CHAP 27 HSCI Reproductive System

Functions of the Reproductive System

Produce gametes, bring gametes together, fertilization to form a zygote, support fetal development and birth.

Primary Sex Organs (Gonads)

Produce gametes and secrete steroid sex hormones.

Accessory Reproductive Organs

Ducts, glands, and external genitalia.

Somatic Cells

Diploid (2n) cells with 46 chromosomes.

Gametes

Haploid (n) sex cells with 23 chromosomes.

Mitosis

Produces 2 genetically identical diploid cells.

Meiosis

Produces 4 genetically different haploid cells.

Function of Meiosis

Halves chromosome number and increases genetic diversity.

Meiosis I Result

Two haploid cells with 23 chromosomes each.

Meiosis II Result

Four haploid cells.

Major Structures of the Male Reproductive System

Scrotum, testes, spermatic ducts, accessory glands, penis.

Function of the Scrotum

Houses testes and regulates temperature.

Contents of the Scrotum

Testes, spermatic cord, ductus deferens, blood vessels, lymph vessels, nerves.

Structures Involved in Scrotal Temperature Regulation

Cremaster muscle, dartos muscle, pampiniform plexus.

Tunica Albuginea

Connective tissue capsule surrounding the testes.

Function of Seminiferous Tubules

Site of sperm production.

Leydig (Interstitial) Cells

Produce testosterone.

Sertoli (Sustentacular) Cells

Provide nutrients to developing sperm and secrete inhibin B.

Clinical Application: Hernia

Intestines may protrude through inguinal rings into the scrotum.

Epididymis Function

Sperm maturation and storage.

Parts of the Epididymis

Head, body, tail.

Ductus (Vas) Deferens Function

Transports sperm from epididymis to ejaculatory duct.

Ejaculatory Duct Function

Passes through prostate and empties into urethra.

Three Divisions of the Male Urethra

Prostatic, membranous, spongy (penile).

Function of the Penis

Male copulatory organ that delivers semen.

Parts of the Penis

Root, shaft, glans.

Corpus Cavernosum Function

Produces penile rigidity during erection.

Corpus Spongiosum Function

Prevents urethral collapse during erection.

Seminal Vesicles Function

Produce fructose, citric acid, coagulating enzyme; contribute 70% of semen volume.

Prostate Function

Produces nutrients for sperm, PSA, clotting enzyme.

Bulbourethral Glands Function

Lubricate and neutralize urethra.

Functions of Semen

Provides energy, enhances sperm motility, decreases cervical mucus viscosity, suppresses female immune response, antibacterial action.

Erection Mechanism

Parasympathetic stimulation causes nitric oxide release and vasocongestion.

Emission Phase

Sympathetic stimulation moves semen into urethra.

Expulsion Phase

Sympathetic stimulation expels semen.

Spermatogenesis Location

Seminiferous tubules.

When Does Spermatogenesis Begin?

Puberty.

Type A Spermatogonia

Remain as stem cells.

Type B Spermatogonia

Differentiate into sperm cells.

Spermatogenesis Sequence

Primary spermatocyte → Secondary spermatocytes → Spermatids → Sperm.

Spermiogenesis

Conversion of spermatids into mature sperm.

Parts of a Sperm Cell

Head, acrosome, midpiece, tail.

Function of the Acrosome

Contains enzymes that help penetrate the egg.

HPG Axis

Hypothalamic-pituitary-gonadal axis regulating reproduction.

GnRH Function

Stimulates release of FSH and LH.

FSH Function in Males

Stimulates sperm production.

LH Function in Males

Stimulates testosterone production.

Negative Feedback in Males

Testosterone and inhibin inhibit GnRH, FSH, and LH release.

Functions of Testosterone

Promotes spermatogenesis, accessory organ growth, anabolic effects, and secondary sex characteristics.

Effects of Testosterone Deficiency

Atrophy, decreased semen volume, impaired erection and ejaculation.

Functions of the Female Reproductive System

Oogenesis, fetal development, childbirth, infant nourishment, hormone production.

Female Gonads

Ovaries.

Internal Female Reproductive Organs

Uterine tubes, uterus, vagina.

External Female Reproductive Organs

Labia majora, labia minora, clitoris, vestibular glands.

Functions of the Ovaries

Oogenesis and sex hormone production.

Layers of the Ovary

Tunica albuginea, cortex, medulla.

Location of Ovarian Follicles

Cortex of the ovary.

Components of an Ovarian Follicle

Oocyte and surrounding follicular/granulosa cells.

Corpus Luteum

Structure formed after ovulation that secretes progesterone.

Parts of the Uterine Tube

Isthmus, ampulla, infundibulum, fimbriae.

Function of the Uterus

Nourishment and support of the developing embryo/fetus.

Regions of the Uterus

Fundus, body, cervix.

Function of Cervical Glands

Natural selection of sperm.

Layers of the Uterus

Perimetrium, myometrium, endometrium.

Functional Layer of Endometrium

Layer that grows and sheds each cycle.

Basal Layer of Endometrium

Permanent layer that regenerates the functional layer.

Functions of the Vagina

Menstrual discharge, intercourse, childbirth.

Vaginal Rugae Function

Allow stretching and recoil.

Dendritic Cells in the Vagina

Antigen-presenting immune cells.

External Female Genitalia

Mons pubis, labia majora, labia minora, vestibule, clitoris.

Clitoris

Erectile tissue involved in sexual arousal.

Parts of the Breast

Nipple, areola, suspensory ligaments, lobes, lactiferous ducts, lactiferous sinuses.

Function of Lactiferous Ducts

Transport milk to the nipple.

Oogenesis

Production of female gametes.

When Does Oogenesis Begin?

During fetal development.

Oogonia

Diploid ovarian stem cells.

Primary Oocyte

Cell formed from oogonia that begins meiosis I.

Atresia

Degeneration of ovarian follicles/oocytes.

When Does Meiosis I Pause?

Prophase I.

When Does Meiosis II Pause?

Metaphase II.

Completion of Meiosis II

Occurs only if fertilization happens.

Folliculogenesis

Maturation process of ovarian follicles.

Follicle Development Sequence

Primordial follicle → Primary follicle → Secondary follicle → Corpus luteum.

Follicular Phase

Days 1–14; follicle growth occurs.

Ovulation

Release of the secondary oocyte from the ovary.

Luteal Phase

Days 14–28; corpus luteum activity.

Dominant Follicle

Follicle selected for ovulation.

Hormone Produced by Granulosa Cells

Estrogen.

Hormonal Trigger for Ovulation

LH surge.

Path of the Released Oocyte

Abdominal cavity → Fimbriae → Uterine tube.

Mittelschmerz

Midcycle pain associated with ovulation.

Function of the Corpus Luteum

Produces progesterone after ovulation.

Hormones Secreted by Corpus Luteum

Progesterone and inhibin A.

Function of Inhibin A

Suppresses FSH and GnRH.

Three Phases of the Uterine Cycle

Menstrual, proliferative, secretory.

Menstrual Phase

Days 1–5; shedding of endometrial lining.

Proliferative Phase

Days 6–14; rebuilding of endometrium under estrogen influence.

Secretory Phase

Days 15–28; endometrial thickening under progesterone influence.

Purpose of Glycogen Accumulation in Secretory Phase

Provides nutrition for embryo.

What Happens if Fertilization Does Not Occur?

Corpus luteum degenerates, progesterone falls, menstruation occurs.