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Chapter 31

The Reproductive System

The gonadotrophin-releasing hormone, GnRH, and the gonadotrophins regulate endometrial changes during the menstrual cycle. Starting at puberty, GnRH …
The paired testes are the male gonads. Each testis, weighing 10 to 15 grams, measures about 5 cm long, 3 cm wide, and 2.5 cm thick. The tunica albuginea, …
The tunica albuginea of each testis extends inward to form fibrous partitions, or septa testis, dividing it into internal compartments called lobules. …
Spermatogenesis begins at puberty and continues late into life, producing sperm in the seminiferous tubules. It has three main stages — mitosis, …
The epididymis, vas deferens, ejaculatory duct, and urethra form the accessory ducts responsible for sperm maturation and transportation. The epididymis …
The penis, part of the external male genitalia, is involved in both sexual reproduction and urination. Its cylindrical shape has three primary regions …
Inside the seminiferous tubule of the testis, fluid from the Sertoli cells pushes the non-motile sperm through a series of straight tubules into the rete …
The paired seminal and bulbourethral glands and the single prostate gland comprise the accessory male reproductive glands. The 5-centimeter-long seminal …
Males release 2-5 ml of semen, a mixture of mature sperm and accessory gland fluids. The 60 μm long mature sperm cells consist of the head, neck, …
In response to the sexual stimuli, the parasympathetic neurons stimulate the local release of nitric oxide, or NO, dilating the arterioles in the penis. …
Gonadotropin-releasing hormone from the hypothalamus stimulates the pituitary gland to release follicle-stimulating hormone, FSH and luteinizing hormone, …
The external female genitalia are structures located outside the vagina. They include the mons pubis, labia, clitoris, and vestibule structures and are …
The vagina is a fibromuscular tube, about 3 to 4 inches long, located between the urinary bladder and the rectum. The vaginal mucosa is made of areolar …
The ovaries are paired glands fastened on either side of the uterus with the broad, suspensory, and ovarian ligaments. Each ovary features a hilum, where …
The ovarian cycle mainly consists of the follicular and the luteal phases. In the follicular phase, a primordial follicle is transformed into a primary …
Oogenesis involves the formation of egg cells, or female gametes, in the ovaries. In fetal development, diploid oogonia in the ovaries divides mitotically …
Folliculogenesis is the maturation of ovarian follicles in the ovarian cortex, essential sites for oogenesis. During fetal development,  a single …
The ovarian cycle, a monthly event in reproductive-age women, is regulated by the hypothalamic-pituitary-gonadal axis to ensure a mature oocyte is …
The uterine or fallopian tubes are 10 to 13-cm long passageways on either side of the uterus. Each tube is divided into the infundibulum, ampulla, and …
The uterus, or the womb, provides a nourishing environment for the implantation and development of a fertilized egg. It is a hollow, pear-shaped organ in …
The menstrual cycle is a sequence of monthly changes in the endometrium. The menstrual cycle may last between 21 and 38 days and is typically divided into …
The menstrual cycle starts with the menstrual phase, with its first day considered Day 1 of the cycle. This phase usually lasts for 1 to 5 days and is …
The proliferative phase is the second phase of the uterine menstrual cycle. It begins after menstruation and lasts approximately 6 to 13 days in a typical …
The secretory phase of the menstrual cycle starts after ovulation and spans from day 14 to day 28 in a typical 28-day cycle. During this period, triggered …
Premenstrual syndrome, or PMS, is a cyclical condition marked by emotional and physical distress during the postovulatory phase of the female reproductive …
Female breasts are hemispheric projections attached anteriorly to the pectoralis major and serratus anterior muscles by a dense, irregular connective …
The human embryo is bipotential, allowing the formation of either male or female reproductive organs. During the fifth week of embryonic development, the …
Puberty typically begins around ages 8 to 13 in females and 9 to 14 in males, signaling the onset of reproductive maturity. Puberty begins with bursts of …
In vitro fertilization, or IVF, is a process where eggs are fertilized with sperm in a lab and then implanted in the uterus. The process begins with …
Women's reproductive ability peaks in their 20s, after which ovarian function gradually declines, marked by a reduced response to gonadotropin …
Birth control can be achieved by three primary methods — surgical, hormonal control, and barrier methods. Vasectomy is a surgical procedure for male …
Male infertility impacts millions of couples globally. An endocrine imbalance due to hypogonadism, Klinefelter syndrome, or pituitary disorders can lead …
Female infertility is the inability to conceive after at least a year of regular unprotected intercourse, with a global prevalence of around 10%. Most …
There are several sexually transmitted infections or STIs contracted through unsafe sexual interaction. Chlamydia trachomatis, an intracellular pathogenic …
The reproductive system produces specialized cells known as gametes to conceive offspring. The gonads are the primary reproductive organs that produce …
The uterus wall has three histological layers — the perimetrium, myometrium, and endometrium. The outermost perimetrium is a thin serous membrane …
Testicular cancer, arising from spermatogenic cells, is the most common cancer in males between the ages of 20 and 35. A common symptom is the presence of …
Spermatogenesis is a unique differentiation process that ultimately gives rise to one of the most distinct cell types of the body, the sperm. …
Ovarian function progressively declines during aging and in some pathophysiological conditions including karyotype abnormality, autoimmune diseases, …
Female fertility and reproductive lifespan depend on the quality and quantity of the ovarian oocyte reserve. An estimated 80% of female germ cells …