Measurable Outcomes

• Analyze reproductive and urinary organ tissues under the microscope.
• Complete the dissection of the kidney and accurately identify (with a pin) all structures of the kidney using the corresponding vocabulary list.
• Learn about the organs of the urinary system: kidney, ureter, urinary bladder and urethra, as well as the structural elements of the nephron and label on any available models.
• Compare and contrast the elements of the male and female reproductive systems and their associated accessory glands.
• Recognize homologous structures of the male and female reproductive systems.
• Demonstrate an adequate understand of the material in this section.

Background

The urinary system is one of excretion, elimination and reabsorption. It is made from four organs, only one of which produces urine (the kidney). Nephrons, the smallest functional unit of the kidneys, are found in numbers of one to two million within the kidney and can filter up to 400 gallons of cycled blood, daily. The kidneys receive more blood than the heart, liver, or even the brain and have vital functions such as the regulation of pH, blood pressure, concentration of blood solutes and concentration of red blood cells. The remaining three organs (ureters, urinarybladder, and urethra) facilitate urine storage and secretion. Of these organs, only the urethra is anatomically distinct between males and females.

The reproductive system is designed to propagate a species and therefore has two primary functions: the production of gametes (n) and sex hormones.  Male gametes are referred to as sperm cells, whereas female gametes are called ova. Reproduction is very metabolically taxing especially for the female. To illustrate, mature ovum can contain as many as 600,000 mitochondria; to reference, liver cells and cardiac muscles cells contain 2,000 and 5,000 mitochondria respectively. The role of the male reproductive system is to produce sperm and transfer them to the female reproductive tract. Although they originate from similar primordial tissues, the female and male reproductive systems differ in gonad type, ducts, accessory glands, and external genitalia. Male gonads are referred to as testes while the female gonads as ovaries; both are the sites of their respective gametogenesis. The hormones produced by the gonads are crucial to the reproductive system and sexual development, including primary and secondary sexual development, tissue regeneration, and production of gametes.

Humans are a sexually dimorphic species, which mean that there are distinguishing secondary sex characteristics. The hormones that influence male primary and secondary sexual development are called androgens. The hormones that influence female primary secondary sexual development are called estrogens. In females, this entails the development of breasts which are specialized sweat glands.  Males also have mammary tissue but their development is arrested early. Similarly, the thyroid cartilage is enlarged and commonly referred to as an Adam’s apple in males but not so in females.

A developing fetus remains anatomically undifferentiated a will either develop characteristically male or female anatomy. At some point of gestation, the fetus will develop both Wolffian and Müllerian ducts, anlagen of the male and female reproductive systems. As a result, there are several elements of the male and female reproductive systems which are homologous.  Such structures share developmental and evolutionary origins but are not necessarily similar in function. The following are the homologous structures of the male and female reproductive system: labia majora – male scrotum; labia minora – shaft of penis; clitoris – glans penis; paraurethral gland – prostate gland; greater vestibular gland – bulbourethral gland.

Vocabulary for the Urinary and Reproductive systems on page(s) 172 and 168.