Exam 4 pt. 3 Flashcards
Define gonad. Define gamete. What is the male sex hormone? The female?
o Function: production of offspring
o Significant anatomical differences between male and female systems
o Reproductive systems “slumber” until puberty
o Gonads: primary sex organs
Males: testes; Females: ovaries
o Gametes: sex or reproductive cells made in the gonads
Males: sperm; Females: ova/egg
o Sex Hormones
Males: androgens; Females: estrogens and progesterone
o Accessory Reproductive Organs: ducts, glands, and external genitalia
Define gonad
o Gonads: primary sex organs
Males: testes; Females: ovaries
Define gamete
o Gametes: sex or reproductive cells made in the gonads
Males: sperm; Females: ova/egg
What is the male sex hormone? The female?
Males: androgens; Females: estrogens and progesterone
- Memorize the path of sperm from seminiferous tubule to external body surface.
What are the two muscles of the scrotum? How do these muscles move the testes?
o Dartos: smooth muscle; wrinkles scrotal skin; pulls scrotum close to the body
o Cremaster: skeletal muscle; bands of muscle that elevate the testes
What is the purpose of the testes being outside the abdominopelvic cavity?
o Sac of skin and superficial fascia; contains paired testes
o Hangs outside the body’s abdominopelvic cavity
o Midline septum divides the scrotum into 2 compartments – 1 for each testis
o Maintains a temperature about 3°C cooler than body temperature
Define the two tunics of the testes.
o Tunica Vaginalis: outer layer, derived from peritoneum
o Tunica Albuginea: inner layer; forms fibrous capsule
o Septa extending inward from the tunica albuginea divide each testis into ~250 wedge-shaped lobules
o Each lobule contains 1 to 4 tightly-coiled seminiferous tubules
What is a sustentocyte? What are they supporting?
What is made by the interstitial endocrine cells in the testes?
o Interstitial cells produce androgens, such as testosterone, and secrete them into the interstitial fluid
What is the functional importance of the pampiniform venous plexuses?
o Testicular veins arise from the pampiniform venous plexuses surrounding each testicular artery
o Cooler blood in the venous plexus absorbs heat from the testicular arteries and keeps the testes cool
o Both divisions of the autonomic nervous system serve the testes
What is carried in the spermatic cord?
o Spermatic Cord: encloses the autonomic nerve fibers, blood vessels, vas deferens, and lymphatic vessels that supply the testes
o Spermatic cord travels through the inguinal canal
What are the 3 parts of the penis?
o Penis: male copulatory organ
o External Genitalia: scrotum + penis
o Anatomy of the Penis
Root + shaft + glans penis
Prepuce (Foreskin): cuff of loose skin covering the glans
Define circumcision
o Circumcision: surgical removal of the foreskin
~60% of males in the US are circumcised, less common in other parts of the world
Circumcision can lead to a reduction in the risk of contracting HIV or other reproductive infections
Be prepared to locate corpus spongiosum and corpus cavernosum in a picture. Which cylindrical body makes up the glans penis?
o Internally, the penis is made of the spongy urethra and 3 long cylindrical bodies of erectile tissue
o Each cylindrical body is covered by a sheath of dense, fibrous connective tissue
o Erectile tissue is a spongy network of connective tissue and smooth muscle riddled with vascular spaces
o Corpus Spongiosum: surrounds the spongy urethra and expands to form the glans penis
o Corpus Cavernosa: paired dorsal erectile bodies
o Erection: erectile tissue fills with blood; penis enlarges, becomes rigid
During an erection, the vascular spaces in erectile tissue fill with blood
What is the function of the epididymis? How long do sperm cells typically remain in the epididymis?
o Epididymis: site of sperm maturation
o Nonmotile, immature sperm enter the epididymis and pass slowly through it over ~20 days
o Sperm can be stored for several months
o Head: contains efferent ductules, located on the superior aspect of the testis
o Body and Tail: located on the posterolateral area of the testis
o Duct of the Epididymis: 20 feet of highly-coiled duct, lined with microvilli to absorb testicular fluid and pass nutrients to stored/maturing sperm
o During ejaculation, the epididymis contracts and expels sperm into the ductus/vas deferens
The vas deferens merges with a duct from what gland to form the ejaculatory duct?
o Passes through the pelvic cavity
o Lined with smooth muscle that propels sperm from epididymis to urethra
o Expands to form the ampulla
o Joins the duct of the seminal vesicle to form the ejaculatory duct
Be able to explain why a vasectomy is an effective form of birth control.
o Vasectomy: cutting and ligating the vas deferens
Reversible; nearly 100% effective form of birth control
List the three portions of the male urethra from proximal to distal.
o Prostatic: surrounded by the prostate gland
o Intermediate/Membranous: in the urogenital diaphragm
o Spongy: runs through the penis; opens at external urethral orifice
What is contained in the secretions made in the seminal vesicles/glands? How about from the prostate gland?
o Seminal gland
Lie on the bladder’s posterior surface
Contain smooth muscle that contracts during ejaculation
The duct of each seminal gland joins the ducts of the vas deferens to form the ejaculatory duct
The secretions of the seminal glands – viscous, alkaline seminal fluid - account for 70% of the volume of semen
Seminal fluid contains fructose, citric acid, coagulating enzyme (vesiculase), and prostaglandins
Yellow pigment of seminal fluid fluoresces with UV light
o Prostate Gland
Encircles the urethra inferior to the bladder
Size of a peach pit
Consists of smooth muscle that contracts during ejaculation
Secretes milky, slightly acid fluid that contains citrate, enzymes, and prostate-specific antigen (PSA)
Prostatic fluid plays a role in sperm activation and makes up ~1/3 of the volume of semen
Define BPH. What’s a TURP procedure?
o Benign Prostatic Hyperplasia (BPH): benign growth of the prostate that constricts the urethra and makes urination difficult
o Incomplete bladder emptying can lead to frequent UTIs and kidney damage
o TURP: surgical procedure to widen the prostatic urethra
o Affects 50% of men at age 50, 80% of men at age 70
o Prostatitis: acute or chronic inflammation of the prostate, may or may not be related to infection
What is the functional importance of the secretions from the bulbourethral glands?
o Pea-sized glands inferior to the prostate
o Produce thick, clear mucus during sexual arousal
o Mucus lubricates the glans penis and neutralizes any traces of acidic urine in the urethra
About how many sperm cells are in a typical ejaculation (a general range)?
o Milky white mixture of sperm plus the secretions of all the accessory glands
o 2-5mL of semen is ejaculated. It contains 20-150 million sperm/mL.
o Glandular secretions protect and activate sperm, facilitate their movement, and contain fructose for producing ATP
o Alkaline nature of semen will neutralize the acidity of the male urethra and the female vagina
What is the function of prostaglandins in semen? How about relaxin? What about clotting factors and fibrinolysin?
o Contains prostaglandins to decrease the viscosity of mucus in the female cervix and stimulate reverse peristalsis in the female uterus
o Contains the hormone relaxin + other enzymes to enhance sperm motility and suppress female immune response
o Contains ATP for energy and antibiotics to destroy bacteria
o Contains clotting factors to coagulate semen initially and then fibrinolysin to liquify it
What branch of the ANS is responsible for the formation of an erection? Which branch is responsible for ejaculation?
o Erection: enlargement and stiffening of the penis
o Arterioles are normally constricted – excitement causes activation of parasympathetic neurons and release of Nitric Oxide (NO)
o Arterioles dilate with relaxation of smooth muscles
o Corpora cavernosa expands and retards venous drainage – erectile tissues become engorged
o Propulsion and expulsion of semen from the male duct system
o Sympathetic Spinal Reflex
Bladder’s internal sphincter muscle constricts to prevent expulsion of urine or reflux of semen
Ducts and accessory glands contract, empty their contents into the prostatic urethra
Bulbospongiosus muscles undergo a series of very rapid contractions that cause expulsion of semen
Ejaculatory event is called orgasm
o Erectile Dysfunction
Exists in ~50% of men over age 40
Causes: psychological factors, alcohol, medications (antihypertensives, antidepressants), blood vessel impairment, nerve damage
Sildenafil (Viagra) contains NO
Review the basics of genetics – define haploid, diploid, chromosome numbers, mitosis, meiosis.
o Spermatogenesis: creation of sperm in the seminiferous tubules
o Most human body cells have 46 chromosomes arranged in 23 pairs
Each pair of chromosomes = homologous chromosomes
Each pair contains1 maternal and 1 paternal chromosome
Diploid Cell: a cell with 46 chromosomes (2n)
o Gametes only have 23 chromosomes
Only one half of each homologous pair
Haploid Cell: a cell with 23 chromosomes (n)
o Gamete formation involves meiosis – different from mitosis!
o Mitosis involves 1 replication event and 1 division event – it produces 2 identical daughter cells
o Meiosis involves 1 replication event and 2 division events – it cuts the number of chromosomes in half and produces 4 genetically diverse daughter cells
Outline the 3 steps of spermatogenesis (slide 28).
o Occurs in the seminiferous tubules of the testis
o Begins around age 14 and continues throughout life
o About 90 million sperm are made per day
o Spermatogenic cells give rise to spermatozoa (sperm)
o Basic Overview: 3 Steps
Mitosis of Spermatogonia (Stem Cell) – forms 1 stem cell and 1 primary spermatocyte
Meiosis – primary spermatocytes form secondary spermatocytes, which become spermatids
Spermiogenesis – spermatids become spermatozoa (immature sperm)
Define spermatogonia. What is the net result of mitosis of spermatogonia.
o Mitosis of Spermatogonia (Stem Cell) – forms 1 stem cell and 1 primary spermatocyte
Spermatogonia: stem cells in contact with epithelial basal lamina
Each mitotic division yields 1 type A daughter cell and 1 type B daughter cell
* Type A daughter cells maintain the germ/stem cell line
* Type B daughter cells move toward the lumen and develop into primary spermatocytes
What is the net result of meiosis I and meiosis II?
o Meiosis: spermatocytes to spermatids
Meiosis I: primary spermatocyte (2n) undergoes meiosis I forming two secondary spermatocytes (n)
Meiosis II: each secondary spermatocyte (n) rapidly undergoes meiosis II to become two spermatids (n)
o Spermatid: small, nonmotile; found close to the tubule’s lumen
What happens during spermiogenesis?
o Spermiogenesis: spermatids to immature sperm
Spermatids have the correct haploid chromosome number for fertilization, but they are nonmotile
Spermiogenesis: streamlining process where each spermatid elongates, loses excess cytoplasm, and forms a tail – becomes a spermatozoa (sperm)
Be prepared to label the parts of a mature sperm cell.
o Three Major Regions
Head: genetic region; includes the nucleus and a helmetlike covering called the acrosome
Acrosome contains hydrolytic enzymes that enable sperm to penetrate an egg
Midpiece: metabolic region containing mitochondria – ATP is required to move the tail
Tail: locomotor region, includes flagellum
Draw/write out the sequence of hormones triggering the secretion of testosterone and spermatogenesis. “Gonadotropic releasing hormone is released from the hypothalamus……” and so on.
o Hypothalamic-Pituitary-Gonadal (HPG) Axis: production of gametes and sex hormones is regulated by a sequence of events involving the hypothalamus, anterior pituitary gland, and testes
o Involves interacting hormones: GnRH, FSH, LH, testosterone, and inhibin
o Hypothalamus releases gonadotropin-releasing hormone (GnRH)
o GnRH binds to anterior pituitary gonadotropic cells causing them to secrete:
Follicle-Stimulating Hormone (FSH)
Luteinizing Hormone (LH)
o FSH indirectly stimulates spermatogenesis by stimulating sustentocytes to release androgen-binding protein (ABP)
ABP promotes spermatogenesis by keeping the concentration of testosterone high near the spermatogenic cells
o LH binds to interstitial endocrine cells to secrete testosterone
o Testosterone entering the blood triggers sex organ maturation, development of secondary sex characteristics, and development of libido
o Rising testosterone levels feed back to hypothalamus to inhibit GnRH and to the pituitary to inhibit release of gonadotropins
o Inhibin: hormone released by sustentocytes when sperm count is high – inhibits the release of GnRH and FSH
Review the systemic effects of testosterone. Where else are androgens produced?
o The amount of testosterone and sperm produced by the testes reflects balance among different, interacting sets of hormones
o Balance takes ~3 years to achieve then testosterone and sperm production levels become relatively stable throughout life
o In the absence of GnRH and the gonadotropins, the testes atrophy and sperm + testosterone production ceases
o Before birth, a male fetus has testosterone levels that are 2/3 that of an adult male – levels will recede after birth and remain low until puberty
o Secondary Male Sex Characteristics:
o Appearance of pubic, axillary, chest, and facial hair
o Deepening of the voice
o Thickening of skin + increased oil production
o Bone growth + increased bone density
o Increase in skeletal muscle size and mass
o Increase in basal metabolic rate
o Testosterone is the basis of libido in males
o Testosterone has effects on the embryonic brain and continues it effects well into adulthood
o Androgens are also produced by the adrenal glands, but that is insufficient to maintain normal testosterone –mediated functions
