Skeletal and Reproductive System

By:Jennifer Cholula

Function of the System

The skeletal system is made up of 206 bones and a network of tendons, ligaments, and cartilage that connects them. This systems performs support,movement,protection,blood cell production,calcium storage and endocrine regulation, which helps us move throughout the whole day.


Although a skeleton sometimes symbolizes death and creepy, scary things, it is one of the body’s most life-giving systems. Unlike other living organs, bones are firm and strong, but they have their own blood, lymphatic vessels, and nerves.

There are two types of tissue inside bones:

  • Compact bone: This hard and dense tissue makes up the outer layer of most bones and the main shaft of long bones, such as those in the arms and legs. Nerves and blood vessels live inside this tissue.
  • Spongy bone: This tissue is made up of smaller plates filled with red bone marrow. It is found at the ends of long bones, like the head of the femur, and at the center of other bones.

Red bone marrow forms most of the blood cells in the body and helps destroy old blood cells. Another type of marrow, yellow bone marrow, resides in the central cavities of long bones. It is mostly made up of fat. However, if the body suffers large amounts of blood loss, it can convert yellow marrow to red to make more blood cells.

The skull consists of 22 separate bones that make up the cranium, the housing for the brain. Twenty-one of those bones are fused together by sutures, nearly rigid fibrous joints. The lower-most bone of the skull is the mandible, or jawbone.

The spine, or vertebral column, is a series of irregularly shaped bones in the back that connects to the skull. At birth, humans have 33 or 34 of these bones. But bones fuse as we age, and the result is 26 separate bones in the spines of adults.

The rib cage is made up of 12 pairs of bones that encase vital organs in the chest. The bones curve from the back at the vertebral column to the front of the body. The upper seven pairs meet with the sternum, or chest bone. The remaining five pairs are attached to each other via cartilage or do not connect.

The muscles of the shoulders and arms include the collarbone, shoulder blade, humerus, radius, ulna, and the bones of the wrist and hand.

The hip bones are three sets of bones—ilia, ischia, and pubes—that fuse together as we grow older. These form the majority of the pelvis at the base of the spine as well as the socket of the hip joint. The sacrum—five fused bones and at the bottom of the spine—and the coccyx, or tailbone, make the rest of the bones in the pelvic region.

The head of the femur, the largest and longest bone in the body, creates the other half of the hip joint and extends down to form part of the knee. It begins the bones of the leg. The other bones of the leg include the tibia, fibula, and the bones of the ankle and foot.

Diagram of Skeletal System

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Bone Drawing

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Major Disorders

  • Osteoporosis: This is a disease in which the bones become fragile and prone to fracture.
  • Leukemia: This is a cancer of the white blood cells.

Reproductive System


  1. The purpose of the organs of the male reproductive system is to perform the following functions: To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen) To discharge sperm within the female reproductive tract during sex.


Spermatogenesis is the process of the production of sperms from the immature germ cells in males. It takes place in seminiferous tubules present inside the testes. During spermatogenesis, a diploid spermatogonium (male germ cell) increases its size to form a diploid primary spermatocyte. This diploid primary spermatocyte undergoes first meiotic division (meiosis I), which is a reductional division to form two equal haploid secondary spermatocytes. Each secondary spermatocyte then undergoes second meiotic division (meiosis II) to form two equal haploid spermatids. Hence, a diploid spermatogonium produces four haploid spermatids. These spermatids are transformed into spermatozoa (sperm) by the process called spermiogenesis.


Just like spermatogenesis, oogenesis involves the formation of haploid cells from an original diploid cell, called a primary oocyte, through meiosis. The female ovaries contain the primary oocytes. There are two major differences between the male and female production of gametes. First of all, oogenesis only leads to the production of one final ovum, or egg cell, from each primary oocyte (in contrast to the four sperm that are generated from every spermatogonium). Of the four daughter cells that are produced when the primary oocyte divides meiotically, three come out much smaller than the fourth. These smaller cells, called polar bodies, eventually disintegrate, leaving only the larger ovum as the final product of oogenesis. The production of one egg cell via oogenesis normally occurs only once a month, from puberty to menopause.

Major Disorders

Endometrosis is a condition involving colonization of the abdominal/pelvic cavity with islands of endometrial tissue. If endometrial tissue flushes up the uterine tube during menstruation and spills into the abdomen, the clots of endometrial tissue can attach to abdominal organs such as the bladder, rectum, intestinal loops and then cycle along with the uterus in response to monthly changes in ovarian hormones.

Pelvic inflammatory disease is a condition where bacteria can make their way up the vagina, through the uterus, and traverse the uterine tubes which open into the abdominal cavity.