Comparing Ovaries and Testes Reproduction is the process by which offspring are produced. Humans reproduce sexually. Gametes are produced in specialized sex organs. In the human male, testes produces sperm cells which are the male gametes, as well as producing the male hormone, testosterone. In the human female, the two ovaries produce egg cells which are the gametes, as well as secreting estrogen and progesterone.

Procedure Part A: The Human Ovary Materials: microscope, prepared slides of human ovary, testes and sperm, paper, color pencils, pencil, circle template Procedure Part A: The Human Ovary 1. Obtain a human ovary slide. Using the low-power objective, focus on a part of the ovary where you can see both the outer edge and the interior of the ovary. The outermost layer of consists of a single layer of epithelial cells. Immediately below this layer in the interior of the ovary, you will observe numerous round structures of various sizes. These structures are the follicles, in which the eggs develop and mature. In some of the follicles you will observe the developing egg, a large, circular cell with a darkly stained nucleus.

Procedure Part B: The Human Testis 1. Obtain a human testis slide and examine on low power. The testis has a thick outer covering and is separated into several wedge-shaped compartments by partitions. Within each compartment examine the cluster of small circles. These are the cut surfaces of the tiny, coiled seminiferous tubules. The seminiferous tubules lead into the epididymis, a long, narrow, flattened structure attached to the surface of the testis. Sperm complete their maturation while passing through the epididymis. The lower portion of the epididymis uncoils and widens into a long duct called the vas deferens.

Switch to the high-power objective and focus on the seminiferous tubules. Notice that the walls consist of many layers of cells. The cytoplasm of these cells will be stained red and the chromosomes in the nuclei will be stained blue. Closely examine these cells in order to trace the various stages of sperm production. The cells undergo meiosis from the outer layer of the tubule toward the inside where they are released. Try to locate some mature sperm with flagella in the center of a seminiferous tubule.

Procedure Part C: The Human Sperm Obtain a human sperm slide, begin on low-power then use the highest power objective. Sperm cells are the smallest of human cells, no more than a nucleus with some cytoplasm, some mitochondria and a long tail. Patiently focus until you get the clearest view of one sperm cell. The head of the sperm contains 23 chromosomes and has a dome-shaped acrosome at the tip. The acrosome contains enzymes to enable the sperm to fertilize the ovum. The middle is packed full of mitochondria that provide energy to propel the flagella

Comparing Ovaries and Testes Data Sheet Part A. The Human Ovary 1. Complete the missing labels a. b.

Part B: The Human Testis 1. Complete the missing labels: c. d. b. a.

Part C. The Human Sperm 1. Complete the missing labels. c. a. b.

Part D. Analysis 1. In what way are mature sperm and egg cells different from all other types of body cells? 2. Describe the stages of development of the follicles in the ovarian tissue. 3. Considering some mammals give birth to litters rather than single offspring, how does ovulation differ from that in humans? 4. Describe the difference in size and structure of an ovum and a sperm.