Reproductive System: Functions and Structures

Introduction to the Reproductive System

• It's not essential for an individual's survival, unlike other body systems
• Affects other systems
• Male and female reproductive organs perform two key functions:
  • Production and storage of specialized reproductive cells for creating new individuals.
  • Hormone secretion for maintaining normal sexual function.

Structures of the Reproductive System

• It ensures the continuation of the human species.
• Reproductive structures include:
  • Gonads: Organs producing gametes (reproductive cells) and hormones.
  • Ducts: Structures that receive and transport gametes.
  • Accessory Glands: Glands secreting fluids into ducts.
  • External Genitalia: Perineal structures.
• Reproductive tract consists of chambers and passageways that connect ducts to the body's exterior.
• Male and female reproductive systems have functional differences:
  • Females produce one gamete per month and retain/nurture the zygote.
  • Males produce large quantities of gametes, around half a billion sperm per day.

Male Reproductive System

• Includes the testes(male gonads)
  • Secrete androgens, such as testosterone.
  • Produce sperm.

Female Reproductive System

• Includes the ovaries (female gonads)
  • Release one immature gamete (oocyte) per month.
  • Produce hormones.
• Uterine tubes carry oocytes to the uterus. Fertilization is initiated in the tubes if sperm reaches the oocyte, where the oocyte then matures into ovum.
• The uterus encloses/supports the developing embryo.
• Vagina connects the uterus to the exterior.

Male Reproductive Structures

• Pathway of sperm includes the Testis, Epididymis, Ductus Deferens, Ejaculatory Duct, and finally the Urethra.
• Accessory glands secrete fluids into the duct system:
  • Seminal Glands
  • Prostate
  • Bulbo-urethral Glands
• Testes are approximately 5 cm long, 3 cm wide, 2.5 cm thick, and weigh 10-15 g each and hang in the scrotum.
• The scrotum, a fleshy pouch enclosing the testes, is suspended inferior to the perineum, anterior to the anus, and posterior to the base of the penis.
• Spermatic cords extend between the abdominopelvic cavity and testes and consist of fascia, muscle layers, ductus deferens, blood vessels, nerves, and lymphatic vessels.
  • Each cord begins at the entrance to the inguinal canal, a passageway through the abdominal musculature, and descends into the scrotum.
  • Blood vessels of the testes include the deferential artery, testicular artery, and pampiniform plexus of the testicular vein.
  • Nerves of testes consist of branches from the genitofemoral nerve from the lumbar plexus.
• Inguinal hernias are protrusions of visceral tissues into the inguinal canal, fairly common in males because the spermatic cord creates a weak point in the abdominal wall.
• The scrotum is divided into two chambers by the raphe, a raised thickening in scrotal surface, and each testis lies in a separate scrotal cavity.
• The tunica vaginalis is a serous membrane lining the scrotal cavity, reducing friction between opposing surfaces and composed of parietal (outer) and visceral (inner) layers.
• The Dartos muscle is a layer of smooth muscle in the dermis of the scrotum that causes characteristic wrinkling.
• Cremaster is a layer of skeletal muscle deep to the dermis that tenses the scrotum and pulls testes closer to the body.
  • Occurs with sexual arousal or decreased temperature.
• Temperature regulation in the testes is essential for normal sperm development, requiring temperatures 1.1°C lower than body temperature.
  • The muscles relax or contract to move the testes away or toward body, maintaining acceptable testicular temperatures.
• Gross anatomy of testes: The tunica albuginea is deep to tunica vaginalis, consist of dense layer of connective tissue rich in collagen fibers, is continuous with fibers surrounding epididymis, fibers form septa testis that converge near entrance to epididymis and supports blood and lymphatic vessels of testis and efferent ductules.
• Histology of testes: Septa subdivide each testis into lobules containing about 800 slender and tightly coiled seminiferous tubules.
  • Seminiferous tubules are the location of sperm production and are each about 80 cm long.
  • Added together there is nearly one-half mile in each testis.
  • Seminiferous tubules connect to the rete testis(a network of interconnected straight tubules) and efferent ductules, which then connects rete testis to epididymis.
• Connective tissue capsules surround seminiferous tubules.
• Areolar tissue fills spaces between tubules; contains blood vessels and large interstitial endocrine cells(Leydig cells).
  • Leydig cells produce androgens, dominant male sex hormones. The most important androgen is testosterone.
• The testes produce immobile sperm that are not yet capable of fertilizing an oocyte.
• Functional maturation, nourishment, storage, and transport of sperm handled by other reproductive system components.
• Immobile sperm is moved from testes into the epididymis by cilia lining efferent ductules.

Epididymis

• It Initiates the male reproductive tract.
• It is a coiled tube almost 7 m long, bound to posterior border of each testis.
• Divided into head, body, and tail.
  • The Head is the largest part and receives sperm from efferent ductules.
  • The Body lies on posterior surface of testis.
  • The Tail Begins near inferior border of testis, ascends to connection with ductus deferens, and is the primary storage location of sperm.
• Functions include monitoring and adjusting composition of produced fluid from seminiferous tubules, recycling damaged sperm, storing/protecting sperm and facilitating functional maturation.

Ductus Deferens

• Approximately 40-45 cm long and part of the spermatic cord.
• Originates at the tail of the epididymis and ascends through the inguinal canal.
• Curves inferiorly along urinary bladder, and courses toward prostate and seminal glands.
• Its lumen enlarges into the ampulla of ductus deferens, with a thick smooth muscle layer in the wall.
• Lined by pseudostratified ciliated columnar epithelium. -Peristaltic contractions propel sperm and fluid.
• Sperm can be stored here for several months in an inactive state.

Male Urethra

• Used by both urinary and reproductive systems.
• Extends 18-20 cm from urinary bladder to tip of penis.
• Divided into three regions: Prostatic, Membranous, & Spongy.

Accessory Glands

• Produce fluid component of semen, consisting of a mixture of secretions, each with distinct biochemical characteristics.
• Important glands included Seminal glands, Prostate, & Bulbo-urethral glands.
• Major functions include:
  • Activation of sperm
  • Provision of nutrients sperm need for motility
  • Propelling sperm and fluids along reproductive tract by peristaltic contractions
  • Producing buffers to counteract acidity of urethral and vaginal environments.

Seminal Glands

• Approximately 15 cm long with short side branches from body.
• Tubular glands, coiled and folded into a compact 5 cm by 2.5 cm mass.
• Extremely active secretory glands, producing majority of semen volume.

Ejaculatory Duct

• Short passageway approximately 2 cm in length.
• Formed at junction of ampulla of ductus deferens and duct of seminal gland.
• Penetrates wall of prostate.
• Empties into prostatic urethra. Prostate
• Small, muscular organ (about 4 cm in diameter) that surrounds proximal portion of urethra.
• Composed of 30–50 compound tubulo-alveolar glands encircled by smooth muscle fibers.
• Prostatic fluid is slightly acidic, forms approximately 25 percent of semen volume. Is ejected into prostatic urethra via peristalsis of prostate wall.

Prostatitis

• Prostatic inflammation can occur at any age, but most commonly afflicts older men.
• The Bulbo-urethral Glands(Cowper's Glands) are compound, tubular mucous glands about 10 mm in diameter.
  • Located at base of penis
  • Secrete thick, alkaline mucus for neutralizing urinary acids in urethra & Lubricates tip of penis.
  • The duct of each gland travels alongside spongy urethra and empties into urethral lumen.
• Semen, or Ejaculate, typically sees 2–5 mL released during ejaculation and abnormally low volume may indicate problems with prostate or seminal glands.
• For Sperm Count, semen collected after 36 hours of sexual abstinence and normal range is 20–100 million sperm/mL.
• Seminal fluid has the same osmotic concentration as blood plasma but a different composition: including high concentrations of fructose, prostaglandins which stimulate smooth muscle contractions & Fibrinogen forming temporary semen clot.
• Semen also contains enzymes including protease, seminalplasmin (antibiotic protein), prostatic enzyme, & fibrinolysin.

Penis

• Tubular organ through which distal portion of urethra passes.
• Conducts urine to exterior.
• Introduces semen into female's vagina.
• The root of penis is the fixed portion that attaches penis to body wall: attachment occurs inferior to pubic symphysis.
• The body of penis(shaft) is the tubular, movable portion.
• And the glans penis(head) is the expanded distal end that surrounds external urethral orifice.
• The dermis of the penis contains a layer of smooth muscle (continuation of dartos muscle) and overlies areolar tissue. Underneath all is the subcutaneous layer with superficial arteries, veins, and lymphatic vessels.
• Foreskin or the prepuce is fold of skin surrounding tip of penis, attaching to neck and continuing over glans penis. -Preputial glands in skin of neck and inner surface of foreskin and secrete waxy material (smegma).
• Circumcision is the Surgical removal of foreskin, can help prevent infections and penile cancer.
• Erectile tissue is located deep to areolar tissue with a dense network of elastic fibers, consisting of vascular channels separated by partitions and supported by connective/smooth muscle fibers.
  • In a resting state Arterial branches are constricted, muscular partitions are tense restricted blood flow.
  • During erection, Penis stiffens and elevates to upright position as blood flow is increases.
• Corpora Cavernosa
  • Masses of erectile tissue encircled by dense collagenous sheath separated by a thin septum, under anterior surface of flaccid penis.
  • Diverge at their bases, forming crus of penis: each crus bound to ramus of ischium and pubis via connective tissue ligaments.
  • Extend to neck of penis and surround a central artery.
• The Corpus Spongiosum is a slender erectile body that surrounds distal portion of urethra and Extends to tip of penis.
  • Surrounded by a sheath with more elastic fibers than that of corpora cavernosa.
  • Contains a pair of small arteries.

Mitosis and Meiosis and Spermatogenesis

• Mitosis:
  • Part of somatic cell division.
  • Produces two diploid (2n) daughter cells, having identical numbers and pairs of homologous chromosomes.
• Meiosis.
  • Special form of cell division involved only in production of gametes, i.e. either Sperm in males or Oocytes in females.
  • Produces four haploid (n) gametes, where Each has 23 individual chromosomes.
  • Fusion of male and female gametes produce Zygote with 46 chromosomes.
• Meiosis: Duplicated chromosomes condense Each chromosome has two chromatids in Synapsis. • Maternal and paternal chromosomes come together with matched chromatids forming tetrad Crossing over occurs here which results in exchanges of genetic material that increases genetic variation among offspring
• Includes two division cycles with two phases; Meiosis I and meiosis II.
• Meiosis I: Prophase I: Nuclear envelope disappears. Metaphase I: Tetrads line up along metaphase plate.
• Meiosis I: Anaphase I: Tetrads break up and daughter cell receives two copies of either maternal or paternal chromosome, which are then randomly distributed Telophase I ends with formation of two daughter cells with unique combinations of chromosomes. Reductional division then reduces chromosome number from diploid (2n = 46) to haploid (n = 23), both cells contain 23 chromosomes with two chromatids each
• Interphase separates meiosis I and meiosis II
• Interphase is very brief, and DNA isn't replicated Meiosis II: Consists of Prophase II and Metaphase II, and Anaphase II, in which chromatids separate then Telophase II yields four haploid cells which each then containing 23 chromosomes. Equational division has an unchanging number of chromosomes
• Spermatogenesis: sperm production that begins at puberty and lasts past seventy involving three phases:
• Cells of spermatogenesis: Spermatogonia: divide by mitosis to produce two daughter cells One remains spermatogonium, the second becomes primary spermatocyte.
• Primary spermatocytes: Begin meiosis and form secondary spermatocytes.
• Secondary spermatocytes: Differentiate into spermatids and is the final stage: Immature gametes and the last stage of spermatogenesis Sperm lose contact with tubule wall, entering fluid in lumen

Spermiogenesis in a Seminiferous Tubule

• Mitosis: spermatogonium produces two daughter cells. One remains, one goes to become primary spermatocyte and will end after 16 days.
• Meiosis I each primary spermatocyte contains 46 chromosomes lasting about 24 days and daughter cells enter meiosis 2 becoming secondary spermatocytes Meiosis II takes only a few hours ending with each containing 23 chromosomes for a total of four spermatids Spermiogenesis takes 24 days in which each spermatid matures to a sperm

Spermiogenesis

• Last step of spermatogenesis, in which Each spermatid matures into a sperm.
• At spermiation A sperm Loses attachment to nurse cell, and Enters lumen of seminiferous tubule.
• Nurse cells(Setoli cells) and they major functions include: Maintenance of blood testis barrier The support of mitosis and meiosis and spermiogenesis. Secretion of inhibin and androgen-binding protein (ABP)
• Blood testis barrier Isolates seminiferous tubules from general circulation which are maintained by nurse cells Joined by tight junctions that separate seminiferous tubule into compartments with Outer compartment, which contains spermatogonia, vs Inner compartment where meiosis and spermiogenesis occur
• Nurses stimulates mitosis and meiosis by using Follicle-stimulating hormone (FSH) which cause cells to divide/secrete Nurse cells surround and enfold spermatids and provide nutrients and chemical stimuli. As sperms leave rates of production increase , secretions also increase Nurse cells secrete androgen-binding protein (ABP) Which then: Binds androgens and this is important for elevating androgen concentration Stimulating spermiogenesis. Production of ABP is stimulated by FSH. Sperm leaving epididymisMature, but immobile To become motile (actively swimming) and fully functional: Undergo capacitation of :Sperm become motile through the process of being mixed and exposed

Seminal Glands & Fertilization

By cilia: Sperm become capable of fertilization with exposure Anatomy of sperm: Head contains membrane compartment, is essential for fertilization Middle,contains mitochondria is attached by tubules move tail by providing ATP Fertilize, the only flagellum on humans is tail. Mature sperm,Lacks cells to produce nutrients it must absorb from surrounding fluid. Hormones are needed for male reproductive Anterior releases for FSH,LH and GnRH control secretion rates of LH and Testosterone which is a steroid hormone with its own functions: Stimulates spermatogenesis, libido bone and muscle growth. Some testosterone is converted to DHT • 10 percent is testosterone this can bind same and respond and estradiol to regulate Small amounts adult of males of which 70 percent testosterone and aromatase to regulate

Female Reproductive System

• Produces gametes(oocytes) and sex hormones (estrogens and progesterone), Supports developing embryo, & Nourishes newborn infant.
• Consists of Ovaries, Uterine tubes, Uterus, Vagina, & External genitalia.
• Ovaries, tubes and uterus are attached by board ligament: These is for structural support
• Recto-uterine pouch: Pocket between posterior uterus wall and colon anterior surface
• Vesico-uterine pouch-Pocket between uterus and posterior bladder wall:

Ovaries

• Are almond shaped organs within the pelvic cavity with 3 functions: Production of immature cells Production, secrete hormones used to maintain it. ,and pituitary FSH They are also held for a mesovarium and in place by position of a ligament along side of the artery, vein with connected.
• Histlogical structure can be used for identification purposes: Visceral peritoneum-germinal surface consist of the inner and outer layers Stroma inner ovary produce gametes with cortex outer surface and medullar innter Uterine functions: Or fallopian tubes is the most important for the hollow transport of mucus. the Oocytes by which are approximately 13cm (5 inches) it. The three part are:
• Infundibulum is the funnel open towards the tube Fimbriae( the projections within, which are the cilia, this causes infections in the tube
• Ampiulia is the middle segment that
• Ismthus which is a short segment between uterine cavity Transports
• Fertilization takes about 24 to 12 hours for it to take place Pre embryonic cells that allow capacitaito and produce nutrients after sperm has made impact in isthmus

Uterus

• Provides support, protection, removes waste during weeks and is made possible thought ligaments:
• Uterosacral: posterior
• Antero: roundligament
• Body or fundus
• cervix portion near vagina
• External OS is the opening surrounded by cervix
• Cervcial OS passage to what can be call of vascular region
• Branch of:
• Arteries uterine: a branch on iliac Ovarian arteries branch of aorta

Uterine Functions

• Peritmetrium is a layer and covers the lining.
• Myometrium of which is the layer with smooth muscler arrangement
• Endometrium is inner and supports to growing to the fetus also with glad tissue It contributions to 10 percent of vessels and supports as the fetus is there.
• The uterine undergoes a functional change every month The epithelial cells multiply and restore integrity
• As it restore layers is restored function by Epithelial cells : in smooth fashion produce with ciliary and a mucosal surface
• The wall consists of straight,radial and spriral Vagina-Tube passage way to both uterus,sperm elimination that are about 9 inches is
• Vaginal fornix project into which has recesseal walls
• These consists of:
• Bulbospongiosus: a fold that has smooth muscles with vessels Hymen elastic like fold Vaginal wall - non keratinizaition Vaginal prolapse with elastic lamina

Female Genatalia and Breasts

• Discharge in urethra and opening small projection of what similar in development Glands the form the clitori • Erection can happens due to what is connected vessel known has the caposum cordis of it • Vestibular and secrete on the surface (lesser glands secrete near opening( greater gland ) • Mons pubis where margins form vulva protect/ store adipose covered by hair and glands .

Mammary Gland and Nipple

• The specialized section of skin that system that produces lactation • Is controlled by adipose tissues • These functions with the glands that contain lobe like tubes that are dense connected. • 15 an 20 ducts connect and from the sinus Suspendory, and Connect where separate muscle are. • After the breast it is composed of tublues with tubes of multiply alveol The Secretion happen the pregnancy by which the glands occur and is a active state with more activity with hormones Oogenosis: production and begin before accelerates and stops.

• Oogonia which are the female stem cells undergoes from mitosis to produce diploid.

Oogenesis

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• Menopause happens about about 45-55.
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