General Biology II - Second Semester Notes for Exam Prep

MALE REPRODUCTIVE SYSTEM

  • Developmental Origin

    • Male and female reproductive systems develop from similar embryonic tissues.
    • Early embryonic development shows male and female embryos are indistinguishable.
    • Adult male and female reproductive systems share functional similarities.

  • Main Functions

    • Produces hormones (e.g. testosterone).
    • Produces sperm cells.
    • Delivers sperm to the female reproductive system.

ORGANS

I. TESTES
  • Two testes produce millions of sperm cells and hormones.
  • Hormones influence male pubertal development.
  • Size: Ovoid structures measuring about 5 cm long and 3 cm wide.
  • Located in the scrotal sac (scrotum) for temperature regulation.
  • Descend during the 7th or 8th month of fetal development.
Medical or Clinical Relevance
  • Cryptorchidism: Failure of testes to descend; common pediatric issue, often treated with surgery (Orchiopexy).
  • Inguinal Hernia: Weak spots in the abdominal wall after descent that can become enlarged or rupture, potentially compressing intestines; surgery is often required.
B. SPERMATOGENESIS
  • Sperm development from spermatogonium (sperm stem cells) formed during fetal development.
  • Dormancy until puberty; maturation occurs in seminiferous tubules, resulting in spermatozoa.
C. SEMINIFEROUS TUBULES
  • Site of sperm production within each testis.
II. SCROTUM
  • Bag of skin containing the testes; hangs outside abdominopelvic cavity to maintain lower temperatures.
  • Contains paired testes with a midline septum.
A. SCROTAL WALL
  • Dartos Muscle: Smooth muscle causing skin wrinkling.
  • Cremaster Muscle: Controls the position of the testes based on temperature.
B. INSIDE THE SCROTUM
  • Tunica Vaginalis: Encloses each testis, derivative of the peritoneum.
  • Tunica Albuginea: Fibrous capsule covering each testis; forms septa dividing the testis into lobules with seminiferous tubules.
III. SPERM DUCT
  • Transports sperm from testes; includes vas deferens, nerves, and blood vessels.
IV. PENIS
  • Functions in urination and sexual intercourse; composed of erectile tissues and blood vessels.
  • Corpora Cavernosum: Large erectile tissue spaces; Corpus Spongiosum surrounds the urethra.
  • Glans Penis: Enlarged tip of the penis with sensory receptors; covered by foreskin (prepuce).
A. INTERNAL STRUCTURE
  • Contains three sections of urethra: Prostatic, Membranous, and Spongy Urethra.
V. URETHRA
  • Dual passage for urine and reproductive fluids.
VI. EPIDIDYMIS
  • Storage and maturation area for sperm.
  • Contracts upon ejaculation to expel sperm into the ductus deferens.
A. EPIDIDYMAL CYST
  • Common benign cysts that can occur in the epididymis.
VII. ACCESSORY GLANDS
  • Seminal Vesicles: Secretes 60% of semen volume, contains fructose for sperm energy.
  • Prostate Gland: Activates sperm; provides citrate and proteolytic enzymes; encircles urethra.
  • Bulbourethral Glands: Secretes alkaline mucus to neutralize acidity in the urethra prior to ejaculation.
VIII. FORESKIN OR PREPUCE
  • Retractable fold covering the penis tip; circumcision may be performed.
IX. BLADDER
  • Temporary storage for urine, signaling to eliminate waste.

SPERM STRUCTURE

  • Head: Contains DNA, acrosome (enzymes for penetrating egg).
  • Midpiece: Contains spiraled mitochondria for energy.
  • Tail: Flagellum for motility.

PATHWAY OF SPERM

  • Pathway: Seminiferous tubules → Epididymis → Vas Deferens → Seminal vesicle → Prostate gland → Prostatic urethra (through Bulbourethral gland) → Membranous urethra → Penile urethra.

FEMALE REPRODUCTIVE SYSTEM

ROLES

  • Produces eggs in ovaries; fertilized eggs develop into embryos in the uterus.
  • Provides environment for growth and nourishment of fetus; regulated by hormonal actions.

ORGANS

I. OVARY
  • Small, solid organs that produce eggs and hormones (estrogen and progesterone).
  • Approximately 2 cm in length, suspended by ligaments in the pelvic cavity.
II. OVIDUCT (FALLOPIAN TUBE)
  • Connects ovary to uterus; ciliated lining aids in egg transport.
  • Site of fertilization.
A. TUBAL LIGATION
  • Surgical procedure for female sterilization by blocking oviducts.
B. FOUR PARTS OF OVIDUCT
  • Fimbriae: Capture ovulated egg.
  • Infundibulum: Funnel-shaped region near ovary.
  • Ampulla: Site of fertilization; widest part.
  • Isthmus: Narrow connected section to uterine cavity.
III. UTERUS
  • Thick-walled muscular organ located in the pelvis; functions to nourish the fetus.
A. PARTS OF UTERUS
  • Fundus: Rounded upper region.
  • Body: Main section; common site for implantation.
  • Cervix: Lower part connecting to vagina.
IV. UTERINE WALL
  • Perimetrium: Outer membrane, part of peritoneum.
  • Myometrium: Thick smooth muscle layer; expands during pregnancy.
  • Endometrium: Mucous membrane; responds to hormonal cycles, shed during menstruation.
V. CERVIX
  • Maintains uterine containment during pregnancy; opens during labor.
A. CERVICAL CANAL
  • Communicates with vagina via the external os and uterine body via the internal os.
VI. VAGINA
  • Muscular canal for sexual intercourse and childbirth; enables menstrual fluid exit.
VII. FEMALE EXTERNAL GENITALIA (VULVA)
  • Collective term for external structures in the pubic area.
A. PARTS OF VULVA
  • Mons Pubis: Fatty pad over the pubic symphysis.
  • Labia Majora and Minora: Skin folds around urethral and vaginal openings.
  • Clitoris: Erectile tissue structure.
VIII. BARTHOLIN’S GLANDS
  • Provide vaginal lubrication; potential for cyst formation.
IX. MAMMARY GLANDS (BREASTS)
  • Produce milk; structures enhance lactation.

OOGENESIS

  • Formation of female gametes begins in fetal life; produces primary oocytes.

MENSTRUAL CYCLE

  • Average duration: 28 days; divided into four phases.

FOUR PHASES

I. MENSTRUAL PHASE (DAY 1 TO 5)
  • Shedding of endometrium; blood loss varies.
II. FOLLICULAR PHASE (DAY 1 TO 13)
  • Uterus lining thickens; FSH stimulates egg maturation.
III. OVULATION PHASE (DAY 14)
  • LH triggers release of the matured egg; typically on day 14.
IV. LUTEAL PHASE (DAY 15 TO 28)
  • Corpus luteum releases hormones; preps for potential embryo implantation.

ASEXUAL AND SEXUAL REPRODUCTION

ASEXUAL REPRODUCTION

  • Single-organism reproduction, offspring genetically identical.
  • Includes binary fission, budding, vegetative propagation, regeneration, fragmentation, sporulation.

SEXUAL REPRODUCTION

  • Combination of male and female gametes, variability in offspring.
  • Can occur internally (mammals, birds) or externally (fish, amphibians).

FEEDBACK MECHANISM AND HOMEOSTASIS

  • Maintaining physiological balance; involves sensors, control centers, and targets.

TYPES OF FEEDBACK

I. POSITIVE FEEDBACK
  • Amplifies response to stimuli.
II. NEGATIVE FEEDBACK
  • Counteracts change; maintains internal balance.

THERMOREGULATION

  • Homeotherms: Can regulate body temperature.
  • Poikilotherms: Depend on environmental heat source.

GLUCOSE LEVEL REGULATION

  • Insulin and Glucagon: Control blood sugar levels through hepatic action.

WATER REGULATION

  • Involves kidneys; maintains hydration and electrolyte balance.