Douglas Todey

Functions The reproductive system has four functions To produce sperm and egg cells Transportation and sustenance of cells Development and nurturing of offspring Production of hormones

Reproduction Sexual Reproduction Male and female sex cells, produced by meiosis so each cell is genetically different providing for genetic variation in the offspring, combine to create an offspring Asexual Reproduction This is when one organism breaks in half and each half regrows as an exact replica of the original Examples Tapeworms Jellyfish Echinoderms

Spermatogenesis The diploid germinal cells of the seminiferous tubules produce the spermatids Multiplication Phase Germ cells increase their number by undergoing repeated mitotic divisions. As a result of this a large number of cells called sperm mother cells are formed Growth Phase The formed cells absorb nutrition from the surrounding cells of germinal epithelium and grow in size These enlarged cells are called spermatocytes

Spermatogenesis, Cont. Maturation Phase The process of reduction division or meiosis will be completed The two haploid cells that are formed after meiosis I are called secondary spermatocytes The two secondary spermatocytes undergo meiosis II to produce four cells which are called spermatids The spermatids do not undergo any further division but simply undergo metamorphosis to pro­duce the sperms At the end of maturation phase, each germinal cell would have produced four spermatids.

Spermatogenesis, Cont.

Oogenesis Multiplication Phase The primordial germ cells divide repeatedly by means of mitosis to produce a large number of daughter cells, oogonia They divide several mitotically to produce a large number of primary oocytes Growth Phase The primary oocyte increases in size considerably The cytoplasm of the oocyte is very rich in RNA, DNA, and enzymes and other cytoplasmic organelles like mitochondria, golgi complex and ribosomes are also found in large numbers

Oogenesis, Cont. Maturation Phase Oocyte undergoes meiosis to produce an egg or ovum One large haploid egg is formed along with three small polar bodies The cytoplasm divides unevenly to provide the maximum amount of nutrients for the developing embryo The polar bodies will eventually ooze out and degenerate while the egg is ready for fertilization

Oogenesis, Cont.

Menstrual and Estrous Cycles Menstrual Cycle This is a 28-day cycle in women when the egg leaves the ovary and is available to be fertilized On day 14, ovulation occurs, which is when the egg leaves the ovary Estrous Cycle The estrous cycle is the period when animals such as dogs, cattle, or horses are considered “in heat” and should be bred Females will only allow males to mate during this period to increase the chance of being bred

Menstrual Cycle The menstrual cycle is a day cycle found in both humans and primates The ovarian cycle involves the ovulation of the egg from the ovaries in which a woman then becomes fertile

Hormonal Control Women also make estrogen and progesterone hormones The synthesis and secretion of estrogens is stimulated by follicle-stimulating hormone (FSH), which is controlled by the hypothalamic gonadotropin releasing hormone(GnRH) Secretion of GnRH depends on neurons in the hypothalamus which express a gene encoding a protein of 145 amino acids. From this, several short peptides are cut collectively called kisspeptin. These are secreted and bind to G-protein-coupled receptors on the surface of the GnRH neurons stimulating them to release GnRH. However, high levels of estrogen inhibit the secretion of kisspeptin and suppress further production of those hormones

Development of the Embryo The fertilized egg starts dividing in which the cleavage of the egg determines whether it is a protostome or a deuterostome. This is called the morula Then the coelom forms in the gastrulation stage. The cells push inward and form a double layered cell wall and the hole created is called the blastopore. This group of cells is called the blastula From the blastopore Deuterostomes The mouth develops from the blastopore Protostomes The anus develops from the blastopore These blastopores are called the gastrula

Germ Layers Germ layers are the concentric layers that form various tissues and organs Ectoderm Creates the outer covering of the animal Can also make the central nervous system Endoderm Creates the digestive tract Also makes the liver and lungs Mesoderm This creates the muscles It also makes most other organs between the outer covering and the digestive tract

Infertility This means that a person cannot have a child The main symptom is the inability to become pregnant Approximately 9% of women are infertile Treatment includes education and counseling, fertility treatments, medicines to treat infections and clotting disorders, and medicines that help the woman grow and release eggs from the ovaries

Ovarian Cancer This is cancer that is found in a woman’s ovaries Symptoms include bloating or swollen belly area, difficulty eating or feeling full quickly, and pelvic or lower abdominal pain There will be approximately 22,280 new cases of ovarian cancer in 2012 and 15,500 will die of it Treatment includes surgery to remove the uterus, both ovaries, or the fallopian tubes

Sources on.html on.html of-spermatogenesis.html of-spermatogenesis.html of-oogenesis.html of-oogenesis.html sheet/menstruation.cfm sheet/menstruation.cfm AP Biology Campbell and Reece textbook