a&p ii unit 5: reproductive system

Name the primary reproductive organs, the gametes produced, and the sex hormones secreted by males and females.

General processes that produce the gametes, production of hormones, and maturation of reproductive capability:

Gonads – paired primary reproductive organs that produce gametes

•Ovaries in females produce oocytes

•Testes in males produce sperm

Sex Hormones – produced by gonads

Define puberty, and explain how it is hormonally triggered.

Puberty – the time during adolescence when reproductive organs in both sexes mature, gametes mature, and gonads begin secreting sex hormones.

Gonadotropin‐Releasing Hormone (GnRH) secretion from the hypothalamus initiates puberty.

•Triggers the anterior pituitary to secrete Follicle‐Stimulating Hormone (FSH) and Luteinizing Hormone (LH).

•FSH and LH trigger the gonads to produce sex hormones → start the processes of sexual maturation and gamete production.

Gamete release differs in females and males: females typically release one oocyte monthly — males typically produce approximately 100 million sperm cells daily

Define gametogenesis.

Gametogenesis – process of forming sex cells (gametes)

•Female gametes = secondary oocytes, which become ova briefly after fertilization

•Male gametes = sperm

Describe the chromosomal makeup of somatic cells and gametes; explain why gametes must contain a haploid number of chromosomes.

Chromosomes – Large DNA molecules that contain genes as parts of their DNA sequences

Genes – provide the genetic blueprints/instructions responsible for traits (Chromosomes are the molecules of heredity and must be passed on to subsequent generations)

Human Somatic (Body) Cells – contain 23 pairs of chromosomes (total of 46)

•Diploid cells (2n), since contain two copies of the chromosomes

•Chromosomes 1 to 22 = autosomes, two of each

•Somatic cells also contain two sex chromosomes, designated X and Y. (XX = female sex / XY = male sex)

The somatic cells inherited one set of 23 chromosomes from the individual’s mother, and the other set of 23 from the father.

Gametes are haploid cells (n) – one set of 23 chromosomes

•Sperm (n) + Ovum (n) combine their 23 chromosomes to form the first 2n cell of a new individual at fertilization (called a zygote) (One set of 23 chromosomes from the sperm and one set from the ovum)

Describe the basic differences between mitosis and meiosis.

Mitosis – process used in somatic cell division.

•All 46 chromosomes are replicated (2n cell has 46 duplicated chromosomes).

•During cell division, each daughter cell receives a full set of 46 chromosomes.

•2n Cell → two 2n daughter cells (each with one set of 46 chromosomes)

Meiosis – process used to create haploid gametes from a diploid cell.

•All 46 chromosomes are replicated at the beginning.

•Two cell divisions take place (Meiosis I and II) to create four haploid gametes.

•First cell division: 2n Cell → two n Cells with 23 duplicated chromosomes apiece.

•Second cell division Two n Cells with duplicated chromosomes → two gametes with 23 single chromosomes apiece

Describe the purposes and outcomes of Meiosis I and Meiosis II during gamete formation.

meiosis I: starts with a 2n diploid cell, the 46 chromosomes are duplicated to form sister chromatids, the 23 pairs of duplicated chromosomes line up in the center of the cell, one set of 23 duplicated chromosomes gets pulled into one daughter cell, and the other set gets pulled into the other daughter cell. RESULT = TWO daughter cells, each with 23 pair of DUPLICATED CHROMOSOMES (sister chromatids still attached to each other).

meiosis II: starts with the two cells from Meiosis I, each with 23 duplicated chromosomes (sister chromatids) still attached to each other, The 23 duplicated chromosomes line up in the centers of the two cells, The two cells each divide into two new cells with a single copy of 23 chromosomes, At the end of Meiosis II, there are FOUR daughter cells with 23 single chromosomes (one copy of the 22 autosomes, one sex chromosome, either X or Y).

Define chromosomal nondisjunction, and explain possible consequences.

Nondisjunction – either homologous chromosome pairs or sister chromatids fail to separate properly during a phase of meiosis.

•Both components move into one cell → one gamete has an extra chromosome, and the other lacks one.

•After fertilization, the zygote can have 47 chromosomes (trisomy) or 45 chromosomes (monosomy).

•Most of these errors are lethal, but some allow survival.

•Trisomy 21 = Downs Syndrome.

Name the female reproductive system organs, and describe their basic functions.

Ovaries – primary female reproductive organs

Accessory Female Reproductive Organs:

•Uterine (Fallopian) Tubes – transport secondary oocytes toward the uterus; normal sites of fertilization

•Uterus – site of implantation of the developing embryo; sustains embryo/fetus during pregnancy

•Vagina – receives semen during sexual intercourse

•External Genitalia

•Mammary Glands

Describe the structure of the ovaries.

•Paired, oval organs in the pelvic cavity

•Anchored in the pelvic cavity by connect tissue sheets and cords

•Each is supplied by an ovarian artery and vein (gonadal artery and vein).

•Uterine tubes connect the ovaries to the uterus.

Internal Features: Thin epithelial covering (germinal epithelium)

•Tunica albuginea – dense connective tissue capsule

•Cortex – contains ovarian follicles and connective tissue

•Medulla – blood vessels, nerves, areolar loose connective tissue

Describe the structure and development of the different stages of ovarian follicles.

ovarian follicles: cortex contains thousands of ovarian follicles

•consist of a large oocyte surrounded by much smaller follicle cells (later called granulosa cells)

Follicle stages: Primordial Follicles, Primary Follicles, Secondary Follicles, Antral Follicles (Vesicular Follicles), Mature Follicles (Graafian Follicles)

•Post‐ovulation follicles: corpus luteum and corpus albicans

Primordial Follicles: Earliest form

•Primary Oocyte (2n, diploid cell) surrounded by flattened follicle cells (Primary Oocyte – cell that has started Meiosis I but has paused)(About 1.5 million of these are present from birth.

Primary Follicles: primary oocyte plus a single layer of cuboidal follicle cells (now called granulosa cells)

•First appear during puberty, Secrete estrogen as they mature, which stimulates changes in the uterine lining

•Zona pellucida – ring of glycoprotein surrounding the primary oocyte

Describe the structure and development of the different stages of ovarian follicles.

Secondary Follicles: form from primary follicles

•Primary Oocyte in the center plus several layers of granulosa cells

•Thecal cells (connective tissue cells) surround the outside (Granulosa and thecal cells influence hormone production and control follicle development)

Antral (Vesicular or Tertiary) Follicles: develop from secondary follicles

•Contain an antrum = fluid‐filled space

•Note more layers of granulosa cells and a layer of them surrounding the zona pellucida called the corona radiata.

Mature (Graafian) Follicles: develop from antral/vesicular follicles

•Contains a secondary oocyte, more layers of granulosa cells, larger antrum

•Typically only one develops each month

•So large that may be visible as a bump protruding through the wall of the ovary

•Ruptures and releases the secondary oocyte into the uterine tube = ovulation

Describe the structure and functions of the corpus luteum and corpus albicans.

Corpus Luteum

•Yellowish in color

•Develops from the leftover remnants of a mature follicle after it ruptures and releases the secondary oocyte

•Secretes progesterone and estrogen

•Stimulates uterine lining development to prepare for implantation of a fertilized oocyte

Corpus Albicans

•Whitish in color

•Connective tissue scar that develops after a corpus luteum degrades at the end of a monthly cycle; most are completely resorbed

Describe the steps of oogenesis and where they occur.

oogenesis: maturation of a primary oocyte to a secondary oocyte in an ovary

•Be careful with follicle names and oocyte names – they don’t always match!

•Begins in a female fetus before birth: Oogonia inside primordial follicles (diploid) divide by mitosis and become primary oocytes (these begin Meiosis I but pause).

•Many primordial follicles regress during childhood when the ovaries are inactive. At puberty, about 200,000 to 400,000 remain.

Describe the phases of the ovarian cycle, including changes to the oocytes, changes to the follicles, and the steps of meiosis.

Follicular Phase – days 1 to 13

•About 20 primordial follicles have developed into primary follicles up to one year in advance.

•Follicles secrete inhibin, which inhibits FSH secretion (negative feedback) and prevents too many ovarian follicles from developing.

•A few primary follicles mature into secondary follicles.

•Typically only one secondary follicle per cycle develops into an antral (vesicular follicle), which develops into a mature follicle that ovulates.

•The primary oocyte inside an antral follicle finishes Meiosis I and becomes a secondary oocyte as the antral follicle becomes a mature follicle (just before ovulation).

•Primary Oocyte – diploid cell with 46 duplicated chromosomes

•Meiosis I occurs, producing two daughter cells with 23 duplicated chromosomes, One cell is the secondary oocyte that ovulates, The other is a polar body that degenerates, along with its 23 duplicated chromosomes. The secondary oocyte starts Meiosis II, but pauses

Describe the phases of the ovarian cycle, including changes to the oocytes, changes to the follicles, and the steps of meiosis. Describe the function of the corpus luteum and what happens when it degrades at the end of the ovarian cycle if a pregnancy does not occur.

Ovulation – day 14 of a 28‐day ovarian cycle

•secondary oocyte released from an ovary into the associated uterine tube as the mature follicle swells and ruptures

•typically only one per cycle

•occurs when there is a surge/peak in LH from the anterior pituitary

Luteal Phase – days 15‐28, after ovulation

Remaining follicle cells transform into the corpus luteum.

The corpus luteum secretes estrogen and progesterone:

•build and stabilize the uterine lining, necessary for implantation of a fertilized egg, secretes inhibin, which reduces secretion of FSH and LH to prevent a new cycle from beginning, without fertilization of the secondary oocyte, degrades and becomes a corpus albicans.

As corpus luteum degrades → estrogen and progesterone levels drop.

•Triggers menstruation (shedding of the uterine lining).

Describe the hormonal regulation of the ovarian cycle.

1. Hypothalamus secretes GnRH.

2. GnRH stimulates secretion of FSH and LH from the anterior pituitary (levels are high at the beginning of a monthly cycle).

•FSH and LH stimulate development of the ovarian follicles, along with chemical signals from the oocyte and follicle cells.

3. Negative Feedback: maturing ovarian follicles secrete inhibin (lowers FSH secretion) and estrogen (inhibits both the hypothalamus and anterior pituitary).

4. Estrogen secreted by maturing follicles triggers an antral follicle to become a mature follicle (usually just one per month).

5. The mature follicle produces a higher amount of estrogen, which actually stimulates the hypothalamus and anterior pituitary.

6. The anterior pituitary releases a surge of LH, which triggers ovulation.

Describe the hormonal regulation of the ovarian cycle.

7. After ovulation, the leftover granulosa cells of the mature follicle become the corpus luteum.

8. The corpus luteum secretes large amounts of progesterone, estrogen, and inhibin.

•Progesterone and estrogen stimulate development of the uterine lining.

•All three inhibit the hypothalamus and anterior pituitary so that a new round of follicle development and ovulation doesn’t occur (in case pregnancy happens).

9. If pregnancy occurs: the corpus luteum remains alive and secretes hormones that maintain the uterine lining.

•Human Chorionic Gonadotropin (hCG) from the developing embryo stimulates the corpus luteum to stay alive.

If no pregnancy occurs, everything starts over:

•The corpus luteum degrades.

•Estrogen and progesterone levels drop.

•FSH and LH levels rise.

•A new cycle can begin, and the uterine lining from this cycle is shed (menstruation).

Describe the basic structure and function of the uterine tubes.

uterine tubes - also called oviducts

•Extend from the uterus to the ovaries

Infundibulum – funnel‐shaped wider part near the ovary

•Fimbriae are finger‐like projections extending toward the ovary

•Receives the secondary oocyte when it ovulates.

•Muscular tube allowing passage of the secondary oocyte or fertilized oocyte to the uterus

•Normal location of fertilization

Describe the basic structure and function of the uterus, including its layers.

•After fertilization, the pre‐embryo implants into the uterus.

•Supports, protects, and nourishes the developing embryo/fetus

•Placenta – vascular organ that develops in a pregnant uterus to allow gas, nutrient, and waste exchanges between the mother’s blood and embryo/fetus’ blood.

•The uterus contracts and sheds its inner lining each cycle if pregnancy does not occur (menstruation).

Perimetrium – serous membrane covering on the outside

Myometrium – smooth muscle and thickest layer

Endometrium – inner lining that undergoes changes during the monthly cycle; composed of two layers itself:

•Basal Layer – permanent layer closest to the myometrium; few monthly changes

•Functional Layer – closest to the lumen of the uterus; thickens with each cycle and is shed during menstruation if pregnancy does not occur.

Describe the basic structure and function of the vagina.

vagina: muscular organ connecting the uterus to the outside of the body, about four inches long on average

•Receives the penis during sexual intercourse

•Passageway for menstruation

Three layers:

•Mucosa – inner mucosal lining; acidic pH

•Muscularis – middle smooth muscle layer

•Adventitia (fibrous layer) – connective tissue covering

Vaginal Orifice – opening to the outside of the body

Describe the problems associated with an ectopic pregnancy.

Pregnancy with a fertilized oocyte/developing embryo implanted somewhere other than the inner lining of the uterus.

•Tubal Pregnancy – implantation along the inner lining of a uterine tube

•The uterine tube will likely rupture after about 8 weeks → massive bleeding into the abdominopelvic cavity.

Describe the three phases of uterine/menstrual cycle.

Cyclical changes of the uterine lining, influenced by estrogen and progesterone.

•Secreted by the follicles and corpus luteum

Three Phases:

•Menstrual Phase – at the beginning of each cycle; shedding the previous endometrial lining

•Proliferative Phase

•Secretory Phase

Relate the phases of the ovarian cycle to the phases of the uterine/menstrual cycle.

Menstrual Phase – typically days 1 to 5 of the cycle (follicular phase)

•functional layer of the endometrium is shed.

•evident by menstrual flow/bleeding.

Proliferative Phase – approximately days 6 to 14; ends when ovulation occurs (follicular phase, ovulation)

•thickening/development of the new functional layer for this cycle.

•coincides with follicle maturation and estrogen secretion by them.

Secretory Phase – approximately days 15 to 28 (almost always 14 days in length) (luteal phase)

•vascularization and development of uterine glands in the functional layer, primarily in response to progesterone from the corpus luteum.

If pregnancy does not occur, the corpus luteum dies → estrogen/progesterone levels drop → functional layer of the endometrium sheds (beginning a new cycle).

Describe the problems associated with endometriosis.

endometriosis: Occurs when the endometrial lining of the uterus grows outward into the abdominopelvic cavity, likely through the uterine tubes.

•Attaches to surfaces of organs and the inner lining of the uterine tubes.

•Growth cycling and breakdown occur with hormonal changes, but contents cannot be released through the vagina → very painful.

•Scar tissue can form in the uterine tubes and cause fertility problems.

State the primary cause of cervical cancer and how it can be prevented.

cervical cancer: cancer that develops in the mucosal lining of the cervix.

•Most commonly associated with past infection with Human Papillomaviruses.

•Gardasil and Cervarix vaccines can prevent HPV infection and reduce risk of cervical cancer.

•Papanicolaou (Pap) Smear – epithelial cells are scraped from the cervical mucosa → examined for abnormal characteristics.

Describe the structures and functions of the external female genitalia.

Vulva – collective terms for the external female genitalia

Mons Pubis – skin and adipose tissue covered with pubic hair

Labia majora – paired, thickened folds of skin and connective tissue

Labia minora – paired folds immediately internal to the labia majora

Vestibule – space between the labia minora

Urethral Opening – located on the vestibule

Vaginal Orifice – also located on the vestibule

Bulb of the Vestibule – erectile tissues on either side of the vaginal orifice

Greater Vestibular Glands – secrete mucous that lubricates the vagina during sexual intercourse

Clitoris – erectile structure that fills with blood during sexual arousal

Describe the structure and function of the mammary glands.

mammary glands: produce breast milk

•Divided into lobes, which are divided into smaller sections called lobules.

•Alveoli – units inside the lobules that produce milk and secrete it into small ducts

•Lactiferous Ducts – collect milk from smaller ducts (one per lobe)  enlarge near the nipple into lactiferous sinuses

•Nipple – location where milk is released

•Lactation – milk production; covered in Chapter 29

Describe breast cancer development and its risk factors.

•Affects 1 in 8 American women and some men.

•Risk factors – genetic predisposition, specific genetic mutations, obesity, longer span between menarche and menopause, never having been pregnant, late age at first pregnancy

•Most associated with increased estrogen exposure over time.

•Develop from the epithelial linings of the ducts and lobules of the mammary glands.

•Mammogram – X‐ray of the breast that can detect breast cancers early.

Describe the female sexual response.

Excitement Phase – parasympathetic nerves stimulate mammary glands, clitoris, vaginal wall, bulbs of the vestibule, and labia  become engorged with blood

•clitoris swells and becomes sensitive to touch.

•heart rate, blood pressure, respiratory rate increase

Orgasm – vagina and uterus contract rhythmically; helps propel sperm cells forward from the vagina into the uterus

Resolution Phase – follows orgasm, reproductive organs return to normal state, but a new excitement phase can begin quickly

Name the male reproductive organs, and describe their basic functions.

Testes – primary reproductive organs in males.

Accessory reproductive organs: Ducts and tubules leading from the testes to the penis:

•R&L Epididymis

•R&L Ductus (Vas) deferens

•R&L Ejaculatory Duct

•Urethra

Male accessory glands:

•Prostate gland

•R&L Seminal vesicle

•R&L Bulbourethral gland

•Penis

Describe the structure and functions of the scrotum, including responses based on temperature changes.

Skin covered sac between the thighs, houses the two testes; keeps the testes cooler (better for sperm production)

•Scrotum wall – composed of a layer of skin, a layer of fascia deep to the skin, and a layer of smooth muscle (dartos muscle) deep to the fascia.

•Spermatic cord – bundle of structures extending from the inguinal canal in the inferior abdominal wall to the testes. Includes: fascia and a muscular layer (cremaster muscle), the ductus deferens, nerves, the testicular artery (gonadal artery) and a vein plexus.

•When temperatures are high → dartos and cremaster muscles relax, testes move inferiorly to stay cooler.

•When temperatures are cold → muscles contract, testes move closer to the pelvis to stay warmer

Describe the structure of the testes.

testes: primary male reproductive organs, housed inside the scrotum

•Produce sperm and androgens (male sex hormones, mainly testosterone)

•Covered with serous membrane (tunica vaginalis) derived from the peritoneal membrane

•Tunica albuginea – tough, fibrous capsule deep to the tunica vaginalis (projects inward to form septa that divide the testis into lobules)

•Seminiferous tubules – highly convoluted tubules inside the lobules; sites of spermatogenesis

•Spaces between the tubules contain interstitial cells (produce testosterone)

Describe the structure of the seminiferous tubules and the cell types present.

Seminiferous tubules fill up much of the space inside the testes. Thick‐walled structures containing:

Sustenacular Cells (Sertoli Cells, Nurse Cells): Provide protective environment for developing sperm cells, Secrete inhibin

Dividing cells that develop into sperm cells through spermatogenesis and spermiogenesis:

•Spermatogonia

•Primary and Secondary Spermatocytes

•Spermatids

•Sperm in the lumen of the tubule

Interstitial Cells – between tubules, secrete testosterone

Explain the steps of spermatogenesis, including the phases of Meiosis.

•Spermatogonia (diploid) are located near the edges of the seminiferous tubules. Divide by mitosis to produce a new spermatogonium and a primary spermatocyte.

•Primary Spermatocytes (diploid) undergo Meiosis I to produce two secondary spermatocytes.

•Secondary Spermatocytes (haploid with 23 duplicated chromosomes) undergo Meiosis II to produce four spermatids (haploid with 23 single chromosomes)

•Spermatids – undergo changes to become sperm cells

Define spermiogenesis, and distinguish between this phase and spermatogenesis.

Spermiogenesis – spermatids undergo changes to become spermatozoa or sperm

Spermatogenesis is the continuous, hormone-driven process in the male testes that transforms diploid germ cells into haploid spermatozoa

Spermiogenesis is the final, non-dividing maturation phase of spermatogenesis where round, haploid spermatids differentiate into specialized, motile spermatozoa (sperm)

Describe the structure of a sperm cell and the functions of its main parts.

Spermiogenesis – spermatids undergo changes to become spermatozoa or sperm.

•acrosome cap develops – contains digestive enzymes used when the sperm cell penetrates a secondary oocyte during fertilization

•midpiece develops – contains mitochondria for ATP production

•flagellum develops – tail used for motility

Sperm at this stage look mature, but not fully functional until later in pathway through male duct system.

Explain the hormonal regulation of testosterone production and sperm development.

•GnRH is secreted by the hypothalamus.

•GnRH stimulates secretion of FSH and LH from the anterior pituitary.

•LH stimulates interstitial cells (in between the walls of the seminiferous tubules in the testes) to secrete testosterone.

•FSH stimulates the Sustentacular Cells to secrete Androgen Binding Protein (ABP).

•ABP binds testosterone and maintains high concentration of it around the seminiferous tubules → stimulates spermatogenesis.

•testosterone inhibits GnRH secretion and anterior pituitary sensitivity to it.

•Sustentacular Cells secrete inhibin as sperm levels rise → inhibits FS secretion

List the functions of testosterone.

1. Stimulates spermatogenesis

2. Increases sexual desire and sensitivity

3. Stimulates secondary sex characteristics: Growth and development of pubic hair, Axillary hair growth, Growth of the larynx → deeper voice, Facial hair development

Describe the structure and function of the left and right epididymis.

The efferent ductulus transport sperm to the epididymis.

•Long duct surrounded by connective tissue.

•12‐15 feet in length!

•Stores sperm until they are fully mature and motile.

•Resorbs old sperm that are not released.

Describe the structure and function of the left and right ductus deferens.

Ductus Deferens (Vas Deferens)

•thick‐walled, muscular tubes inside the spermatic cords

•muscular layer contracts to propel sperm forward.

•extend through the inguinal canal and into the pelvic cavity

•wrap around the top of the bladder to the posterior side and widen into ampullae

•merge with the seminal vesicles to form ejaculatory ducts.

Describe the structure and function of the ejaculatory ducts.

Ejaculatory Ducts

•Short tubes that connect the ampullae of the left and right ductus deferens to the prostatic urethra.

•Receive fluids from the seminal vesicles that are major components of semen.

•Seminal vesicle fluids combine with sperm inside the ejaculatory ducts

Describe the function of the urethra.

Urethra

•Transports semen from the ejaculatory ducts to the outside of the body.

•Recall the three sections: prostatic, membranous, and spongy.

•Ends at the external urethral orifice.

Describe the contents of semen, and the purpose of key components.

Semen – seminal fluids produced by the male accessory glands plus sperm that have traveled from the testes to the ejaculatory ducts.

•call ejaculate when released from the body through ejaculation.

•seminal fluids make up the vast majority of the volume.

•seminal fluids contain alkaline buffers to neutralize the acidity along the vaginal lining and nutrients to provide sperm with energy.

•secreted from the seminal vesicles, the prostate, and the bulbourethral glands.

•takes about two weeks for a sperm cell to travel from a testis to become part of an ejaculate.

Describe the function of the seminal vesicles and the components they secrete into semen.

seminal vesicles: paired glands on the posterior side of the bladder

secrete a thick, whitish‐yellow, alkaline fluid with these components/features:

•Alkaline pH helps protect sperm from acidity of the vaginal lining

•Fructose – nutrients for energy

•Prostaglandins – chemical signals that trigger widening of the external os of the cervix and smooth muscle contraction of the uterus

Describe the function of the prostate gland and the components it secretes into semen.

prostate gland: single gland inferior to the bladder, contains numerous small gland structures that secrete fluids into the prostatic urethra.

Secretes a slightly milky fluid containing:

•Citric Acid – energy source

•Prostate‐Specific Antigen (PSA) – enzyme that helps liquefy semen following ejaculation (levels measured in blood work to check for prostate cancer)

•Seminal plasmin – antibacterial chemical that inhibits urinary tract infections

Describe the function of the bulbourethral gland secretions.

bulbourethral gland: small, paired glands located within the muscular wall of the pelvis next to the membranous urethra.

•ducts from these glands pass through the bulb of the penis and open into the spongy urethra.

•secrete a clear, thick mucus that coats and lubricates the urethra for passage of sperm

Describe the problems associated with benign prostatic hyperplasia and prostate cancer.

Benign Prostatic Hyperplasia (BPH):

•Noncancerous enlargement of the prostate

•Common in older men

•Growths can compress the prostatic urethra → problems with urination

Prostate Cancer

•One of the most common cancers in men over 50

•Often asymptomatic early

•Detected through digital rectal exams and Prostate Specific Antigen (PSA) blood tests

Describe the structure of the penis and the basic functions of its parts. Consists of internal and external parts

Internal parts: Root = internal portions, composed of the: Bulb – attached to the bulbospongiosus muscle, Crus (crura = plural) – two “wings” extending laterally, attach to the pubic arch

External parts: Body (shaft), Glans – tip of the penis with the external urethral orifice, Covered in the prepuce (foreskin) on an uncircumcised male.

three cylindrical erectile tissue structures inside the body/shaft of the penis:

•two paired corpora cavernosa (corpus cavernosum is singular), one corpus spongiosum, through which the urethra passes

•tunica albuginea – connective tissue covering around the erectile tissues and makes a connection with the skin

•blood vessels and nerves inside the shaft

Describe the male sexual response.

•Erectile tissues in the penis are venous spaces surrounding a central artery.

•During sexual arousal, blood fills the venous spaces, leading to an erection. The veins that drain the venous spaces are compressed, so the penis remains erect. Requires parasympathetic stimulation and release of nitric oxide (vasodilator)

•Semen is expelled during orgasm.

•Oxytocin release triggers smooth muscle contractions.

•Ductus deferens contract and propel sperm forward.

•Other ducts also contract.

•Accessory glands secrete their fluids → combine with sperm to form semen.

•Internal urethral sphincter contracts to prevent urine from combining with semen.

•Ejaculation – semen is expelled as smooth muscle in the wall of the urethra contracts rhythmically. (Requires sympathetic stimulation)

•Refractory period – after orgasm, period of minutes to hours or more when a male cannot have another erection.

Recall the examples of behavioral, barrier, and chemical contraception and how they prevent pregnancy.

contraception: methods of birth control/prevention of pregnancy, some methods are behavioral:

Abstinence – no sexual intercourse; only 100% effective method

Rhythm Method – avoiding sexual intercourse around the time of ovulation (a few days prior and after); high failure rate

Withdrawal Method – male withdraws penis before ejaculation; high failure rate as secretions before ejaculation may contain sperm

Lactation – production of milk and nursing (frequent lactation causes a reduction in FSH/LH levels; inhibits ovarian cycle, not very reliable; another method of contraception needs to be used)

Intrauterine Devices (IUD’s) – T‐shaped devices inserted into the uterus by a healthcare provider. Prevents fertilization from occurring (mechanism not understood) May contain copper or synthetic progesterone. Last several years. Low failure rates

Recall the examples of chemical contraception and how they prevent pregnancy.

Oral contraceptive pills – typically 28‐day packets

•pills taken during days 1‐21 contain low levels of estrogen and progestins, prevent the LH spike needed for ovulation, days 22‐28 = sugar pills; allow menstruation to occur, menstrual periods typically lighter as uterine lining does not develop as thickly, failure rate only 0.1% if used correctly

Estrogen/progestin patches – deliver hormones through the skin; replaced weekly

Injected/implanted progestins – prevent ovulation and maintain thick cervical mucus as a barrier to sperm entry; failure rate about 0.3%

Morning‐After Pills (Preven, Plan B, One‐Step) – taken within 72 hours of intercourse; inhibit ovulation or delay ovulation and/or irritate the uterine lining and prevent implantation

Mifepristone (Mifeprex or RU‐486) – can be used during the first seven weeks of pregnancy; blocks progesterone receptors → progesterone cannot bind to the uterine wall → induces miscarriage

Describe the surgical methods of contraception in females and males, and compare them for effectiveness and risk.

Tubal ligation in females:

•Both uterine tubes are cut, and the ends are tied or cauterized.

•Prevents sperm from reaching the oocyte, and the oocyte can’t reach the uterus.

•More invasive than a vasectomy.

Vasectomy in males:

•Can be performed outpatient.

•Each ductus deferens is cut, and a short segment is removed.

•Ends are tied off.

•Sperm can’t make it past the cut points and are eventually phagocytosed

Recall the examples of sexually transmitted infections.

Genital Herpes: caused by herpes simplex viruses (type 1 or type 2), cyclic outbreaks of blisters containing infectious fluid, virus remains dormant inside sensory neurons, and new outbreaks occur, antiviral medications lessen severity

Gonorrhea: caused by a bacterial organism, can be transferred from mother to newborn at delivery (can be life‐threatening). can lead to PID in women or epididymitis in men, treatable by antibiotics, but antibiotic‐resistant strains are emerging

Syphilis: caused by a bacterial organism, characterized by a sore called a chancre that contains the bacteria, can be passed across the placenta, causing severe problems or death to the newborn, treatable with antibiotics, if untreated, persists for years and goes through different stages, ultimately affecting the brain

HIV/AIDS: recall from the immune system chapter, kills Helper T‐Cells, poor immune function leads to numerous infections with other microorganisms, can be controlled with several antiviral drugs, but no cure

Distinguish between genotypic and phenotypic sex.

Genetic Sex (genotypic sex) – sex of an individual based on the sex chromosomes inherited and determined at fertilization:

• XX = female

• XY = male

Phenotypic Sex – based on appearance of the internal and external genitalia

• Ovaries plus female external genitalia – female

• Testes plus male external genitalia – male

Male and female reproductive organs develop from the same structures in an embryo

Recall how expression of the SRY gene on the Y chromosome determines phenotypic sex.

The Y chromosome has a gene (Sex‐Determining Region Y, or SRY gene)

•codes for proteins that stimulate production of androgens in the embryo → male phenotype develops

•If no Y chromosome or the SRY gene is abnormal → female phenotype develops

Define intersex conditions.

Intersex Conditions – genotypic sex (XY) doesn’t match phenotypic (genitalia)

True Gonadal Intersex – individual with both ovarian and testicular structures and ambiguous (unclear) female genitalia; rare.

46 XY Intersex – genetic male, but external genitalia appear female

•usually caused by androgen insensitivity syndrome: body’s cells don’t respond to androgen due to lack of receptors or non‐functional receptors.

•can also be caused by lack of testosterone during development.

46 XX Intersex – genetic female with external genitalia that appear male

•enlarged clitoris looks like a penis and the labia majora may partially fuse and look like a scrotum.

•can occur if the mother was exposed to excessive androgens during pregnancy or if the fetus’ adrenal glands overproduce androgens.

Explain how puberty is triggered.

•Period in adolescence when reproductive organs become fully functional.

•External/secondary sex characteristics become more prominent.

•Initiated with GnRH secretion → FSH and LH from the anterior pituitary  sex hormone production and gametogenesis.

•Earliest signs are breast bud development in females and axillary and public hair development in both sexes.

•Menarche (first menstrual period) in girls usually occurs about two years after puberty onset.

•Girls generally reach puberty about two years earlier than boys: 8‐12 for girls and 9‐14 for boys

Recall the characteristics of menopause and male climacteric.

Menopause in females usually occurs between ages 45‐55.

•no monthly periods for one year.

•sex hormone levels drop dramatically as follicles stop maturing.

•some atrophy of the breasts and reproductive organs.

•hot flashes can occur, thinning hair, increased risk for osteoporosis and heart disease.

•hormone Replacement Therapy – estrogen and progesterone replacement was prescribed more so in the past, but has been associated with increased breast cancer risk.

Male Climacteric

•testosterone levels drop in most men in their 50’s, but not as dramatic of a drop as in females (decline is more gradual).

•usually few symptoms

•can have mood swings, decreased sex drive, hot flashes, and sweating

•aging men may experience prostate enlargement and/or erectile dysfunction.

•vasodilator drugs, such as Viagra, work by prolonging dilation of the penile arteries

•not recommended for men taking vasodilators (nitrates) for chest pain due to risk of hypotension.

Recall the stages of the prenatal period.

Begins with fertilization of a secondary oocyte by a sperm.

Ends approximately 38 weeks later with birth.

•note: pregnancies are dated from the start of the last menstrual period, which is approximately two‐weeks before ovulation and fertilization. So a typical pregnancy = 40 weeks.

Divided into three shorter periods (first two periods collectively called embryogenesis):

•Pre‐embryonic period – first two weeks of development

•Embryonic period – Weeks 3 to 8 of development

•Fetal period – Weeks 9 to 38

Describe the steps of fertilization, including completion of meiosis by the secondary oocyte.

•Sperm penetrates the secondary oocyte, usually in the ampulla part of the uterine tube.

•Secondary oocyte is viable for approximately 24 hours after ovulation. Sperm are viable for 3‐4 days after ejaculation

•Combines maternal and paternal genetic material to create the first diploid cell of the offspring. Determines the genotypic sex of the offspring. Begins the process of cleavage.

•Sperm undergo capacitation after ejaculation and before fertilization: Glycoprotein coat and some proteins are removed from membrane covering the acrosome.

•Out of the millions of sperm ejaculated, only a few hundred make it to the secondary oocyte.

•Secondary oocyte and surrounding cells secrete chemical signals that attract sperm. Typically only one sperm penetrates the secondary oocyte.

Corona Radiata Penetration: Motility of sperm allows them to push through the cells and reach the zona pellucida.

Zona Pellucida Penetration: Acrosomes release digestive enzymes to penetrate. When one sperm penetrates and its nucleus enters the secondary oocyte → zona pellucida hardens to prevent additional sperm from fertilizing. Polyspermy, if it occurs, is fatal to the fertilized oocyte.

Recall the basic steps of development after fertilization through implantation, including the structure of the blastocyst.

•Fusion of Sperm and Oocyte Plasma Membranes and Fusion of Sperm and Ovum Pronuclei: Sperm and oocyte plasma membranes fuse when they make contact.

•Nucleus of the sperm (with 23 chromosomes) enters the secondary oocyte. The secondary oocyte completes Meiosis II, forming an ovum and polar body.

•Nucleus of the ovum now has 23 single chromosomes.

•Pronuclei of the sperm and ovum fuse to create the nucleus of the zygote (diploid with 46 chromosomes).

Cleavage: Mitotic cell divisions that increase number of cells, but not overall size of the pre‐ embryo. Remains the same size until it implants in the uterus.

•The morula stage enters the lumen of the uterus; fluid leaks inside, creating a fluid‐ filled cavity.

•Pre‐embryo at this stage with the cavity is called a blastocyst

Define pluripotent stem cell, and recall where these cells are located in a blastocyst.

Embryoblast (inner cell mass) – will go on to form the embryo.

•Cells are pluripotent – have the potential to develop into differentiate into any cell or tissue type in the body.

Recall the location of implantation and the role of the trophoblast.

•Process by which the blastocyst burrows into and embeds within the endometrium.

•Trophoblast divides into two layers and burrows into the endometrium, bringing along the rest of the blastocyst. Trophoblast – outer ring of cells surrounding the blastocyst cavity (Will later form the chorion)

•By day 9, blastocyst has completely burrowed into the uterine wall. Starts receiving nutrients from uterine glands.

•Outer part of the trophoblast starts producing human chorionic gonadotropin (hCG).

Describe the secretion of human chorionic gonadotropin, and explain its role in maintaining an early pregnancy.

•hCG signals the corpus luteum to stay alive and keep producing progesterone and estrogen.

•Uterine lining continues to thicken and is maintained; no menstrual period.

•hCG levels remain high for the first three months of pregnancy.

•Corpus luteum degenerates when hCG levels decline, but the placenta has taken over production of progesterone and estrogen.

•hCG is the hormone detected in pregnancy tests.

Describe the three extraembryonic membranes.

Extraembryonic Membranes – form from the disc and trophoblast.

Yolk sac: forms from the hypoblast, early site of blood cell and blood vessel formation, does not contain yolk as in birds

Amnion: forms from the epiblast, eventually encloses entire embryo and forms fluid‐filled amniotic cavity

Chorion: derived from the trophoblast, combines with endometrial tissues to form the placenta

Describe the structure and function of the placenta.

•Connection between the embryo‐fetus and the mother (connecting stalk in the early embryo develops into an umbilical cord. Contains umbilical arteries (deoxygenated) and veins(oxygenated) that will bring blood to and from the placenta)

•Chorionic villi form from the chorion and contain branches of the umbilical blood vessels. Project into the endometrium.

•Exchanges nutrients, respiratory gases, and waste products between the maternal and embryonic/fetal blood.

•Allows passage of antibodies from the mother’s blood to the blood of the embryo/fetus

•Produces estrogen and progesterone to maintain and build the uterine lining (takes over for the corpus luteum in the ovary).

•Compartments develop in the functional layer of the endometrium and fill with maternal blood.

•Maternal blood and embryonic/fetal blood do not make physical contact, but barrier between them is thin enough for exchanges.

•Barrier is selectively permeable (most microorganisms cannot cross from mother to embryo/fetus, but some pathogens can, high levels of maternal hormones do not cross, drugs, alcohols, toxins can cross)

•Begins to develop during pre‐embryonic period, but most growth occurs during the fetal period.

Name the three primary germ layers, and recall the major body structures derived from them as the embryo develops.

Ectoderm – mainly forms the skin epidermis, nervous system, and associated structures

Mesoderm – forms many internal structures: muscles, bones, connective tissues, heart, kidneys, internal reproductive organs, spleen, inner epithelial linings of blood vessels, lymphatic vessels, and serous membranes

Endoderm – inner epithelial (mucosal) linings of the respiratory tract, urinary tract, reproductive tract, and digestive tract; also forms some accessory digestive organs

Recall when organogenesis occurs, and explain the possible effects of teratogens.

By Week 8, early forms of most organ systems have developed and the limbs have developed their adult shapes.

Teratogens – substances that can cause birth defects or death of the embryo (alcohol, tobacco smoke, drugs, some microorganisms, toxic chemicals)

The organogenesis period is the most sensitive to teratogens since all body systems develop.

•peak development periods vary for different systems, so timing of teratogen exposure determines which body systems are damaged.

Recall the major events of the fetal period and when it occurs.

•week 9 of development to birth

•maturation of tissues and organs

•rapid growth of the fetus

•weight increase is most dramatic during the final two months.

•a mature fetus weighs 5.5 to 9.9 pounds.

Recall the timing and key events of the three trimesters of pregnancy.

First Trimester: first three months of pregnancy

•first 12 weeks of development of the embryo/fetus

•embryonic period plus first part of the fetal period

•keep in mind that pregnancies are dated starting with the first date of the last menstrual period, so conception of the zygote actually occurs two weeks later.

•a typical 40‐week pregnancy includes 38 weeks of development from conception onward.

Second Trimester: months 4 to 6

•growth of the fetus plus expansion of maternal tissues

Third Trimester: months 7 to 9

•rapid fetal growth and weight gain

•mother’s body prepares for labor and delivery

Recall the key functions of the various hormones secreted during pregnancy.

hCG levels remain high during the first trimester: signals the corpus luteum to stay alive and secrete progesterone and estrogen (maintains uterine lining and prevents miscarriage).

placenta takes over progesterone and estrogen production for the rest of the pregnancy, so the corpus luteum is no longer needed. High levels of progesterone and estrogen from the placenta:

•suppress FSH and LH from the anterior pituitary (prevents ovarian follicle development and ovulation)

•progesterone stimulates endometrial growth and suppresses menstruation

•stimulate uterus and mammary gland enlargement

•stimulate fetal growth

•fuller, thicker hair and stronger nails

•relaxation of ligaments and joints in the pelvis (sacroiliac joints and the pubic symphysis)

Recall the key functions of the various hormones secreted during pregnancy.

Relaxin – secreted by the corpus luteum and placenta; promotes blood vessel growth in the uterus; does not appear to stimulate joint/ligament relaxation in spite of name

Corticotropin‐Releasing Hormone (CRH) – placenta secretes in much larger amounts than the hypothalamus

•thought to regulate length of pregnancy and timing of childbirth

•triggers increased aldosterone production  increased fluid retention, blood volume, and blood pressure (can lead to edema)

Human Chorionic Thyrotropin (HCT) – stimulates thyroid hormone secretion like TSH; increases metabolic rate

Human Placental Lactogen (HPL) – name suggests affects lactation, but not proven; stimulates increased use of fatty acids for energy by the mother, reserving glucose for the fetus; inhibits insulin

Recall the major effects of pregnancy on the functions of the different body systems.

dramatic changes to the uterus during pregnancy: smooth muscle layer cells expand in size and tissue grows, expansion of the uterus detectable at 4 weeks post‐conception, by the ninth month, the fundus is at the level of the xiphoid process: compression of the diaphragm and abdominopelvic organs affects breathing, digestion, and urination

mammary glands: tender and sore due to estrogen and progesterone. Melanocyte‐Stimulating Hormone (MSH) from the placenta triggers darkening of the areola and the linea nigra on the abdomen, mammary gland tissues grow

digestive system, nutrient, and metabolic: Human Placental Lactogen – triggers mother to use more fatty acids for energy, leaving more glucose for the fetus. High levels of HPL, estrogen, progesterone, and CRH increase insulin resistance (spares glucose for the fetus, can trigger gestational diabetes mellitus). Morning Sickness – mostly during the first trimester; nausea, some vomiting (sometimes more severe) (could be caused by hCG, but not proven)

•progesterone – relaxes smooth muscle, which slows digestive motility; heartburn and indigestion can occur, especially later in pregnancy; constipation

•mom needs about 300 more calories each day to supply herself and the developing fetus (folic acid, iron, calcium, and protein are very important)

Recall the major effects of pregnancy on the functions of the different body systems.

The cardiovascular system of the mother has to distribute oxygen and nutrients to both the mother and fetus.

•plasma volume increases by about 50%.

•cardiac output increases 30‐50% beginning at Week 6 and peaks at Weeks 24‐28 (both heart rate and stroke volume increase)

•blood viscosity drops because of increased plasma volume, which helps prevent hypertension despite high cardiac output.

•venous return from the lower body is impaired by the third trimester because the fetus compresses abdominal blood vessels.

Shortness of breath may occur as the diaphragm cannot fully flatten out  decreased inspiratory volumes (oxygen consumption increases 20‐30% to meet the demands of both mother and fetus)

progesterone causes central chemoreceptors to become more sensitive to CO2 . More CO2 is expelled by increasing tidal volume. This lowers CO2 in the mother’s blood and makes it easier for CO2 to diffuse across the placenta from fetus to mother.

Urinary System Changes: GFR increases by 30‐50% because of excess plasma volume and the need to filter out wastes from both mother and fetus. Expanding uterus compresses the bladder → frequent urination. Progesterone triggers smooth muscle relaxation → expands the ureters → slows flow of urine from the kidneys to the bladder. Compression of the ureters or kidneys by the uterus can also reduce urine drainage. Increases risk of urinary tract infections

Distinguish between false and true labor.

False labor: Braxton‐Hicks contractions occur, but are generally weak and irregularly spaced; do not cause the cervical changes of labor

True labor = uterine contractions that increase in frequency and intensity and result in cervical changes

Describe the events of the positive feedback processes of true labor.

•Hypothalamus (in both mother and fetus) triggers the posterior pituitary to secrete increased oxytocin.

•Oxytocin triggers the placenta to secrete prostaglandins  soften and dilate the cervix.

•Oxytocin and prostaglandins stimulate uterine contractions.

•Fetal head pushes on the cervix → nerve signals sent to the hypothalamus  more oxytocin released (positive feedback)

Describe the stages of true labor.

Dilation Stage: Begins with onset of regular uterine contractions. Ends when the cervix is effaced (thinned) and fully dilated to 10 cm in diameter. Dilation and effacement occur as the fetus’ head is pushed against the cervix. Amniotic sac ruptures and releases amniotic fluid.

Expulsion Stage: Begins with the complete dilation of the cervix. Normally takes thirty minutes to several hours. Uterine contractions and Valsalva maneuver by the mother help push the fetus through the vagina. Episiotomy – skin and muscles of the perineum are cut to make a wider opening if the head won’t deliver easily

Placental Stage: After the baby is expelled. Uterus continues to contract → compresses uterine blood vessels. Placenta detaches from the uterine wall. Placenta plus remaining amnion = afterbirth. Usually expelled within thirty minutes after the baby.

Recall the key respiratory and cardiovascular changes that occur quickly after birth.

respiratory changes: the newborn is known as a neonate.

•first breath usually taken within about 10 seconds after birth.

•thought to be triggered by the central nervous system responding to changes in temperature and environment and/or the buildup of carbon dioxide leading to acidosis.

•lungs inflate with the first breath; surfactant keeps the alveoli open.

•premature infants born before 28 weeks may not have enough surfactant to keep their alveoli open and may require a ventilator.

cardiovascular changes: The foramen ovale in the heart and the ductus arteriosus passage between the aortic arch and the pulmonary arteries close.

•pulmonary arteries dilate for the pulmonary circulation.

•the umbilical vein and arteries constrict and become nonfunctional (transition into ligaments).

•the ductus venosus that connects the umbilical vein to the inferior vena cava also becomes a ligament.

Recall the hormonal changes in the mother after birth and their key effects.

•Estrogen and progesterone levels drop rapidly after giving birth (may be responsible for “baby blues.”)

•Hair loss may occur (suppressed during pregnancy).

•Respiratory rate and depth return to normal since progesterone is no longer making the central chemoreceptors more sensitive to carbon dioxide.

•CRH levels drop dramatically without the placenta producing high amounts (high levels of CRH during pregnancy may be associated with postpartum depression)

Recall how fluid levels return to normal in the mother after birth.

•Excess blood volume no longer needed and must be expelled.

•Some is expelled with endometrial tissue released after delivery (heavy menstrual‐like flow as very thick endometrial lining is shed).

•Increased urination may occur as aldosterone levels drop due to the decline in CRH.

•Excess tissue fluids are cycled through lymphatics to the blood for filtration in the kidneys and release in the urine.

•Profuse sweating may also occur, which helps release excess fluid.

Describe the lactation process and benefits for the mother and newborn.

lactation: production and release of milk from the mammary glands.

•Prolactin from the anterior pituitary stimulates milk production. Estrogen stimulates increased prolactin secretion.

•During late pregnancy and the first few days after birth, colostrum is secreted by the mammary glands before the true milk (rich in antibodies, especially the IgA type → passive immunity for the infant)

•Positive feedback mechanism for production and release of milk.

•Infant suckling → nerve signals sent to the hypothalamus.

•Hypothalamus triggers release of oxytocin → targets contraction of cells in the mammary glands that squeeze milk toward the nipple (milk letdown).

•Suckling inhibits the release of Prolactin‐Inhibiting Hormone, so the anterior pituitary releases more Prolactin → increases milk production → new supply of milk available for the next feeding.

•Many women do not ovulate while breastfeeding, probably due to suppression of GnRH; however, this is not a reliable form of birth control.

Recall how the uterus returns to normal size after delivery.

•The uterus takes 6 weeks following birth to return to being close to its pre‐ pregnancy size.

•Oxytocin helps the shrinkage by stimulating uterine contractions (afterpains).

•Afterpains may be more severe and noticeable during breastfeeding.

•The return to pre‐pregnancy size may occur more slowly in women who do not breastfeed.