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Reproductive System and Development (Male Reproductive Structures (Scrotum…
Reproductive System and Development
Male Reproductive Structures
Scrotum
- holds and regulates the temperature of the testes
Testes
- responsible for spermatogenesis
Epididymis
- stores sperm until it reaches full maturity
Cowper's Gland
releases a lubricant found in semen
Ejaculatory Duct
- recieves sperm from the vas deferens
Seminal Vesicle
- Releases fructose found in semen
Vas Deferens
- transports sperm from the epididymis, up and around bladder and down into the ejaculatory duct.
Penile Urethra
- portion of urethra that carries both urine and semen
Penis
- gives sperm a jump start into the vagina
Glans
- tip of penis that contains the external urethral orifice
Seminiferous Tubules
- produces sperm cells
Interstitial Cells
- secrete testosterone
Prostate Gland
- produces the fluid that gives semen an alkaline pH
Corpora Cavernosa
- holds blood involved in an erection
Corpus Spongiosum
- encloses the urethra
Female Reproductive System
Ovary
- produce oocytes that carry the maternal chromosomes.
Uterine Tube
- carries egg from the ovaries to the uterus. Usually the site of fertilization.
Mons Pubis
- mound of hair covered skin overlying a fat pad and the pubis symphysis
Clitoris
- responsible for stimulation that leads to female orgasm
Labium Majora
- protective in function, the majora is the outer labia and is usually covered in hair
Labium Minora
-protective in function, the minora is the inner labia and is usually hairless
Cervix
- the muscular and constricted neck of the uterus
Endometrium
- the inner lining of the uterus and the site of implantation of a fertilized oocyte
Vagina
- birthing canal and receptical of penis
Vulva
- the external genitalia of the female reproductive system
Follicles
- carries immature oocyte, called Graafian Follicles if carrying mature oocyte
Uterus
protects and nourishes the developing baby
Corpus Luteum
- the remaining part of the follicle after an egg has been secreted, produce both progesterone and estrogen.
Meiosis, Spermatogenesis and Oogenesis
Meiosis
- is sex cell division that starts with a diploid parent cell and ends with four unique haploid daughter cells.
Prophase 1: nuclear membrane goes away, chromatin become chromosomes and chromosomes pair up into tetrads
Metaphase 1: Chromosome pairs line up and forms a disc in the center of cell
Anaphase 1: separates pairs of chromosomes by pulling them to opposite poles
Telophase 1: Chromosomes become chromatin and nuclear membrane reforms. Product of meiosis 1 is 2 new haploid cells.
Prophase 2: nuclear membrane breaks down, chromatin become chromosomes.
Metaphase 2: Centrioles are at opposite "poles" and spindle fibers line up chromosomes
Anaphase 2: Chromatids are separated and pulled to poles, each chromatid becomes a chromosome.
Telophase 2: chromosomes become chromatin and nuclear membrane reforms.
product of meiosis 2 is 4 unique haploid gametes
Spermatogenesis
-the process of creating sperm
The process starts with a diploid spermatagonium, the spermatagonium undergo continuous mitosis to create and endless supply of "parent cells"
The diploid primary spermatocyte undergoes meiosis 1 and two haploid secondary spermatocytes are created.
Each secondary spermatocyte undergoes meiosis 2 and 4 unique haploid spermatids
Spermatids develop tails and become spermatozoa
Oogenesis
- the process of creating oocytes
Before Birth: the diploid oogonium undergoes mitosis to create the needed supply of parent cells
Before Birth: primary oocyte begin to undergo meiosis but is arrested during prophase 1.
Childhood: meiosis one is arrrested.
Monthly, from puberty to menopause: primary oocytes in mature follicle completes the first meiotic division to produce a polar body and a haploid secondary oocyte.
Monthly, from puberty to menopause: the secondary oocyte is arrested in meiosis 2, until it is fertilized.
Monthly, from puberty to menopause: if fertilized the secondary oocyte completes the second meiotic division and becomes a second polar body and ovum
Hormones of the Reproductive Systems
Gonadotropin-releasing hormone is a regulatory hormone released by the hypothalamus to trigger the release of FSH and LH from the pituitary gland.
Follicle-stimulating hormone- controls the development of both oocyte and ovarian follicles within ovaries and controls development of sperm within testes
Luteinizing hormone- released by the anterior pituitary, it controls ovulation of secondary oocyte from the ovarian follicle
Testosterone- stimulates maturation and function of male reproductive system
Estrogen- initiates and maintains growth of the functional layer of the endometrium
Progesterone- primary hormone responsible for functional layer growth after ovulation; causes increase in blood vessel distribution, uterine gland size and nutrient production
Events of the Menstrual Cycle
(Uterine Cycle)
Day 1-5 is the menstual phase: this phase s marked by the shedding of the functional layer of the endometrium and last through the period of menstrual bleeding.
Day 6-14 is the proliferating phase: during this phase the development of a new functional layer of the endometrium overlaps the time of follicle growth and estrogen secretion of the ovaries.
Day 15-28 is the secretory phase: during this phase increased vascularization and development of uterine glands occur primarily in response to progesterone secretion from the corpus luteum
Ovarian Cycle
Day 1-13 Follicular stage: during this stage primary follicles mature into Graafian follicles
Day 14 Ovulation: the oocyte is released from the ovary into the uterine tube where it with make its way to the uterus
Day 15-28 Luteal phase: Corpus luteum forms from ruptured follicle and begins to secrete progesterone and estrogen, if egg is not fertilized the luteum regresses and becomes a corpus albicans
Hormone Levels
Major Events of Embryonic Development
Shortly after fertilization, the cell begins rapid mitosis and cells begin to divide, these divisions are called cleavages and results in blastomeres
When the 32 cell stage is reached a solid sphere of cells called a morula is formed
When the morula reaches the uterus some cells cluster near one side leaving a hallow area in the center, and it is now called a blastula
The outer cells of the blastula, called trophoblasts, will send finger like projections that aid in the implantation of the blastula in the uterus
After implantation the trophoblasts become chorion, which will become the placenta
From the inner cell mass the embryo will develop
At about 10-14 days the blastula becomes a gastrula and the inner cell mass is transformed into the embryonic disc, which becomes the embryo
The ectoderm is the superior germ layer which becomes the skin, sense organs, and nervous system
The mesoderm is the middle layer will form the muscles, skeletal and reproductive system
The endoderm is the inner layer that forms the gastrointestinal tract.
The brain and spinal cord are the first to form, then the heart (late 3rd week) and many of the other organs form by the 4th week. along with a cartilage skeleton and muscles
Arms and leg buds appear along the cartilaginous vertebral column during the 5th week
Between the 5th-8th week the head and facial fetures become more refined and reproductive organs begin to develop.
Major Events of Fetal Development
During fetal development, the vital organs and organ systems achieve functional capability.
Growth proceeds rapidly, some hair appears on head (
Lanugo
) and the skin becomes coated with a waxy coating called the
vernix caseosa
Skeletal muscle becomes active and the mother may feel baby movement called
quickening
(approximately 5 months)
Growth and development continues until the fetus is viable (approximately 7 months)
Some organs begin to function before birth and other, including the lungs, digestive system and reproductive system will function after birth.
during the last trimester the fetus gains weight, that is mostly fat.
