Question

Trace the pathway of a spermatozoon (sperm cell) using words from a seminiferous tubule of the testes to the external urethral orifice. Describe the differences between a primary, secondary and Graafian follicles. Name the phases of the ovarian cycle including ovulation and indicate the main hormone produced for each one.

Answer 1

Part 1: Trace the pathway of a spermatozoon (sperm cell) using words from a seminiferous tubule of the testes to the external urethral orifice.

Sperm cells pass through a series of ducts to reach the outside of the body. After they leave the testes, the sperm passes through the epididymis, ductus deferens, ejaculatory duct, and urethra.

Epididymis

Sperm leave the testes through a series of efferent ducts that enter the epididymis. Each epididymis is a long (about 6 meters) tube that is tightly coiled to form a comma-shaped organ located along the superior and posterior margins of the testes. When the sperm leave the testes, they are immature and incapable of fertilizing ova.

Ductus deferens: The ductus deferens, also called vas deferens, is a fibromuscular tube that is continuous ( or contiguous) with the epididymis. It begins at the bottom (tail) of the epididymis then turns sharply upward along the posterior margin of the testes. Sperms are stored in the proximal portion of the ductus deferens, near the epididymis, and peristaltic movements propel the sperm through the tube.

Ejaculatory duct:

Each ductus deferens, at the ampulla, joins the duct from the adjacent seminal vesicle (one of the accessory glands) to form a short ejaculatory duct. Each ejaculatory duct passes through the prostate gland and empties into the urethra.

Urethra:

The urethra extends from the urinary bladder to the external urethral orifice at the tip of the penis. It is a passageway for sperm and fluids from the reproductive system and urine from the urinary system.

Phases of ovarian cycle:The ovarian cycle eis divided into three phases

1. Follicular phase:It is characterized with activation of up to 20 primordial follicles in order to begin the maturation process, but usually only one reaches full maturity. During this phase, the ovarian follicles mature and get ready to release an egg.

Ovulatory phase: Ovulation is the second phase of the ovarian cycle in which a mature egg is released from the ovarian follicles into the oviduct. During the follicular phase, estradiol suppresses release of luteinizing hormone (LH) from the anterior pituitary gland. When the egg has nearly matured, levels of estradiol reach a threshold above which this effect is reversed and estrogen stimulates the production of a large amount of LH. This process, known as the LH surge, starts around day 12 of the average cycle and may last 48 hours. The release of LH matures the egg and weakens the wall of the follicle in the ovary, causing the fully developed follicle to release its secondary oocyte. If it is fertilized by a sperm, the secondary oocyte promptly matures into an ootid and then becomes a mature ovum. If it is not fertilized by a sperm, the secondary oocyte will degenerate. The mature ovum has a diameter of about 0.2 mm

Luteal phase:

when Corpus luteum develops from follicular wall and produces hormones (prevalently progesterone). If fertilization does not occur and an ovum does not implant into the uterine wall, CL ( Corpus luteum ) degenerates and forms the corpus albicans (4). In case that implantation does occur, the developing placenta secretes chorionic gonadotrophin which prevents degeneration of the corpus luteum and prolongs secretion of progesterone. In humans, placenta is sufficiently developed after 5-6 weeks and then becomes the main organ of progesterone secretion.

Primary Follicle	Secondary Follicle	Graffian Follicle
A primary follicle is an immature ovarian follicle, which is surrounded by single or several layers of cuboidal granulosa cells	The secondary follicle consists of several layers of cuboidal/columnar follicular cells, now collectively called the membrana granulosa which begin to secrete follicular fluid.	The Graafian follicle is the follicular stage after the first meiotic division but before ovulation. It therefore contains a 2N haploid oocyte
As these cells enlarge they release steroid hormones called estrogens of which estradiol is the dominant one prior to ovulation.	The secondary-vesicular follicle is characterized by the presence of pockets of follicular fluid within the membrana granulosa. As the follicle continues to develop, the separate pockets fuse to form one large pocket of fluid called the follicular antrum.	It is characterized by a large follicular antrum that makes up most of the follicle