Chapter 28: The Reproductive System Flashcards
Gonads
Testes in males.
Produce and secrete sex hormones.
Ducts
Various ducts stores and transport gametes.
Accessory Sex Glands
Produce substances that protect gametes and facilitate movement.
Supporting Structures
Penis in males
Uterus in females
Assist in the delivery of gametes.
The uterus is also the site for growth of the embryo and fetus during delivery.
Male Reproductive System Organs
Include:
Testes: a system of ducts (epididymis, ductus deferens, ejaculatory ducts and urethra) produce sperm and secrete hormones. The duct systems transports and stories sperm, assist in their maturation and conveys them to the exterior.
Accessory sex glands: seminal vesicles, prostate and bulbourethral glands.
Several supporting structures: scrotum, penis
Scrotum
The supporting structure of the testes.
Consists of loose skin and underlying SC layer that hangs from the root of the penis.
The location of the scrotum and its contraction of its muscle fibers regulate the temperature of the testes.
Raphe
Median ridge that separates the scrotum porch into lateral portions.
Scrotal Septum
Internally this divides the scrotum into two compartments, each containing a single testis.
Dartos Muscle
Makes up the septum
Is made of SC layer and muscles tissue composed of smooth muscle fibers.
In response to cold temps this muscle will contract. This contraction causes the muscle to move closer to the body so it can absorb body heat.
This contraction causes the scrotum to become tight which reduces heat loss.
Cremaster Muscle
Associated with each testis in the scrotum.
Is a series of small bands of skeletal muscles that descends as an extension of the internal oblique muscle through the spermatic cord to surround the testes.
Normal Sperm Production
Requires a temp of 2-3 degrees below core body temp.
This lowered body temp is maintained within the scrotum because it is outside the pelvic cavity.
Testes
Or testicles, are paired oval glands in the scrotum measuring about 5 cm long and 2.5 cm in diameter.
Produce gametes and excrete sex hormones.
They develop near the kidneys in the posterior portion of the abdomen and begin their descend into the scrotum through the inguinal canals.
Tunica Vaginalis
Serous membrane
Is derived from the peritoneum and forms during the descent of the testes, partially covers the testes.
Hydrocele
A collection of serous fluid in the tunica vaginalis.
May be caused by injury to the testes or inflammation of the epididymis.
Usually no treatment is required.
Tunica Albuginea
White fibrous capsule composed of dense irregular CT that surrounds the testis.
Found internal to the tunica vaginalis.
Lobules
A series of internal compartments formed by the septa when the tunica albuginea extends inward.
Seminiferous Tubules
Tightly coiled tubules where sperm is produced.
Each of the 200-300 lobules contains one to three of these tubules.
Contains 2 types of cells:
1. Spermatogenic cells: sperm forming cells
2. Sustentacular cells: have several functions in supporting spermatogenesis.
Spermatogenesis
The process by which the seminiferous tubules of the testes produce sperm.
Takes 65-75 days
Process:
1. Spermatogonium (2n) stem cell- develop from primordial germ cells from yolk sac, enter the testes during the 5th week of develop. Undergo mitosis =
2. Primary spermatocyte (2n) 46 chromosomes
3. Secondary speratocyte (n) 23 chromosomes
Final Stage: Spermiogenesis:
4. Spermatid (n) 4 haploid cells (tetrad) from miosis II,
Creates:
5. Sperm cell or spermatozoon (n)-once form is released into the lumen of the seminiferous tubules.
Blood Testis Barrier
Tight junctions that are internal to the basement membrane and spermatogenia.
These tight junctions form the obstruction because substances must first pass through the Sustentacular cells before they reach the developing sperm.
Join neighboring Sustentacular cells to one another.
Interstitial Cells
Or Leydig cells
Found in spaces between adjacent seminiferous tubules.
Are clusters of cells.
These cells secrete testosterone and the most prevalent androgen.
Androgen
A hormone that promotes the development of masculine characteristics.
Primary Spermatocytes
Are dipoid (2n). Have 46 chromosomes.
Shortly after formed it replicated its DNA and meiosis begins.
Meiosis, hemologous pairs of chromosomes lines up at the metaphase plate and crossing over occurs.
Then meiosis spindle pulls one chromosome of each pair to an opposite pile of the dividing cell.
The 2 cells formed are called secondary spermatocytes.
Secondary Spermatocytes
2 cells formed by meiosis I. The meiotic spindle pulls one duplicated chromosome of each pair to an opposite pole of the dividing cell.
Each has 23 chromosomes, the haploid number (n).
Each chromosome within a secondary spermatocytes is made up of 2 chromatids still attached by a centromere. No replication of DNA occurs.
Spermatids
4 haploid cells resulting from meiosis II.
A single primary spermatocytes therefore produces 4 spermatids via 2 rounds of cell division: meiosis I and meiosis II.
Spermiogensis
The final stage of Spermatogenesis develops the haploid spermatids into sperm.
No cell division occurs here.
Each spermatids becomes a single sperm cell
Sperm
About 300 million sperm complete the process of Spermatogenesis. Only live up to 48 hours after ejaculated.
A sperm is about 60 um long.
Contains several structures that are highly adapted for reaching and penetrating a secondary oocyte.
Major parts:
1. Head: flatted, pointed about 4-5 um long. Contains a nucleus with 23 high;y condensed chromosomes. The nurses is covered by acrosome, a cap like vesicle filled with enzymes that help penetration.
2. Tail: subdivided into 4 parts. Neck: constricted region, contains centrioles. Middle part: contains mitochondria, provides ATP for locomotion. Principal piece: longest portion. End tail: the terminal, taping portion.
Gonadotropin Releasing Hormones (GNRH)
This hormones stimulates gonadotrophs in the anterior pituitary to increase their secretion of 2 gonadotropins.
Luteinizing Hormone
Stimulates interstitial cells located between seminiferous tubules to secret testosterone.
Is synthesized from cholesterol in the testes
Is the principal androgen.
Lipid soluble.
Follicle-Stimulating Hormone (FSH)
Acts indirectly to stimulate spermatogenesis.
FSH and testosterone act synergistically on the Sustentacular cells to stimulate the secretion of androgen-binding protein (ABP) into the lumen of seminiferous tubules and into interstitial fluid.
Inhibin
Released by Sustentacular cells once the degree of Spermatogenesis for male reproduction has been achieved.
Protein hormone used form inhibiting FSH secretion by the anterior pituitary.
Effects of Androgens
- Prenatal development: testosterone stimulates male patterns of development, decent of testes.
- Development of male sexual characteristics: testosterone and dihydrotestosterone bring about development and enlargement of male sex organs.
- Development of sexual function: contribute to male sexual behavior, Spermatogenesis and sex drive.
- Plays a role in muscular and skeletal growth
- Stimulation of anabolism: androgens are anabolic hormones. Stimulate protein synthesis.
Secondary Sex Characteristics
Traits that distinguish males and females but do not have a direct role in reproduction.
Ducts of the Testies
- Straight Tubules: very short ducts. Pressure generated by the fluid secreted by Sustentacular cells pushes sperm and fluid along the lumen of the seminiferous tubules into these short ducts. The straight tubules lead to:
- Rete testis: network of ducts in the testis. From here sperm move into:
- Efferent ducts: series of coiled ducts in the epididymis. These ducts empty into:
- Ductus Epididymis: single tube
Epididymis
Sperm mature here
Is an organ about 4 cm long that curves along the superior and posterior boarder of each testies.
Has a comma shape in profile.
Each consists of: tightly coiled ductus epididymis.
Head: where the efferent ducts join the ductus epidiymis.
Body: narrow mid portion
Tail: smaller inferior portion, continues to the ductus vascular deferens.
Stereocila
Contained on the free surface of columnar cells of the ductus epididymis.
Are long, branching microvilli that increase the surface area for the reabsorption of degenerated sperm.
Sperm Maturation
Happens at the epididymis.
Process by which sperm acquire motility and the ability to fertilize an ovum.
Occurs over period of 14 days.
Ductus Defernes
The tail of the epididymis where the ductus epididymis becomes less convoluted and diameter increases.
About 45 cm long. Conveys sperm during sexual arousal.
Ascends along the posterior boarder of the epididymis through the spermatic cord and enters the pelvic cavity.
Ampulla
Dilated portion of the ductus deferens.
Spermatic Cord
Supporting structure of the male repoductive system.
Ascends out of the scrotum.
Consists of: ductus deferens, testicular artery, autonomic nerves, lymphatic vessels and cremaster muscle.
Inguinal Canal
An oblique passageway in the anterior abdominal wall where the spermatic cord and ilioinguinal nerve pass through.
About 4-5 cm long.
Originates: deep inguinal ring-slit like opening in aponeurosis of transverse abdomis muslce
Ends: superficial inguinal ring- triangular opening in the aponeurosis of the external oblique muslce.
Varicocele
Refers to swelling in the scrotum due to a dilation of the veins that drain the testes.
Ejaculatory Ducts
Each duct is about 2 cm long.
Formed by the union of the duct from the seminal vesicle and the ampulla of the ductus defernes.
Terminate in the prostatic urethra where they eject sperm and seminal vesicles secretions.
Urethra
A shared terminal of the reproductive and urinary systems. Serves as a passage way for both semen and urine
About 20 cm long.
Passes through prostate, deep muscle of the perineum and penis.
Urethra: Subdivided into 3 Parts
- Prostatic urethra: long, passes through prostate. Duct continues inferiorly.
- Intermediate urethra: where the duct passes through the deep muscle of the perineum. About 1 cm long.
- Spongy Urethra: where the duct passes through the corpus spongiosum of the penis. About 15-20 cm long.
Ends at the external urethral orifice.
Seminal Vesicles
Paired, are convoluted pouch like structures.
About 5 cm long.
Lying posterior to the base of the urinary bladder and anterior to the rectum.
Secrete alkaline: viscous fluid that contains fructose, prostaglandins and clotting proteins. Helps neutralize the acid environment of the male urethra and female reproductive tract. Otherwise would kill sperm.
Prostate
Single, doughnut shaped gland about size of golf ball.
4 cm from side to side.
Inferior to urinary bladder and surrounds the prostatic urethra.
Prostate Secretions
Secretes a milky slight acidic fluid that contains several substances:
1. Citric acid: prostate fluid, used by sperm for ATP production via Krebs.
2. Proteolytic enzymes: PSA, pepsinogen, lysozyme, etc, breakdown the clotting proteins from the seminal vesicles.
3. Acid phosphates: secreted by the prostate, function unknown.
4. Seminal plasmin: prostatic fluid is an antibiotic that can destroy bacteria
Bulbourethral Glands
About the size of peas. Located inferior to the prostate on either side side of the membranous urethra within the deep muscle of the perineum and their ducts into the spongy urethra.
Semen
Mixture of sperm and seminal fluid (liquid that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate and Bulbourethral glands)
Volume of semen in typical ejaculation: 2.5-5 mL with 50-150 million sperm per mL.
Capacitation
The sperm is affected by secretions of the uterine tube when the sperm pass through the uterus and uterine tube.
Hemospermia
Present of blood in the semen. Most cases caused by inflammation of the blood vessels lining the seminal vesicles.
Treated with ABX.
Penis
Contains the urethra
Passageway for the ejection of semen and excretion of urine.
Cylindrical in shape.
Consists of: body, glans penis and a root.