Special Parts: Gender. Why Have Sex?

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Stewart Hensley
5 years ago
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Why Have Sex? Lots of animals clone themselves... 100% of their genes are passed on!

1 Why Have Sex? Lots of animals clone themselves % of their genes are passed on! Sex requires sharing, it s expensive (time, mate selection, special parts, prenuptial gifts...) So why do it? Special Parts: Gender Sexual reproduction requires GENDERS What determines gender? What is the role of each gender in reproduction? These questions were debated for a LONG time...

2 Sex at the Cellular Level: Meiosis Regular (somatic) cells have 46 chromosomes (diploid); reproductive (germ) cells have 23 (haploid) Meiosis reduces the number of chromosomes by half Human gender determination Females: XX Males: XY Meiosis: Genetic variation Occurs only in diploid cells Result is 4 haploid daughter cells Involves 2 cell divisions There are 3 sources of genetic variation: 1) Independent orientation of chromosome pairs (2 23 combinations) 2) There are 2 23 X 2 23 possible combinations of gametes between 2 people. 3) Crossing over

3 Male Reproductive Anatomy Scrotum Penis Why outside? Erection reflex Why doesn t the urethra become constricted? External Genitalia Testes Exocrine function and endocrine functions Septa divide the testis into lobules; each lobule containing one to four seminiferous tubules Interstitial cells produce testosterone.

4 Duct System Duct System Duct System Epididymis Comma-shaped highly coiled tube Serves as a temporary storage site for immature sperm Epididymal walls contract to push sperm out

Duct System Duct System Vas deferens (within the spermatic cord) From epididymis to pelvic cavity, Propels sperm from storage sites to the ejaculatory duct via peristalsis Ejaculatory duct Sperm are

Secretion is full of fructose, vitamin C, prostaglandins, and other substances which nourish and activate the sperm Sperm and seminal fluid enter the urethra together during ejaculation.

5 Duct System Duct System Vas deferens (within the spermatic cord) From epididymis to pelvic cavity, Propels sperm from storage sites to the ejaculatory duct via peristalsis Ejaculatory duct Sperm are moved into the urethra via peristalsis during ejaculation Male Accessories Seminal Vesicles Located at base of bladder and produce 60% of seminal volume. Secretion is full of fructose, vitamin C, prostaglandins, and other substances which nourish and activate the sperm Sperm and seminal fluid enter the urethra together during ejaculation. Urethra Prostatic urethra Membranous urethra Penile urethra During ejaculation, the bladder sphincter constricts, keeping urine out of the urethra and sperm out of the bladder. Prostate Gland Prostate Gland Secretions help to activate sperm Bulbourethral Glands Produce a thick, clear mucus which clears the urethra of traces of acidic urine and provides lubrication for intercourse.

Semen Milky white, sticky secretion composed of sperm and accessory gland secretions Is a transport medium for sperm, provides them with nourishment and protection, and helps them swim Semen ph: 7.

6 Semen Milky white, sticky secretion composed of sperm and accessory gland secretions Is a transport medium for sperm, provides them with nourishment and protection, and helps them swim Semen ph: Acts to neutralize the female vagina (ph of 3.5-4). Antibacterial component Spermatogenesis Seminiferous tubules = sperm factories Spermatogonium = diploid stem cell. FSH stimulates the spermatogonia to produce A cells and B cells. B cells become primary spermatocytes, which will form 4 haploid spermatids.

Effects of Testosterone Determines 'maleness' Helps gonads form Brings about secondary sex characteristics Female Reproductive System Functions of the Female System: Produce one ovum each month

7 Effects of Testosterone Determines 'maleness' Helps gonads form Brings about secondary sex characteristics Female Reproductive System Functions of the Female System: Produce one ovum each month Provide a place for fertilization and implantation of a fertilized egg Support a fetus for 9 months Feed the infant after birth External Genitalia (Vulva) 1. Mons pubis Overlying the pubic symphysis for protection 2. Labia Majora and minora enclose the vaginal opening

External Genitalia Greater Vestibular Glands Secretions serve as lubricants for vaginal opening Clitoris Concentration of sensory neurons Becomes engorged with blood during sexual arousal Focus for

8 External Genitalia Greater Vestibular Glands Secretions serve as lubricants for vaginal opening Clitoris Concentration of sensory neurons Becomes engorged with blood during sexual arousal Focus for FGM procedures FGM WHO defines FGM as: Procedures involving partial or total removal of the external female genitalia or other injury to the female genital organs whether for cultural, religious or other non-therapeutic reasons. FGM is often called female circumcision implying that it is similar to male circumcision. However, the degree of cutting is far more extensive, often impairing a woman s sexual, reproductive, renal and bowel functions. FGM Resources

Ovaries Uterine (Fallopian) Tubes Typical site of

System Exocrine function Endocrine function Uterus

egg Body, fundus, cervix Layers of the uterus:

and semen during intercourse, allows for passage

9 Ovaries Uterine (Fallopian) Tubes Typical site of fertilization Fimbrae and cilia are critical Duct System Exocrine function Endocrine function Uterus Vagina Receive, retain and nourish the fertilized egg Body, fundus, cervix Layers of the uterus: Epimetrium Myometrium Endometrium Receives penis and semen during intercourse, allows for passage of baby and menstrual flow And the most important part...

15-25 lobes, which are further divided into lobules w/ areolar glands (produce milk).

10 Female Accessories Mammary Gland Function? Mammary Glands Nourish the baby with milk. Developmentally, they are modified sweat glands(!) Areola surrounds the central nipple lobes, which are further divided into lobules w/ areolar glands (produce milk). Lactiferous ducts Female Reproductive Physiology Human females are silent ovulators - which is rare! In other animals, it s an obvious event...

IF the secondary oocyte is fertilized by a sperm cell, it will undergo the second meiotic division Menstrual Cycle Days 1-5: Menses

11 Oogenesis FSH stimulates follicle development. Primary oocyte begins to go through meiosis I. Products: one polar body secondary oocyte Dominant follicle breaks free from the ovarian wall in the process of ovulation. IF the secondary oocyte is fertilized by a sperm cell, it will undergo the second meiotic division Menstrual Cycle Days 1-5: Menses Thick endometrial lining is sloughed off and it leaves the body via the vagina. Day 6-13: Proliferative Stage Repair and regrowth of the endometrium. Glands are re-formed, blood supply increases.

Menstrual Cycle Day 14: Ovulation Egg is released due to a surge of LH Day 15-28: Secretory Stage

Lack of ovarian hormones in the blood causes endometrial cells to die Preventing Pregnancy

Barriers: methods to prevent egg/sperm encounters Contraceptives: methods to prevent pregnancy by

12 Menstrual Cycle Day 14: Ovulation Egg is released due to a surge of LH Day 15-28: Secretory Stage Endometrium to increases in vascularization and gland production. Lack of ovarian hormones in the blood causes endometrial cells to die Preventing Pregnancy Contraceptive: Surgical Sterilization (vasectomy and tubal ligation) Abstinence is 100% effective Barriers: methods to prevent egg/sperm encounters Contraceptives: methods to prevent pregnancy by disrupting ovulation or fertilization (contra-conception) Contragestives: prevent implantation of an embryo in the uterus (contra-gestation)

IUD: Contragestive The Pill Contraceptive

progesterone agonists Prevent ovulation Implants

progesterone (progestin) prevents implantation

implanted and the hormone is time-released Implants

13 IUD: Contragestive The Pill Contraceptive Birth-control pills contain estrogen and progesterone agonists Prevent ovulation Implants and Injections: Contragestives Synthetic progesterone (progestin) prevents implantation Norplant (Implants) 6 rods full of progestin are implanted and the hormone is time-released Implants and Injections: Contragestives Synthetic progesterone (progestin) Depo-Provera Injections

followed by 400 ug dose of misoprostol two days later (induces uterine contractions) Clinical Conditions Prostatic

14 Emergency Contraception (EC): Contragestive Mifepristone (Mifeprex) (RU-486) Contragestive Competitive progesterone receptor antagonist FDA-approved abortifacient to terminate pregnancies of up to 49 days gestation 600 mg dose followed by 400 ug dose of misoprostol two days later (induces uterine contractions) Clinical Conditions Prostatic hypertrophy and prostate cancer Male infertility Female Infertility Cervical cancer Breast Cancer Male and female circumcision

15 1. Chocolate 2. Kava kava root 3. Yohimbe bark extracts 4. Be careful of ephedrine Check labels for: ephedra epitonin Aphrodisiacs ma huang (Chineese ephedrine) Good Reproductive Health! Aphrodite, Greek Goddess of Love

The Reproductive System

The Reproductive System The Reproductive System Gonads primary sex organs Testes in males Ovaries in females Gonads produce gametes (sex cells) and secrete hormones Sperm male gametes Ova (eggs) female