Microbial Diseases of the Genitourinary System

Overview of the Male and Female Reproductive Systems

The human reproductive system functions to produce human offspring, with the male providing sperm and the female providing the ovum.

Learning Objectives

Summarize the reproductive systems of men and women

Key Takeaways

Key Points

  • The male reproductive system consists of external organs. The testes in the scrotum produce the male gamete, sperm, which is ejaculated in seminal fluid by the penis.
  • The female reproductive system primarily consists of internal organs. The female gamete, ovum, is produced in the ovaries and is released monthly to travel to the uterus via the Fallopian tubes.
  • Fertilization can occur if the penis is inserted through the vulva into the vagina and sperm is ejaculated towards the cervix. If an ovum is currently in the uterus, it can then be fertilized by sperm that manage to enter the cervix.
  • Once fertilized, an ovum becomes a zygote and if all goes well, develops into a fetus in the uterus.
  • Natural birth occurs when the fetus is pushed from the vagina after nine months in the uterus.

Key Terms

  • fallopian tubes: The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges (singular salpinx) are two very fine tubes lined with ciliated epithelia leading from the ovaries of female mammals into the uterus, via the utero-tubal junction.
  • penis: The male sexual organ for copulation and urination; the tubular portion of the male genitalia (excluding the scrotum).
  • vagina: A fibromuscular tubular tract which is the female sex organ and has two main functions: sexual intercourse and childbirth.

The reproductive system or genital system is a set of organs within an organism that work together to produce offspring. Many non-living substances, such as fluids, hormones, and pheromones, are important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals and thus the possibility of greater genetic fitness of the offspring.

The Reproductive Process

Human reproduction takes place as internal fertilization by sexual intercourse. During this process, the erect penis of the male is inserted into the female’s vagina until the male ejaculates semen, which contains sperm, into the vagina. The sperm travels through the vagina and cervix into the uterus for potential fertilization of an ovum. Upon successful fertilization and implantation, gestation of the fetus occurs within the female’s uterus for approximately nine months (pregnancy). Gestation ends with labor resulting in birth. In labor, the uterine muscles contract, the cervix dilates, and the baby passes out through the vagina. Human babies and children are nearly helpless and require high levels of parental care for many years. One important type of parental care is the use of the mammary glands in the female breasts to nurse the baby.

The Male Reproductive System

The human male reproductive system is a series of organs located outside of the body and around the pelvic region. The primary direct function of the male reproductive system is to provide the male gamete or spermatozoa for fertilization of the ovum. The major reproductive organs of the male can be grouped into three categories. The first category is sperm production and storage. Production takes place in the testes, housed in the temperature-regulating scrotum. Immature sperm then travel to the epididymis for development and storage. The second category, the ejaculatory fluid-producing glands, includes the seminal vesicles, prostate, and vas deferens. The final category, used for copulation and deposition of the spermatozoa (sperm) within the female, includes the penis, urethra, vas deferens, and Cowper’s gland.

This diagram of the male reproductive organs indicates the bladder, pubic bone, penis, corpus cavernosum, penis glands, foreskin, urethral opening, scrotum, testis, epididymis, vas deferens, anus, Cowper's gland, prostate gland, ejaculatory duct, seminal vesicle, rectum, and sigmoid colon.

The Human Male Reproductive System: Cross-sectional diagram of the male reproductive organs.

Only our species has a distinctive mushroom-capped glans, which is connected to the shaft of the penis by a thin tissue of frenulum (the delicate tab of skin just beneath the urethra). One of the most significant features of the human penis is the coronal ridge underneath the gland around the circumference of the shaft. Magnetic imaging studies of heterosexual couples having sex reveal that during coitus, the typical penis expands to fill the vaginal tract, and with full penetration can even reach the woman’s cervix and lift her uterus. This combined with the fact that human ejaculate is expelled with great force and considerable distance (up to two feet if not contained), suggests that men are designed to release sperm into the uppermost portion of the vagina. This may be an evolutionary adaptation to expel the semen left by other males while at the same time increasing the possibility of fertilization with the current male’s semen.

The Female Reproductive System

This diagram of the female reproductive system indicates the Fallopian tube, bladder, G-spot, clitoris, pubic bone, urethra, vagina, ovary, sigmoid colon, fornix, cervix, rectum, and anus.

The Human Female Reproductive System: The female reproductive system is largely internal.

The human female reproductive system is a series of organs primarily located inside the body and around the pelvic region. It contains three main parts: the vagina, which leads from the vulva, the vaginal opening, to the uterus; the uterus, which holds the developing fetus; and the ovaries, which produce the female’s ova. The breasts are also a reproductive organ during parenting, but are usually not classified as part of the female reproductive system. The vagina meets the outside at the vulva, which also includes the labia, clitoris, and urethra. During intercourse, this area is lubricated by mucus secreted by the Bartholin’s glands. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the Fallopian tubes. At certain intervals, approximately every 28 days, the ovaries release an ovum that passes through the Fallopian tube into the uterus.

If the ova is fertilized by sperm, it attaches to the endometrium and the fetus develops. In months when fertilization does not occur, the lining of the uterus, called the endometrium, and unfertilized ova are shed each cycle through a process known as menstruation.

Overview of the Urinary System

The urinary system maintains blood homeostasis by filtering out excess fluid and other substances from the bloodstream and secreting waste.

Learning Objectives

Review the urinary system

Key Takeaways

Key Points

  • The renal system eliminate wastes from the body, controls levels of electrolytes and metabolites, controls the osmoregulation of blood volume and pressure, and regulates blood pH.
  • The renal system organs include the kidneys, ureter, bladder, and urethra. Nephrons are the main functional component of the kidneys.
  • The respiratory and cardiovascular systems have certain functions that overlap with renal system functions.
  • Metabolic wastes and excess ions are filtered out of the blood, combined with water, and leave the body in the form of urine.
  • A complex network of hormones controls the renal system to maintain homeostasis.

Key Terms

  • ureter: These are two long, narrow ducts that carry urine from the kidneys to the urinary bladder.
  • osmoregulation: The most important function of the renal system, in which blood volume, blood pressure, and blood osmolarity (ion concentration) is maintained in homeostasis.

The Renal System

The renal system, which is also called the urinary system, is a group of organs in the body that filters out excess fluid and other substances from the bloodstream. The purpose of the renal system is to eliminate wastes from the body, regulate blood volume and pressure, control levels of electrolytes and metabolites, and regulate blood pH.

The renal system organs include the kidneys, ureters, bladder, and urethra. Metabolic wastes and excess ions are filtered out of the blood, along with water, and leave the body in the form of urine.

This is an illustration of the major organs of the renal system. In this schematic view of the urinary system, shown in descending order, we see the kidney, ureter, bladder, and urethra.

Components of the renal system: Here are the major organs of the renal system.

Renal System Functions

TheĀ  renal system has many functions. Many of these functions are interrelated with the physiological mechanisms in the cardiovascular and respiratory systems.

  1. Removal of metabolic waste products from the body (mainly urea and uric acid).
  2. Regulation of electrolyte balance (e.g., sodium, potassium, and calcium).
  3. Osmoregulation controls the blood volume and body water contents.
  4. Blood pressure homeostasis: The renal system alters water retention and thirst to slowly change blood volume and keep blood pressure in a normal range.
  5. Regulation of acid-base homeostasis and blood pH, a function shared with the respiratory system.

Many of these functions are related to one another as well. For example, water follows ions via an osmotic gradient, so mechanisms that alter sodium levels or sodium retention in the renal system will alter water retention levels as well.

Organs of the Renal System

Kidneys and Nephrons

Kidneys are the most complex and critical part of the urinary system. The primary function of the kidneys is to maintain a stable internal environment (homeostasis) for optimal cell and tissue metabolism. The kidneys have an extensive blood supply from the renal arteries that leave the kidneys via the renal vein.

Nephrons are the main functional component inside the parenchyma of the kidneys, which filter blood to remove urea, a waste product formed by the oxidation of proteins, as well as ions like potassium and sodium. The nephrons are made up of a capsule capillaries (the glomerulus) and a small renal tube.

The renal tube of the nephron consists of a network of tubules and loops that are selectively permeable to water and ions. Many hormones involved in homeostasis will alter the permeability of these tubules to change the amount of water that is retained by the body.

Ureter

Urine passes from the renal tube through tubes called ureters and into the bladder.

Bladder

The bladder is flexible and is used as storage until the urine is allowed to pass through the urethra and out of the body.

Urethra

The female and male renal system are very similar, differing only in the length of the urethra.

Human Osmoregulation

The kidneys play a very large role in human osmoregulation by regulating the amount of water reabsorbed from the glomerular filtrate in kidney tubules, which is controlled by hormones such as antidiuretic hormone (ADH), renin, aldosterone, and angiotensin I and II.

A basic example is that a decrease in water concentration of blood is detected by osmoreceptors in the hypothalamus, which stimulates ADH release from the pituitary gland to increase the permeability of the wall of the collecting ducts and tubules in the nephrons. Therefore, a large proportion of water is reabsorbed from fluid to prevent a fair proportion of water from being excreted.

The extent of blood volume and blood pressure regulation facilitated by the kidneys is a complex process. Besides ADH secretion, the renin-angiotensin feedback system is critically important to maintain blood volume and blood pressure homeostasis.

Normal Genitourinary Microbiota

The vaginal microflora consist mostly of various lactobacillus species.

Learning Objectives

Recognize the types of bacteria present in the vaginal microflora

Key Takeaways

Key Points

  • If microbe numbers grow beyond their typical ranges (often due to a compromised immune system) or if microbes populate atypical areas of the body (such as through poor hygiene or injury), disease can result.
  • Disturbance of the vaginal flora can lead to bacterial vaginosis.

Key Terms

  • urinary tract infection: Finding bacteria or other microorganisms, such as yeasts, in bladder urine with or without clinical symptoms and with or without renal disease.

The Genitourinary Microbiome

The human microbiome, or human microbiota, is the aggregate of microorganisms that reside on the surface and in deep layers of skin, in the saliva and oral mucosa, in the conjunctiva, and in the gastrointestinal tracts. They include bacteria, fungi, and archaea. Some of these organisms perform tasks that are useful for the human host. However, the majority have no known beneficial or harmful effect. Those that are expected to be present and that under normal circumstances do not cause disease, but instead participate in maintaining health, are deemed members of the normal flora.

Populations of microbes inhabit the skin and mucosa. Their role forms part of normal, healthy human physiology; however, if microbe numbers grow beyond their typical ranges (often due to a compromised immune system) or if microbes populate atypical areas of the body (such as through poor hygiene or injury), disease can result.

Proportions of Microbes

It is estimated that 500 to 1000 species of bacteria live in the human gut and a roughly similar number on the skin. Bacterial cells are much smaller than human cells, and there are at least ten times as many bacteria as human cells in the body (approximately 1014 versus 1013). Normal flora bacteria can act as opportunistic pathogens at times of lowered immunity.The vaginal microflora consist mostly of various lactobacillus species. It was long thought that the most common of these species was Lactobacillus acidophilus, but it has later been shown that the most common one is L. iners followed by L. crispatus. Other lactobacilli found in the vagina are L. jensenii, L. delbruekii and L. gasseri. Disturbance of the vaginal flora can lead to bacterial vaginosis.

image

Lactobacillus: Lactobacilli and a vaginal squamous cell.