSystem
Development of male reproductive begins at 12th week of embryonic development
Prior to this male and female embryos are similar
Testes descend into the scrotum during week 30-32 of male embryonic development
Scrotum is a sac-like pouch of skin that contains the testes and is locates below the pelvic region and outside of the body.
Scrotum is 92º F (33º C) while normal body temperature is 98.6º F (37º C)
Sperm production is optimal at this lower temperature
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Problems with testis descentProblems with testis descent
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Basic Anatomy - TestesBasic Anatomy - Testes
Testes Normally two Housed in the scrotum Produce sperm cells Tube called the vas deferens carries sperm
cells to the urethra for ejaculation
Two main cell types Seminiferous cells – produce sperm (site of
meiosis) Interstitial cells – produce testosterone
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Basic Anatomy - PenisBasic Anatomy - Penis
Male sexual organ and external organ of urination
No erectile bone – erection achieved by engorgement of spongy erectile tissue chambers
Corpus cavernosa (2) Corpus spongiosum (1) forms glans penis (tip)
Stimulation of erectile tissue due to parasympathetic nervous system
Arteries leading to penis dilate Veins leaving the penis constrict due to pressure
from arteries and enlarged spongy tissue Stimulation due to sexual arousal or other
factors – full bladder, friction, dreams, etc.
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The Male Reproductive SystemThe Male Reproductive System
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Male Reproductive SystemMale Reproductive System
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Functions of structuresFunctions of structures
Scrotum – pouch of skin that stores testes located below pelvic region
Vas Deferens – carries sperm from testes to urethra
Semen – fluid that contains sperm and other chemicals
Sertoli cell – nourishes developing sperm cells
Seminiferous tubules – found in each testis where sperm cells develop
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Functions of Structures…cont’dFunctions of Structures…cont’d
Epididymus – coiled tube located on each testis where sperm cells mature
Seminal vesicles – contain substances to help sperm survive (fructose and prostaglandins)
Prostate gland – contains a substance to protect sperm cells in vagina
Cowper’s Gland – secretes mucous rich fluids prior to ejaculation
Urethra – expels both semen and urine from penis (but never at the same time)
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Sperm Cells and SpermatogenesisSperm Cells and Spermatogenesis Formed in the testicles
Nucleus contains 23 chromosomes
Half carry a Y chromosome and half carry an X chromosome
Reduced cytoplasm = reduced energy store
Mitochondria surrounds flagellum
Acrosome at tip contains enzymes to aid penetration of ovum
Sertoli cells nurture developing spermSpermatogonia
(46 chromosomes)
Spermatocytes(23 chromosomes)
Sperm cells
meiosis 9-10 days
epididymis
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SpermatogenesisSpermatogenesis
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Sperm Cells – Interesting FactsSperm Cells – Interesting Facts
Can live 1-3 hours outside the body depending on temperature, moisture, etc.
Can live 5-7 days in the cervix
Up to 500 million sperm cells per ejaculation. Below 40 M is considered infertile
Average ejaculation is 1 teaspoon (5 ml) in volume
Can be stored for many years in cryogenic storage systems
Used in artificial insemination
Tadpole like shape
Head, mid-piece, and tail
Fertility rates depend on number and motility
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Seminal FluidSeminal Fluid
Secretions from three glands make up seminal fluid
Seminal vesicle secretions (60%)
Fructose Prostagladins
Prostate secretions (30%) Alkaline buffer (basic)
Cowper’s gland (bulbourethral gland)
Pre-ejaculatory fluid
Hormonal Control Hormonal Control of the Male of the Male
Reproductive Reproductive SystemSystem
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Topics - Hormonal Control of the Topics - Hormonal Control of the Male Reproductive SystemMale Reproductive System
Where testosterone is produced
Functions of testosterone
Structures that control the production of sperm and testosterone
Hormones involved in the control of production of sperm and testosterone
Describe how production is regulated (negative feedback system) to maintain homeostasis of testosterone
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Where Testosterone is ProducedWhere Testosterone is Produced
In interstitial cells in testes
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Functions of TestosteroneFunctions of Testosterone
Stimulates spermatogenesis (production of new sperm cells)
Promotes development of secondary sex characteristics
Maturation of testes and penis Increase in sex drive Facial/body hair Growth of larnyx (deepening of voice) Secretion of body oils (acne)
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Structures that control the production of sperm and Structures that control the production of sperm and testosteronetestosterone
Hypothalamus
and Pituitary
Gland
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Hormonal Control of Male Reproductive Hormonal Control of Male Reproductive SystemSystem
GnRH (Gonadotropin-releasing hormone) produced in hypothalamus
At the pituitary, GnRH stimulates the synthesis and secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
FSH stimulates production of sperm cells in seminiferous tubules of testes
LH stimulates production of testosterone by interstitial cells (Leydig cells) of testes
Negative FB Loop: The hypothalamus detects high levels of testosterone whichlowers GnRH production in the pituitary which in turn lowers LH secretions. Thisresults in lower levels of testosterone production.
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Hormones Involved…Hormones Involved…
In the production of sperm:
Follicle Stimulating Hormone (FSH)
Acts on the Sertoli Cells in the testes (seminti to produce sperm cells
In the production of testosterone:
Luteinizing Hormone (LH)
Acts on the interstitial cells in the testes to produce testosterone
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Negative Feedback ControlNegative Feedback Control
Required to maintain constant levels of testosterone and sperm
Hypothalamus → GnRH → Pituitary → LH → Interstitial cells → testosterone produced
Hypothalamus → GnRH → Pituitary → FSH → Sertoli Cells → Sperm produced
If sperm/testosterone too high → system shuts off to decrease levels set level
If sperm/testosterone is too low → system turns on to increase levels to set level
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Hormonal Feedback/Regulation of Male Reproductive Function
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Female Female Reproductive Reproductive
SystemSystem
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Female Reproductive System DevelopmentFemale Reproductive System Development
Development of female reproductive begins at 12th week of embryonic development
Prior to this male and female embryos are similar
Paired ovaries form near the kidneys during embryonic development and remain in the abdominal region
Ovaries contain ova, or “eggs”
Ovaries also produce female sex hormones Estrogen Progesterone
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Female Reproductive System Internal (X-Female Reproductive System Internal (X-Section)Section)
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Female Reproductive System - External Female Reproductive System - External AnatomyAnatomy
Separate openings to the outside for products of the urinary and reproductive systems
Urethra Vagina
Clitoris develops from the same embryonic tissue as the penis and consists of erectile tissue
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Basic Anatomy - Female Reproductive Basic Anatomy - Female Reproductive SystemSystem
10-12 cm in length oviducts, or Fallopian tubes, connect ovaries to the uterus
Released ovum travels along oviducts via cilia
Fertilization of ovum occurs in oviduct
Oviducts join at uterus, or womb
Uterus is connected to vagina by the cervix
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The UterusThe Uterus
Composed of three main tissues:
1. Perimetrium – fibrous elastic tissue that surrounds the uterus and holds it place with ligaments
2. Myometrium – muscular lining that supports a fetus and also contracts during child birth
3. Endometrium – forms the placenta for the developing fetus. Released if no fertilization takes place – menstruation.
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Main Structures and FunctionsMain Structures and Functions
The ovaries produce the cells that become ova (eggs).
A released oocyte moves into the oviduct (or Fallopian tube) where it may be fertilized if sperm are present.
If fertilized, it completes meiosis and becomes an ovum.
If an embryo results it will attach to the lining of the uterus to complete its development.
The cervix is the opening from the uterus into the vagina. Holds fetus in place during pregnancy.
The vagina is the canal for entry of the penis and exit of menstrual flow and serves as the birth canal.
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OvariesOvaries
Each ovary contains hundreds of thousands of follicles
Follicles are the structure in the ovaries that produces the eggs and, in particular, the female sex hormones, estrogen and progesterone
Each follicle contains an oocyte An oocyte is a cell that has begun the process of
meiosis and can eventually produce an ovum (egg)
FSH and LH from the anterior pituitary create changes in the ovary during various phases of the ovarian cycle
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FolliclesFollicles
Primary follicles consist of a primary oocyte surrounded by granulosa cells
Outer layer of connective tissue surrounding the follicles is called the theca
Theca secretes androgens that are converted to estrogen in the granulosa cells
Secondary follicles secrete estrogen and nurture the secondary oocyte
Eventually forms an ovarian follicle (Graafian follicle) that ruptures and releases the ovum
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Follicle Stages in the OvaryFollicle Stages in the Ovary
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Hormones and the OvaryHormones and the Ovary
FSH causes development of the follicle during the first half of the menstrual cycle
After ovulation the follicle becomes the corpus luteum under the influence of LH
Negative feedback regulates hormone levels
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Uterine (Menstrual) CycleUterine (Menstrual) Cycle
Day 1-5: Menstruation - shedding of uterine lining - due to low hormone levels
Day 6-13: Proliferative Phase -FSH stimulates follicle which in turn secretes estrogen. Estrogen causes the endometrium to thicken.
Day 14: Ovulation
Day 15-28: Secretory Phase – LH promotes the formation of the corpus luteum within the ruptured follicle - which in turn produces progesterone, which in turn stimulates the endometrium to secrete thick nutrient-rich fluids (ready for implantation).
If no implantation then the corpus luteum degenerates as LH levels fall. Progesterone levels also fall and endometrium is no longer maintained – menses begins and cycle repeats.
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No FertilizationNo Fertilization
LH levels fall during the luteal phase
Corpus luteum degenerates
Progesterone levels fall
Uterine lining (endometrium) is no longer maintained due to low levels of progesterone
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FertilizationFertilization
Fertilization occurs in the upper portion of the oviduct and implantation occurs on the uterine wall
Embryonic cell divisions begin and the embryo produces the hormone HCG
HCG maintains the corpus luteum so that progesterone continues to be released
Uterine lining continues to thicken so the embryo can survive
HCG → human chorionic gonadotropin
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Critical Hormones in ReproductionCritical Hormones in Reproduction
FSHFSH - secreted by the anterior pituitary. Stimulates the development of an ovarian follicle in a female or the production of sperm in a male.
LHLH - produced by the anterior pituitary gland. Stmulates the development of the corpus luteum in females and the production of testosterone in males.
EstrogenEstrogen - Female sex hormone, which, along with progesterone, maintains the primary sex organs and stimulates development of the female secondary sex characteristics.
ProgesteroneProgesterone -Female sex hormone secreted by the corpus luteum of the ovary and by the placenta.
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Reproductive Reproductive Health IssuesHealth Issues
Fibroid Tumors
Ovarian and Cervical Cancer
Bartholin Cysts
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Fibroid TumorsFibroid Tumors
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Ovarian CancerOvarian Cancer
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ResourcesResources
Female Reproduction