Reproductive System and Development (Male Reproductive Structures (Penile…
Reproductive System and Development
Major Events of Fetal Development
during the last trimester the fetus gains weight, that is mostly fat.
Some organs begin to function before birth and other, including the lungs, digestive system and reproductive system will function after birth.
Growth and development continues until the fetus is viable (approximately 7 months)
Skeletal muscle becomes active and the mother may feel baby movement called
(approximately 5 months)
Growth proceeds rapidly, some hair appears on head (
) and the skin becomes coated with a waxy coating called the
During fetal development, the vital organs and organ systems achieve functional capability.
Major Events of Embryonic Development
Between the 5th-8th week the head and facial fetures become more refined and reproductive organs begin to develop.
Arms and leg buds appear along the cartilaginous vertebral column during the 5th week
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
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 endoderm is the inner layer that forms the gastrointestinal tract.
The mesoderm is the middle layer will form the muscles, skeletal and reproductive system
The ectoderm is the superior germ layer which becomes the skin, sense organs, and nervous system
From the inner cell mass the embryo will develop
After implantation the trophoblasts become chorion, which will become the placenta
The outer cells of the blastula, called trophoblasts, will send finger like projections that aid in the implantation of the blastula in the uterus
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
When the 32 cell stage is reached a solid sphere of cells called a morula is formed
Shortly after fertilization, the cell begins rapid mitosis and cells begin to divide, these divisions are called cleavages and results in blastomeres
Events of the Menstrual Cycle
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
Day 14 Ovulation: the oocyte is released from the ovary into the uterine tube where it with make its way to the uterus
Day 1-13 Follicular stage: during this stage primary follicles mature into Graafian follicles
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
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 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.
Hormones of the Reproductive Systems
Progesterone- primary hormone responsible for functional layer growth after ovulation; causes increase in blood vessel distribution, uterine gland size and nutrient production
Estrogen- initiates and maintains growth of the functional layer of the endometrium
Testosterone- stimulates maturation and function of male reproductive system
Luteinizing hormone- released by the anterior pituitary, it controls ovulation of secondary oocyte from the ovarian follicle
Follicle-stimulating hormone- controls the development of both oocyte and ovarian follicles within ovaries and controls development of sperm within testes
Gonadotropin-releasing hormone is a regulatory hormone released by the hypothalamus to trigger the release of FSH and LH from the pituitary gland.
Meiosis, Spermatogenesis and Oogenesis
- the process of creating oocytes
Monthly, from puberty to menopause: if fertilized the secondary oocyte completes the second meiotic division and becomes a second polar body and ovum
Monthly, from puberty to menopause: the secondary oocyte is arrested in meiosis 2, until it is fertilized.
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.
Childhood: meiosis one is arrrested.
Before Birth: primary oocyte begin to undergo meiosis but is arrested during prophase 1.
Before Birth: the diploid oogonium undergoes mitosis to create the needed supply of parent cells
-the process of creating sperm
Spermatids develop tails and become spermatozoa
Each secondary spermatocyte undergoes meiosis 2 and 4 unique haploid spermatids
The diploid primary spermatocyte undergoes meiosis 1 and two haploid secondary spermatocytes are created.
The process starts with a diploid spermatagonium, the spermatagonium undergo continuous mitosis to create and endless supply of "parent cells"
- is sex cell division that starts with a diploid parent cell and ends with four unique haploid daughter cells.
product of meiosis 2 is 4 unique haploid gametes
Telophase 2: chromosomes become chromatin and nuclear membrane reforms.
Anaphase 2: Chromatids are separated and pulled to poles, each chromatid becomes a chromosome.
Metaphase 2: Centrioles are at opposite "poles" and spindle fibers line up chromosomes
Prophase 2: nuclear membrane breaks down, chromatin become chromosomes.
Telophase 1: Chromosomes become chromatin and nuclear membrane reforms. Product of meiosis 1 is 2 new haploid cells.
Anaphase 1: separates pairs of chromosomes by pulling them to opposite poles
Metaphase 1: Chromosome pairs line up and forms a disc in the center of cell
Prophase 1: nuclear membrane goes away, chromatin become chromosomes and chromosomes pair up into tetrads
Female Reproductive System
- the remaining part of the follicle after an egg has been secreted, produce both progesterone and estrogen.
protects and nourishes the developing baby
- carries immature oocyte, called Graafian Follicles if carrying mature oocyte
- the external genitalia of the female reproductive system
- birthing canal and receptical of penis
- the inner lining of the uterus and the site of implantation of a fertilized oocyte
- the muscular and constricted neck of the uterus
-protective in function, the minora is the inner labia and is usually hairless
- protective in function, the majora is the outer labia and is usually covered in hair
- responsible for stimulation that leads to female orgasm
- mound of hair covered skin overlying a fat pad and the pubis symphysis
- carries egg from the ovaries to the uterus. Usually the site of fertilization.
- produce oocytes that carry the maternal chromosomes.
Male Reproductive Structures
- encloses the urethra
- holds blood involved in an erection
- produces the fluid that gives semen an alkaline pH
- secrete testosterone
- produces sperm cells
- tip of penis that contains the external urethral orifice
- gives sperm a jump start into the vagina
- portion of urethra that carries both urine and semen
- transports sperm from the epididymis, up and around bladder and down into the ejaculatory duct.
- Releases fructose found in semen
- recieves sperm from the vas deferens
releases a lubricant found in semen
- stores sperm until it reaches full maturity
- responsible for spermatogenesis
- holds and regulates the temperature of the testes