Human Reproduction

Objectives: 1. To identify the anatomy of the Male Reproductive System 2. To understand the hormonal controls in sperm production 3. To identify the anatomy of the Female Reproductive System 4. To understand the hormonal controls involved in the 4 stages of the Menstrual Cycle

Let’s Compare Male System – simple! Male System – simple! Female System – complicated !! Female System – complicated !! Let’s look at the Male System first. Let’s look at the Male System first. All it does is produce 2-4 million sperm cells per day starting at puberty and continuing until the day you die! All it does is produce 2-4 million sperm cells per day starting at puberty and continuing until the day you die!

Male Anatomy

Cross-section of the Seminiferous Tubule

Anatomy of the Seminiferous Tubule Spermatagonia – 2n reproductive cells that undergo meiosis to produce haploid sperm cells Spermatagonia – 2n reproductive cells that undergo meiosis to produce haploid sperm cells Interstitial Cells – Produce testosterone Interstitial Cells – Produce testosterone Sertoli Cells – provide nourishment for the developing sperm cells Sertoli Cells – provide nourishment for the developing sperm cells

Endocrine System

Hormonal Control of Sperm Production It all starts in your…..BRAIN!! It all starts in your…..BRAIN!! The Hypothalamus secretes many hormones into your blood including GnRH which stimulates the Pituitary to secrete 2 hormones called: FSH – Follicle Stimulating Hormone LH – Lutenizing Hormone The Hypothalamus secretes many hormones into your blood including GnRH which stimulates the Pituitary to secrete 2 hormones called: FSH – Follicle Stimulating Hormone LH – Lutenizing Hormone FSH – stimulates sperm production FSH – stimulates sperm production LH – stimulates testosterone production LH – stimulates testosterone production

Testosterone Promotes more sperm production AND the development of secondary sex characteristics Promotes more sperm production AND the development of secondary sex characteristics Negative Feedback Negative Feedback As levels of testosterone rise the hypothalamus detects the levels and…… As levels of testosterone rise the hypothalamus detects the levels and…… …stops the production of GnRH from the Hypothalamus which…… …stops the production of GnRH from the Hypothalamus which…… …stops the production of LH from the Pituitary which…….. …stops the production of LH from the Pituitary which…….. …reduces the production of testosterone from the Interstitial Cells …reduces the production of testosterone from the Interstitial Cells This is called Negative Feedback This is called Negative Feedback

Hormonal Feedback Hypothalamus Negative feedback Testosterone production Releasing hormone Anterior pituitary FSH LH Sperm production

Positive feedback As dropping testosterone levels are detected, the _____________ starts to release ___________, which causes the __________gland to release ____________, which increases the production of ______________. As dropping testosterone levels are detected, the _____________ starts to release ___________, which causes the __________gland to release ____________, which increases the production of ______________. This is called Positive Feedback This is called Positive Feedback

Sperm Cells

Semen Semen, not to be confused with “seaman”, is the fluid that sperm cells swim in. Semen, not to be confused with “seaman”, is the fluid that sperm cells swim in. There are three glands that secrete the fluids: There are three glands that secrete the fluids: Prostate gland – secretes an alkaline buffer that neutralizes the acidic environment of the vagina. Prostate gland – secretes an alkaline buffer that neutralizes the acidic environment of the vagina. Seminal vesicles – secrete a fructose solution that provides energy for the sperm cells Seminal vesicles – secrete a fructose solution that provides energy for the sperm cells Cowper’s gland – secretes a mucous that lines the urethra to prevent the sperm from contacting any urine residue Cowper’s gland – secretes a mucous that lines the urethra to prevent the sperm from contacting any urine residue

Female Anatomy

It all starts in the Brain (again)!

Menstrual Cycle 28 day cycle that begins at puberty and continues until menopause 28 day cycle that begins at puberty and continues until menopause Consists of 4 stages: Consists of 4 stages: Menstruation (your period) Menstruation (your period) Follicle Stage Follicle Stage Ovulation Ovulation Corpus Luteum Stage Corpus Luteum Stage

#1 Menstruation 4-6 days 4-6 days Endometrium and unfertilized egg are removed from the uterus. Endometrium and unfertilized egg are removed from the uterus. Pituitary gland releases FSH which stimulates the follicles in the ovaries. Pituitary gland releases FSH which stimulates the follicles in the ovaries.

Ovary and Follicles

#2 Follicle Stage One follicle usually “becomes the chosen one” and continues to enlarge. One follicle usually “becomes the chosen one” and continues to enlarge. The ovaries release Estrogen which thickens the endometrium. The ovaries release Estrogen which thickens the endometrium. Rising levels of Estrogen send negative feedback to the Hypothalamus (GnRH) and Pituitary which stops the production of FSH. Rising levels of Estrogen send negative feedback to the Hypothalamus (GnRH) and Pituitary which stops the production of FSH. Positive feedback initiates the release of LH from the Pituitary. Positive feedback initiates the release of LH from the Pituitary.

#3 Ovulation Around day 14, LH levels are at their highest and cause the stimulated follicle to rupture and release it’s egg. Around day 14, LH levels are at their highest and cause the stimulated follicle to rupture and release it’s egg. The egg is swept by the fimbria into the oviduct The egg is swept by the fimbria into the oviduct You are most fertile at this point. (Vulnerable to becoming pregnant!) You are most fertile at this point. (Vulnerable to becoming pregnant!)

#4 Corpus Luteum Stage The ruptured follicle changes into a yellowish structure called the Corpus Luteum. The ruptured follicle changes into a yellowish structure called the Corpus Luteum. It releases estrogen and progesterone (pregnancy hormone) It releases estrogen and progesterone (pregnancy hormone) If pregnancy results: If pregnancy results: The zygote releases hCG (Human Chorionic Gonadotropin Hormone) sending PF to the CL to continue to release Estrogen and Progesterone The zygote releases hCG (Human Chorionic Gonadotropin Hormone) sending PF to the CL to continue to release Estrogen and Progesterone Estrogen and progesterone levels stay high, preventing the release of FSH by the pituitary (NF) Estrogen and progesterone levels stay high, preventing the release of FSH by the pituitary (NF)

Corpus Luteum Stage

#4 Corpus Luteum Stage If pregnancy does not occur: If pregnancy does not occur: No hCG results in NF, causing; No hCG results in NF, causing; Estrogen and progesterone levels drop, causing the endometrium to deteriorate and menstruation begins again. Estrogen and progesterone levels drop, causing the endometrium to deteriorate and menstruation begins again. Dropping levels of estrogen and progesterone cause the pituitary to begin releasing FSH (PF) Dropping levels of estrogen and progesterone cause the pituitary to begin releasing FSH (PF)

Birth Control Pills Trick your body into thinking it is pregnant. Trick your body into thinking it is pregnant. If your body thinks it is pregnant, you won’t ovulate. If your body thinks it is pregnant, you won’t ovulate. Without an egg being released, you cannot become pregnant. Without an egg being released, you cannot become pregnant. Each pill has different amounts of progesterone. Each pill has different amounts of progesterone. The “pill” can be prescribed to regulate your period because of the specific levels of hormones found in each pill The “pill” can be prescribed to regulate your period because of the specific levels of hormones found in each pill

Pregnancy Tests Check for the presence of hCG (Human Chorionic Gonadotropin) in the mother’s urine Check for the presence of hCG (Human Chorionic Gonadotropin) in the mother’s urine The fertilized egg releases hCG The fertilized egg releases hCG

Feedback If you are Pregnant: hCG continues to be produced causing positive feedback to the ovaries to continue to produce estrogen and progesterone for the next 40 weeks. If you are Pregnant: hCG continues to be produced causing positive feedback to the ovaries to continue to produce estrogen and progesterone for the next 40 weeks. If you are not Pregnant: no hCG causes negative feedback to the ovaries stopping the production of estrogen and progesterone, and you start your period. If you are not Pregnant: no hCG causes negative feedback to the ovaries stopping the production of estrogen and progesterone, and you start your period.

Terms to remember: Fertilization – union of egg and sperm inside the oviduct. Fertilization and Implantation Fertilization – union of egg and sperm inside the oviduct. Fertilization and ImplantationFertilization and ImplantationFertilization and Implantation Implantation – attachment of fertilized egg into the endometrium 6 to 8 days after fertilization. Implantation – attachment of fertilized egg into the endometrium 6 to 8 days after fertilization. Gastrulation – 16 to 18 days after fertilization Gastrulation – 16 to 18 days after fertilization Embryo – term used to refer to the developing ball of cells after gastrulation up to 8 weeks. Embryo – term used to refer to the developing ball of cells after gastrulation up to 8 weeks. Fetus – after 8-10 weeks Fetus – after 8-10 weeks Make Room For the Baby Make Room For the Baby Make Room For the Baby Make Room For the Baby

4 weeks 5 months 8 months

Embryological Development