💀Anatomy and Physiology I Unit 27 – The Reproductive System

Key Structures and Functions

• Reproductive system consists of gonads (testes in males, ovaries in females) that produce gametes (sperm and eggs) and secrete hormones
• Accessory structures include ducts, glands, and external genitalia that transport and facilitate the union of gametes
• Testes are located in the scrotum, a skin-covered sac that maintains a lower temperature for optimal sperm production
  • Seminiferous tubules within the testes are the site of sperm production and maturation
• Ovaries are located in the pelvic cavity and contain follicles that house developing oocytes
  • Ovulation occurs when a mature follicle releases an oocyte into the fallopian tube
• Uterus is a muscular organ that supports the development of the fetus during pregnancy
  • Endometrium is the inner lining of the uterus that thickens in preparation for implantation
• Vagina is an elastic, muscular canal that serves as the birth canal and receives the penis during sexual intercourse
• Mammary glands in the breasts produce milk to nourish the newborn infant

Hormones and Regulation

• Hypothalamus releases gonadotropin-releasing hormone (GnRH), stimulating the anterior pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
• FSH stimulates the development of ovarian follicles in females and supports spermatogenesis in males
• LH triggers ovulation and the formation of the corpus luteum in females, and stimulates testosterone production in males
• Testosterone is the primary male sex hormone produced by the Leydig cells in the testes
  • Testosterone is responsible for the development of male secondary sexual characteristics and supports spermatogenesis
• Estrogen and progesterone are the primary female sex hormones produced by the ovaries
  • Estrogen promotes the development of female secondary sexual characteristics and prepares the uterus for implantation
  • Progesterone maintains the uterine lining during pregnancy and suppresses further ovulation
• Negative feedback loops regulate hormone levels to maintain homeostasis in the reproductive system

Male Reproductive System

• Testes are the primary male reproductive organs, responsible for sperm production and testosterone secretion
• Epididymis is a coiled tube attached to each testis, where sperm mature and are stored
• Vas deferens is a muscular tube that transports sperm from the epididymis to the ejaculatory ducts
• Seminal vesicles, prostate gland, and bulbourethral glands contribute to semen production
  • Seminal vesicles secrete a fluid rich in fructose, which provides energy for sperm
  • Prostate gland secretes an alkaline fluid that neutralizes the acidic environment of the vagina
  • Bulbourethral glands secrete a clear mucus that lubricates the urethra during ejaculation
• Penis is the male copulatory organ, composed of erectile tissue that becomes engorged with blood during sexual arousal
• Urethra is a tube that runs through the penis, serving as a passage for both urine and semen

Female Reproductive System

• Ovaries are the primary female reproductive organs, responsible for oocyte production and hormone secretion
• Fallopian tubes are paired tubes that transport oocytes from the ovaries to the uterus
  • Fertilization typically occurs in the ampulla, the widest part of the fallopian tube
• Uterus is a hollow, muscular organ that supports the development of the fetus during pregnancy
  • Myometrium is the muscular layer of the uterus that contracts during labor and delivery
• Cervix is the lower, narrow portion of the uterus that connects to the vagina
  • Cervical mucus changes consistency throughout the menstrual cycle, becoming more permeable to sperm during ovulation
• Vagina is a muscular canal that extends from the cervix to the external genitalia
  • Vaginal pH is typically acidic, providing a protective barrier against pathogens
• Vulva refers to the external female genitalia, including the labia, clitoris, and vaginal opening

Gametogenesis and Fertilization

• Gametogenesis is the process of producing haploid gametes from diploid cells through meiosis
• Spermatogenesis occurs in the seminiferous tubules of the testes and involves the differentiation of spermatogonia into mature spermatozoa
  • Spermiogenesis is the final stage of spermatogenesis, where spermatids undergo structural changes to become motile sperm
• Oogenesis occurs in the ovaries and involves the development of primary oocytes into mature ova
  • Oogenesis begins during fetal development but is arrested until puberty, with only one oocyte typically maturing per menstrual cycle
• Fertilization is the fusion of a sperm cell with an oocyte, forming a zygote
  • Acrosome reaction is the release of enzymes from the sperm head that facilitate penetration of the oocyte's protective layers
• Cleavage is the rapid series of mitotic divisions that occur after fertilization, resulting in the formation of a blastocyst
• Implantation is the attachment of the blastocyst to the uterine wall, marking the beginning of pregnancy

Pregnancy and Fetal Development

• Pregnancy is divided into three trimesters, each lasting approximately three months
• First trimester is characterized by rapid cell differentiation and the formation of major organ systems
  • Embryonic stage lasts from fertilization until the end of the eighth week, during which the embryo develops from a blastocyst to a recognizable human form
• Second trimester is a period of continued growth and development, with the fetus becoming more active and responsive to stimuli
  • Quickening refers to the first detectable fetal movements, typically felt by the mother around 16-20 weeks
• Third trimester is marked by rapid fetal growth and the maturation of organ systems in preparation for birth
  • Lightening is the descent of the fetus into the pelvic cavity, occurring a few weeks before labor begins
• Labor is the process of giving birth, involving regular uterine contractions that dilate the cervix and expel the fetus and placenta
• Lactation is the production of milk by the mammary glands, triggered by the hormone prolactin following delivery

Common Disorders and Diseases

• Infertility is the inability to conceive after 12 months of regular, unprotected sexual intercourse
  • Causes may include hormonal imbalances, structural abnormalities, or genetic factors
• Polycystic ovary syndrome (PCOS) is a hormonal disorder characterized by irregular menstrual cycles, excess androgen production, and the presence of multiple cysts on the ovaries
• Endometriosis is a condition in which endometrial tissue grows outside the uterus, causing pelvic pain and potential fertility issues
• Erectile dysfunction is the inability to achieve or maintain an erection sufficient for sexual intercourse
  • Causes may include cardiovascular disease, diabetes, or psychological factors
• Sexually transmitted infections (STIs) are diseases transmitted through sexual contact, such as chlamydia, gonorrhea, and HIV
  • Prevention methods include using condoms and regular STI testing
• Testicular and ovarian cancers are malignancies that develop in the gonads, often presenting with symptoms such as lumps, pain, or abnormal bleeding

Clinical Applications and Relevance

• Contraception methods are used to prevent pregnancy, including hormonal birth control (pills, patches, injections), intrauterine devices (IUDs), and barrier methods (condoms, diaphragms)
  • Emergency contraception (Plan B) can be used to prevent pregnancy after unprotected sex or contraceptive failure
• Assisted reproductive technologies (ART) are medical procedures used to treat infertility, such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI)
  • IVF involves fertilizing an oocyte with sperm in a laboratory dish and transferring the resulting embryo to the uterus
• Prenatal care is the medical care provided to a pregnant woman to monitor the health of both the mother and the developing fetus
  • Ultrasound imaging is used to assess fetal growth, detect abnormalities, and determine gestational age
• Menopause is the permanent cessation of menstrual cycles, typically occurring between the ages of 45 and 55
  • Hormone replacement therapy (HRT) may be used to alleviate menopausal symptoms such as hot flashes and vaginal dryness
• Prostate-specific antigen (PSA) testing is a blood test used to screen for prostate cancer in men
  • Digital rectal exam (DRE) is another screening method used to detect abnormalities in the prostate gland
• HPV vaccination is recommended for both males and females to prevent infection with human papillomavirus, which can cause cervical, anal, and oropharyngeal cancers