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The Reproductive System: A Comprehensive Overview, Study notes of Anatomy

A detailed overview of the human reproductive system, covering both male and female anatomy and physiology. It delves into the processes of spermatogenesis and oogenesis, hormonal regulation, and the stages of pregnancy and labor. Well-organized and includes clear diagrams and explanations, making it a valuable resource for students of biology and related fields.

Typology: Study notes

2024/2025

Available from 01/11/2025

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C.A.B.M. | 2024
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The Reproductive System
Overview of the Reproductive System
Primary Sex Organs (Gonads):
o Male: Testes
o Female: Ovaries
o Functions:
Produce gametes (sperm and
ova).
Secrete sex hormones.
Male Reproductive System Anatomy
Testes:
o Contained within the scrotum.
o Connected to the trunk via
spermatic cord, housing:
Houses blood vessels, nerves,
and the ductus deferens.
Coverings of the testes:
o Tunica Albuginea:
Dense connective tissue
capsule around each testis.
o Septis
Extensions of the capsule that
extend into the testis and
divide it into lobules
Lobules:
Contain seminiferous
tubules (sperm
production sites).
Tightly coiled
structures
Function as sperm-
forming factories
Empty sperm into the
rete testis
Rete Testis:
Collect sperm for
transport to the
epididymis.
Sperm travels from the rete
testis to the epididymis
Interstitial Cells:
Produce testosterone.
Duct System:
o Includes the epididymis, ductus
(vas) deferens, and urethra, which
transport sperm from the body.
o Epididymis:
6 meters long, serves as a
storage and maturation site
for sperm.
Found along the posterior
lateral side of the testis
First part of the male duct
system
Temporary storage site for
immature sperm
o Ductus (Vas) Deferens:
Runs from the epididymis via
the spermatic cord through
the inguinal canal and arches
over the urinary bladder
Ampullaend of the
ductus deferens,
which empties into
the ejaculatory duct
Ejaculatory duct
passes through the
prostate to merge with
the urethra
Ejaculationsmooth
muscle in the walls of
the ductus deferens
create peristaltic
waves to squeeze
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The Reproductive System

Overview of the Reproductive System

  • Primary Sex Organs (Gonads): o Male: Testes o Female: Ovaries o Functions: ▪ Produce gametes (sperm and ova). ▪ Secrete sex hormones. Male Reproductive System Anatomy
  • Testes : o Contained within the scrotum. o Connected to the trunk via spermatic cord, housing : ▪ Houses blood vessels, nerves, and the ductus deferens.
  • Coverings of the testes : o Tunica Albuginea : ▪ Dense connective tissue capsule around each testis. o Septis ▪ Extensions of the capsule that extend into the testis and divide it into lobules ▪ Lobules : ▪ Contain seminiferous tubules (sperm production sites). ▪ Tightly coiled structures ▪ Function as sperm- forming factories ▪ Empty sperm into the rete testis ▪ Rete Testis : ▪ Collect sperm for transport to the epididymis. ▪ Sperm travels from the rete testis to the epididymis ▪ Interstitial Cells : ▪ Produce testosterone.
  • Duct System : o Includes the epididymis , ductus (vas) deferens , and urethra, which transport sperm from the body. o Epididymis : ▪ 6 meters long, serves as a storage and maturation site for sperm. ▪ Found along the posterior lateral side of the testis ▪ First part of the male duct system ▪ Temporary storage site for immature sperm o Ductus (Vas) Deferens : ▪ Runs from the epididymis via the spermatic cord through the inguinal canal and arches over the urinary bladder ▪ Ampulla —end of the ductus deferens, which empties into the ejaculatory duct ▪ Ejaculatory duct — passes through the prostate to merge with the urethra ▪ Ejaculation —smooth muscle in the walls of the ductus deferens create peristaltic waves to squeeze

sperm forward  Vasectomy —cutting of the ductus deferens at the level of the testes prevents transportation of sperm (form of birth control) ▪ Transports sperm via peristalsis. o Urethra : ▪ Extends from the base of the urinary bladder to the tip of the penis ▪ Carries both urine and sperm ▪ Sperm enters from the ejaculatory duct ▪ Three parts: ▪ Prostatic urethra— surrounded by prostate gland. ▪ Membranous urethra—prostatic urethra to penis ▪ Spongy (penile) urethra—runs the length of the penis to the external urethral orifice. o Ejaculation causes the internal urethra sphincter to close ▪ Prevents urine from passing into the urethra ▪ Prevents sperm from entering the urinary bladder.

  • Accessory Organs : o Seminal Vesicles : Located at the base of the bladder; produce a thick, yellowish secretion (60% of semen) that contains: ▪ Fructose (sugar), vitamin C, prostaglandins, other substances that nourish and activate sperm o Duct of each seminal vesicle joins that of the ductus deferens on each side to form the ejaculatory duct o Prostate Gland : Activates sperm with its secretions. ▪ Encircles the upper (prostatic) part of the urethra ▪ Secretes a milky fluid ▪ Fluid enters the urethra through several small ducts o Bulbourethral Glands : Pea-sized glands inferior to the prostate ▪ Produce a thick, clear mucus ▪ Mucus cleanses the spongy (penile) urethra of acidic urine prior to ejaculation ▪ Mucus serves as a lubricant during sexual intercourse. o Semen ▪ Milky white mixture of sperm and accessory gland secretions ▪ Components of accessory gland secretions
  • Meiosis o Special type of nuclear division that differs from mitosis o Occurs in the gonads o Includes two successive divisions of the nucleus (meiosis I and II) o Results in four daughter cells (gametes)
  • Spermiogenesis : o Maturation of spermatids into motile sperm cells. o Spermatids are nonmotile and not functional as sperm o A streamlining process is needed to strip excess cytoplasm from a spermatid and modify it into a sperm o A sperm has three regions: head, midpiece, tail o Acrosome sits anterior to the sperm head (nucleus) o The entire process of spermatogenesis, including spermiogenesis, takes 64 to 72 days Testosterone Production - Hypothalamus releases gonadotropin- releasing hormone (GnRH), stimulating the anterior pituitary to release: o FSH : Stimulates sperm production. o LH : Stimulates testosterone production. - Testosterone o Most important hormonal product of the testes o Stimulates reproductive organ development o Underlies sex drive o Causes secondary sex characteristics ▪ Deepening of voice ▪ Increased hair growth ▪ Enlargement of skeletal muscles ▪ Increased bone growth and density

Female Reproductive System Anatomy

  1. Ovaries : o Produce ova and hormones (estrogen, progesterone). o Ovarian Follicles : ▪ Contain oocytes (immature egg) and follicular cells; primary follicle o Ovulation : ▪ Release of a secondary oocyte; the follicle ruptures when the egg is mature and ready to be ejected from the ovary; occurs about every 28 days ▪ The ruptured follicle is transformed into a corpus luteum o Corpus Luteum : ▪ Produces progesterone post- ovulation. o Ovary support ▪ Suspensory ligaments secure the ovaries to the lateral walls of the pelvis ▪ Ovarian ligaments anchor ovaries to the uterus medially ▪ Broad ligaments, a fold of peritoneum, enclose and hold the ovaries in place
  2. Duct System : o Uterine (Fallopian) Tubes : Transport oocytes; site of fertilization. ▪ Form the initial part of the duct system ▪ Receive the ovulated oocyte from the ovaries ▪ Empty into the uterus ▪ Little or no contact between ovaries and uterine tubes ▪ Supported and enclosed by the broad ligament o Structure: ▪ Infundibulum ➢ Distal, funnel-shaped end ▪ Fimbriae ➢ Fingerlike projections of the infundibulum ➢ Receive the oocyte from the ovary ➢ Cilia located inside the uterine tube transport the oocyte o Uterus : ▪ Layers: endometrium, myometrium, perimetrium.

o Swollen with blood during sexual excitement

  • The clitoris lacks a reproductive duct f) Perineum
  • Diamond-shaped region between the anterior ends of the labial folds, anus posteriorly, and ischial tuberosities laterally Oogenesis and the Menstrual Cycle
  • The total supply of eggs is determined by the time a female is born
  • Ability to release eggs begins at puberty with the onset of the menstrual cycle
  • Reproductive ability ends at menopause (in female’s fifties)
    1. Oogenesis : o Process of producing ova (eggs) o Starts before birth with primary oocytes arrested in prophase I. o Oogonia are female stem cells found in a developing fetus o Oogonia undergo mitosis to produce primary oocytes that are surrounded by cells that form primary follicles in the ovary o Resumes at puberty; secondary oocyte is ovulated monthly (by FSH ). o Meiosis II completes only if fertilization occurs. o Cyclic monthly changes constitute the ovarian cycle o Meiosis starts inside maturing follicle ▪ First meiotic division produces a larger secondary oocyte and a smaller first polar body ▪ A vesicular follicle contains a secondary oocyte (maturation from a primary follicle takes about 14 days) o Ovulation of a secondary oocyte occurs with the release of luteinizing hormone (LH) o Secondary oocyte is released and surrounded by a corona radiata - Meiosis is completed after ovulation only if sperm penetrates the oocyte o Ovum is produced o Two additional polar bodies are produced - Once ovum is formed, the 23 chromosomes can be combined with the 23 chromosomes of the sperm to form the fertilized egg (zygote) - If the secondary oocyte is not penetrated by a sperm, it dies and does not complete meiosis to form an ovum - Meiosis o Males—produces four functional sperm o Females—produces one functional ovum and three tiny polar bodies - Sex cell size and structure o Sperm are tiny, motile, and equipped with nutrients in seminal fluid o Egg is large, is nonmotile, and has nutrient reserves to nourish the embryo until implantation 2. Uterine Cycle : o Menstrual Phase (Days 1–5): Shedding of the functional endometrium. o Proliferative Phase (Days 6–14): Endometrium rebuilds; ovulation occurs.

o Secretory Phase (Days 15–28): Prepares for implantation. Hormonal Regulation in Females

  • Controlled by FSH and LH: o FSH stimulates follicle growth. o LH triggers ovulation and corpus luteum formation.
  • Estrogens are produced by follicle cells o Cause secondary sex characteristics ▪ Enlargement of accessory organs of the female reproductive system ▪ Development of breasts ▪ Appearance of axillary and pubic hair ▪ Increase in fat beneath the skin, particularly in hips and breasts ▪ Widening and lightening of the pelvis ▪ Onset of menses (menstrual cycle)
  • Progesterone is produced by the corpus luteum o Production continues until LH diminishes in the blood o Does not contribute to the appearance of secondary sex characteristics o Other major effects ▪ Helps maintain pregnancy ▪ Prepares the breasts for milk production Uterine (Menstrual) Cycle
  • Cyclic changes of the endometrium, about 28 days in length
  • Regulated by cyclic production of estrogens and progesterone by the ovaries
  • FSH and LH, from the anterior pituitary, regulate the production of estrogens and progesterone by the ovaries
  • Ovulation typically occurs about midway through cycle, on day 14 Stages of the menstrual cycle
  • Menstrual phase (Days 1–5): o Functional layer of the endometrium is sloughed o Bleeding occurs for 3 to 5 days o Ovarian hormones are at their lowest levels o By day 5, growing ovarian follicles are producing more estrogen
  • Proliferative stage (Days 6– 14 ): o Regeneration of functional layer of the endometrium ▪ Endometrium is repaired, thickens, and becomes well vascularized o Estrogen levels rise o Ovulation occurs in the ovary at the end of this stage
  • Secretory stage (Days 15–28): o Levels of progesterone rise and increase the blood supply to the endometrium, which becomes more vascular o Endometrium increases in size and readies for implantation
  • If fertilization does occur: o Embryo produces a hormone that causes the corpus luteum to continue producing its hormones
  • If fertilization does NOT occur: o Corpus luteum degenerates as LH blood levels decline o The phases are repeated about every 28 days

Events of Embryonic & Fetal Development

  1. Stages of Development : o ZygoteMorulaBlastocystEmbryoFetus. o Implantation occurs around day 7 post-ovulation.
  • Zygote o First cell of a new individual o The zygote is the result of the fusion of DNA from sperm and egg o The zygote begins rapid mitotic cell divisions, known as cleavage, 24 hours after fertilization o The zygote journeys down the uterine tube, moving toward the uterus
  • Cleavage o Rapid series of mitotic divisions that begins with the zygote o 3 days after ovulation, the embryo reaches the uterus and floats as a morula, a ball of 16 cells
  • Blastocyst (chorionic vesicle) o Hollow, ball-like structure of 100 cells or more o Secretes human chorionic gonadotropin (hCG) to induce the corpus luteum to continue producing hormones, preventing menses, until the placenta assumes its role
  • Functional areas of the blastocyst
  1. Trophoblast —large fluid-filled sphere
  2. Inner cell mass —cluster of cells to one side
  • By day 7 after ovulation, the blastocyst has attached to the endometrium
  • Inner cell mass of blastocyst develops into: o Primary germ layers
  1. Ectoderm —outside layer, which gives rise to nervous system and epidermis of skin
  2. Endoderm —inside layer, which forms mucosae and associated glands
  3. Mesoderm —middle layer, which gives rise to everything else
  4. Placenta : o Provides oxygen and nutrients while removing waste. o Functions as an endocrine organ producing hCG, estrogen, and progesterone.
  • After implantation, the trophoblast of the blastocyst develops chorionic villi (projections) o Chorionic villi combine with tissues of the uterus to form the placenta
  • Once the placenta has formed, the amnion is attached to the placenta by an umbilical cord o Amnion is a fluid-filled sac that surrounds the embryo o Umbilical cord is a blood vessel– containing stalk of tissue
  • Placenta o Forms a barrier between mother and embryo (blood is not exchanged) o Delivers nutrients and oxygen o Removes wastes from embryonic blood o Becomes an endocrine organ and takes over for the corpus luteum (by end of second month); produces

estrogen, progesterone, and other hormones that maintain pregnancy

  1. Fetal Growth : o Organ systems are established by week 8. o Growth and maturation continue until birth.
  • All organ systems are formed by the end of the eighth week
  • Activities of the fetus are growth and organ specialization
  • The fetal stage is one of tremendous growth and change in appearance Effects of Pregnancy on the Mother
  • Pregnancy —period from conception until birth
  • Anatomical changes o Enlargement of the uterus o Accentuated lumbar curvature (lordosis) o Relaxation of the pelvic ligaments and pubic symphysis due to production of the hormone relaxin Physiological changes
  • Gastrointestinal system o Morning sickness is common and is due to elevated progesterone and estrogens o Heartburn is common because of organ crowding by the fetus o Constipation is caused by declining motility of the digestive tract
  • Urinary system o Kidneys have additional burden and produce more urine o The uterus compresses the bladder, causing stress incontinence

Expulsion

  • Infant passes through the cervix and vagina
  • Can last as long as 2 hours, but typically is 50 minutes in the first birth and 20 minutes in subsequent births
  • Normal delivery is head-first (vertex position)
  • Breech presentation is buttocks-first Placental stage
  • Delivery of the placenta
  • Usually accomplished within 15 minutes after birth of infant
  • Afterbirth—placenta and attached fetal membranes
  • All placental fragments should be removed to avoid postpartum bleeding
  1. Hormonal Mechanisms : o Positive feedback of oxytocin and prostaglandins facilitates contractions. Developmental and Lifecycle Changes
  • Puberty : o Initiates reproductive capability; marked by secondary sexual characteristics.
  • Menopause : o End of female reproductive capability; cessation of menstruation. Contraception
  1. Hormonal Methods : Pills, patches, implants.
  2. Barrier Methods : Condoms, diaphragms.
  3. Sterilization : Vasectomy, tubal ligation.
  4. Emergency Contraceptives : Morning-after pill. Detailed: Developmental Aspects of the Reproductive System
  • Males o Enlargement of testes and scrotum signals onset of puberty (often around age 13)
  • Females o Budding breasts signal puberty (often around age 11) o Menarche —first menstrual period (usually occurs about 2 years later)
  • Menopause —a whole year has passed without menstruation o Ovaries stop functioning as endocrine organs o Childbearing ability ends o Hot flashes and mood changes may occur
  • There is a no equivalent of menopause in males, but there is a steady decline in testosterone A Closer Look: Contraception
  • Contraception —birth control
  • Birth control pill —most-used contraceptive

o Relatively constant supply of ovarian hormones from pill is similar to pregnancy o Ovarian follicles do not mature, ovulation ceases, menstrual flow is reduced

  • Morning-after pill (MAP) o Taken within 3 days of unprotected intercourse
    o Disrupts normal hormonal signals to the point that fertilization is prevented
  • Other hormonal birth control devices cause cervical mucus to thicken o Minipill (tablet) o Norplant (rods placed under the skin)
  • Intrauterine device (IUD) o Plastic or metal device inserted into uterus o Prevents implantation of fertilized egg
  • Sterilization o Tubal ligation (females)—cut or cauterize uterine tubes o Vasectomy (males)—cut or cauterize the ductus deferens - Coitus interruptus —withdrawal of penis prior to ejaculation - Rhythm (fertility awareness)—avoid intercourse during period of ovulation or fertility o Record daily basal temperature (body temperature rises after ovulation) o Record changes in pattern of cervical mucus - Barrier methods o Diaphragms o Cervical caps o Condoms o Spermicidal foams o Gels o Sponges - Abortion —termination of pregnancy - Miscarriage —spontaneous abortion is common and frequently occurs before a woman knows she is pregnant - RU486 , or ― abortion pill‖— induces miscarriage during first 7 weeks of pregnancy Reference: Marieb, E. N., & Keller, S. (2018). Essentials of human anatomy & physiology (12th ed., pp. 564 – 596 ). Pearson Education, Inc.