The Facts of Life: Examining Reproductive Health

Anatomy

This image shows a cross section through the many seminiferous tubules shown in the first figure. Inside each tubule are clusters of round cells that are immature sperm. As they mature and develop, they move towards the center hollow portion of the tube where they acquire tails.

4. Variants of Human Spermatozoa 1931

A seminiferous tubule is cut open and shown at high magnification in this figure. The youngest, most immature sperm are located at the peripheral margin of the tubule and are called spermatogonia. These immature sperm either continually divide to renew the population of developing sperm or they mature to become sperm with tails. Mature sperm are situated in the center lumen of the tubule. Many long tails of mature sperm are seen in the center hollow portion of this tube.

Shown are details of a mature sperm which consist of a head region, appearing flattened in the human, and the tail which propels the sperm.

5. Drawing of Human Spermatozoa
1694
The drawing was conceived by Niklaas Hartsoeker not by what
he had seen, but what he presumed would be visible if sperm
could be adequately viewed.

After maturation, millions of sperm within the testis pass through a series of smaller tubes into the large excretory duct of the male reproductive system called the epididymis. The epididymis, shown here, is a highly coiled tube. It is cut across revealing the lumen or hollow portion of the tube at many locations along its length. At the top right of the figure can be seen bundles of mature sperm exposed in their passage along a cut-open portion of the tube.

The exposed portion of the epididymis shown in Figure 6 is photographed at higher magnification here. The wall of the tube contains a lining of cells called the epithelium and this is in turn, surrounded on its outer surface by a special layer of smooth muscle that contracts to produce waves of peristalsis, helping to propel these mature sperm along its length. Many mature sperm with long tails are bunched together in the center of this tube.

This scanning electron micrograph shows a low magnification view into one of the excretory glands of the male reproductive system called the seminal vesicle. The inside of the seminal vesicle reveals large out-pocketings formed by creases and folds of its inner lining. The seminal vesicle produces the thick liquid portion of semen.

Shown is a low magnification view of the ovary cut open to expose its internal organization. In the upper left corner, the oviduct or tube carrying eggs from the ovary is cut across its coiled length. Many developing eggs at different stages of maturity are seen within the ovary, as spheres of organized tissue. After the eggs have been shed or ovulated, the remaining tissue called the corpus luteum, remains to produce female hormones.

This figure shows the outer surface of the ovary containing a layer of cells that have small micro-projections of their membrane called microvilli. These appear as short, thin projections from the surface of the cell. The small, round bulges represent the underlying nucleus of each cell.

A cluster of maturing eggs are shown in this micrograph from inside the ovary. As the egg matures, multiple layers of cells form.

This micrograph shows a high magnification view of a mature egg (follicle) cut open before it is released from the ovary. The germ cell or primary egg is located in the center of this follicle and was removed during preparation to leave a hole in the surrounding layer of tissue that surrounded the egg, which appears folded. Surrounding the germ cell are multiple layers of follicle cells which produce hormones and nourishment for the developing egg. These cells produce a lake of fluid which is also seen as the smooth surface in the center of this mature follicle. A period of 10 to 14 days is required for a follicle to reach full maturity in the human at which time it may be 10 millimeters or more in diameter.

The blood supply of the ovary is shown in this image. A liquid plastic was injected into the artery supplying the ovary; the plastic filled all of the blood vessels and veins draining the ovary. After the plastic hardens, the tissue is digested away leaving a microvascular cast of the entire circulation of the ovary. Major arteries and veins supplying and draining blood are seen with their branches coming up from the lower right portion of the photograph. An extensive network of capillary blood vessels is seen for individual follicles that are developing and maturing, as well as for the corpora lutea, which remain to produce hormones after the egg is shed from the surface of the ovary. These appear as clusters of large, round, spherical, microvascular structures in the lower half of this micrograph.

The fallopian tube, or oviduct, conveys the ovulated egg from the ovary to the uterus. In this image, a cut through the wall of the oviduct shows the many finger-like folds of the wall which is lined by a single layer of tall columnar-like cells making up the inner lining. In the outer wall are bands of smooth muscle that help the oviduct contract to move the egg along its surface.

A further close-up of the surface of the inner layer of the oviduct shows the tall column-like cells of the epithelium. Two types of cells are seen: a secretory cell and a ciliated cell. The secretory cell produces a mucus substance and appears smooth on its surface. The ciliated cells have long motile hairs, called cilia, that help propel the egg and secretions along the inner surface of the oviduct using a beating motion.

An even higher magnification view of the surface of the lining of the oviduct shows the secretory and ciliated cells side-by-side. Many secretory cells have small projections of their membrane called microvilli. The adjacent ciliated cells have organized motile hair called cilia which beat to move the secretion and egg along its path.

A cut through the wall of the uterus is shown. The uterine wall is composed of an inner layer called the endometrium, which contains the surface lining and glands, and the outer portion, or myometrium, which contains blood vessels and smooth muscle which helps the uterus to contract. The holes and spaces in the middle of the uterine wall represent blood vessels which were cut open along this plane.

This low power view of the uterus reveals the hollow space in the center called the lumen. The folded inner surface or endometrium is distinguished by the many uterine glands which open onto its surface and appear as small holes along the lumenal surface. The thicker myometrium contains the muscle of the uterus and blood vessels which appear as dark spaces in the outer portion of its wall.

A higher magnification view of a cut through the uterine wall is shown here. The many small holes opening into the lumen of the uterus represent the uterine glands which secrete a mucus substance.

A close-up of an opening into a uterine gland is shown here.

A cast of the uterine circulation is shown in this picture after the tissue was digested away leaving the plasticized skeleton of the circulation. The largest vessels in the center of the wall branch inward to supply the endometrium and also branch outward to supply the muscle coat or myometrium of the uterine wall.

The cervix or lower extension of the uterus is shown in low magnification. It is partially cut open to reveal the cervical canal which opens into the vagina. The inner lining of the cervix or endocervix is extensively folded and long tubular glands open from the wall into the cervical canal. The outer wall of the cervix appears smooth and contains layers of muscle.

Several of the furrows and folds of the inner lining of the cervix are shown here at higher magnification. The surface, shown at higher magnification in the adjacent figure, appears as a cobblestone organization of many tall cells which are either secretory or ciliated, similar to the uterus.

The surface of the cells lining the cervix is shown at higher magnification to reveal their brush-like border consisting of many micro-projections called microvilli. Interspersed are other cells which have longer motile hairs, or cilia.

The vagina is shown in low magnification in a cross-section view. It is a fibromuscular tube consisting of an inner mucosal layer, a middle muscular layer and an outer layer of connective tissue.

The inner surface of the vaginal wall appears folded in this image. The lining cells are epithelium consists of multi-stratified layers. These cells become flattened on the surface and are continuously shed as they are replaced by newly-formed cells underneath.

A higher magnification view shows the flattened cells on the inner surface of the vaginal wall that are continually being shed.

Male Reproductive System
Male sex organs are located both within and ouside the body. The primary external organs for reproduction are the testes which produce male sex cells (spermatozoa). Accessory organs consist of sex glands, external reproductive organs, and a series of ducts that carry spermatozoa from the testes to the exterior of the body.

ANATOMY
Penis: The penis is the organ which ejaculates sperm during sexual intercourse. When sexually stimulated, blood is pumped into the tissues of the penis which causes an erection.

Urethra: The urethra extends from the bladder to the tip of the penis. Its upper part connects to the vas deferens. Both urine and semen are passed through this tube to the exterior of the body.

Scrotum: This sac-like pouch houses two testicles.

Testicles: The testicles are oval-shaped organs that produce sperm, the hormone testosterone, and about 5% of the seminal fluid. On average, a healthy man can produce up to 100 million sperm every day (about 1,000 sperm per second.) Testosterone is the hormone which lowers the pitch of a man's voice and stimulates muscle and bone growth in an adolescent male.

Vas deferens: This long tube carries mature sperm from the testicles to a seminal vesicle positioned behind the bladder. The vas deferns joins with the seminal vesicle to form an ejaculatory duct.

Epididymis: Lying on top of the testicle, this coiled tube stores mature sperm until they are passed into the vas deferns.

Seminal vesicle: Located behind the bladder and on top of the vas deferens, the two seminal vesicles supply 60% of the seminal fluid.

Prostate gland: This gland, surrounding the upper part of the urethra, provides about 30% of the seminal fluid.

Bulbourethral glands: 5% of the seminal fluid is produced in these glands located on either side of the base of the penis.