TISSUES AND SUPPORTING SYSTEMS INTRODUCTION TO THE SKELETON AND SUPPORTING TISSUES IN ANIMALS

Compiled by: Ubioka Joseph

 WEEKS 1-2: TISSUES AND SUPPORTING SYSTEMS INTRODUCTION TO THE SKELETON AND SUPPORTING TISSSUES IN ANIMALS                            Time: 40 minutes

OBJECTIVES

The students should be able to: 

I. Define skeleton and identify the types.

II. List and explain the forms of skeletons.

III. State the biological importance of skeletons.

CONTENT

Living things need the support of tissues and bones. These will enable them to maintain shape and perform some other functions such as movement and respiration.

SKELETON ANDSUPPORTINGSYSTEMS INANIMALS.

The skeleton is the bony framework of the body. In fact, the term

Skeleton comes from a Greek word meaning “Dried up.” Living bone, however, is not inert material; it is dynamic and adaptable.

BIOLOGICAL SIGNIFICANCE

1.     The skeleton and supporting tissues help the animal in going about fending for themselves.

2.     It is a measure of advancement and development as well as evolutionary position of a given organism. For instance; man stands upright with a more sophisticated skeletal build-up than a cockroach; which has an external support only.

FORMS OF SKELETON

There are 3 major forms of skeleton and these depend on: the level of development of the organism, ecological niche and habitat of the organism. The forms of skeleton are:

·        Cuticles

·        Bones and

·        Cartilages.

a.     CUTICLES: they contain waxy substance called chitin which is located externally.

b.     BONES: they are rigid tissues found in the skeletons of higher animals and are the hardest tissues in vertebrates. A bone consists of compact and spongy components and a system of canals (Harversian canal) that allows neuromuscular bundles to reach all the parts of the bone. Bone cell are known as osteocytes which are scattered and are surrounded by bony materials.

c.      CARTILAGE: they are found in the skeleton of complex vertebrates. They consist of living cells called chondrocytes, carbohydrates and protein fibers. It is tough and flexible and has great tensile strength.

Cartilages forms the skeleton in all vertebrate embryos could ossify to form bones.

Cartilages are commonly referred to as “biscuit bone”.

TYPES OF SKELETON

There are 3 main types of skeleton: namely;

Endoskeleton, exoskeleton and Hydrostatic skeleton

ü Exoskeletons are found external to the rest of the body and the tissues and organs are attached to it from inside. In arthropods, exoskeleton is made up of chitin.

ü Endoskeleton is found within the body of the organism and it is made up of cartilages and bones.

ü Hydrostatic skeleton are found in organisms that have soft bodies such as earthworms. It is made up of fluid that keeps the body turgid and maintains characteristic shape of that animal.

   

EVALUATION

1.     What is a skeleton?

2.      Differentiate between bone and cartilage?

3.     Using examples, discuss the different types of skeletons.

The bones of the skeleton perform the mechanical functions of support, protection, and leverage for body movement and the metabolic functions of hemopoiesis and storage of fat and minerals. The strength of bone comes from its inorganic components, of such durability that they resist decomposition even after death. It performs many body functions, including support, protection, and leverage for body movement, hemopoiesis in the red bone marrow, fat storage in the medullary cavity, and mineral storage.

1.     Support: The skeleton forms a rigid framework to which the softer tissues and organs of the body are attached. It is of interest that the Skeleton’s 206 bones support a mass of muscles and organs that may weigh 5 times as much as the bones themselves.

2.     Protection:  The skull and vertebral column enclose the brain and spinal cord; the rib cage protects the heart, lungs, great vessels, liver, and spleen; and the pelvic girdle supports and protects the pelvic viscera. Even the sites where blood cells are produced are protected within the spongy bone tissue of certain bones.

3.     Body movement: Bones serve as anchoring attachments for most skeletal muscles. In this capacity, the bones act as levers (with the joints functioning as pivots) when muscles contract and cause body movement. One of the most important types of body movements includes the

respiratory movements.

These will permit mammals to breathe efficiently by the action of the Diaphragm, intercostal muscles and the rib cage.

4.     Hemopoiesis: The process of blood cell formation is called hemopoiesis ( hem''o˘-poi-e'sis). It takes place in tissue called red bone marrow located internally in some bones. It is estimated that an average of 2.5 million red blood cells are produced every second by the red bone marrow to replace those that are worn out and destroyed by the liver.

5.     Fat storage: Lipid is stored in the adipose tissue within the medullary cavity of certain bones. The adipose tissue and its lipid content are known as yellow bone marrow

6.     Mineral storage: The inorganic matrix of bone is composed primarily of the minerals calcium and phosphorus. These minerals which account for approximately two-thirds of the weight of bone, give bone its firmness and strength. About 95% of the calcium and 90% of the phosphorus within the body are deposited in the bones and teeth. Although the concentration of these inorganic salts within the blood is kept within narrow limits, both are essential for other body functions. Calcium is necessary for muscle contraction, blood clotting, and the movement of ions and nutrients across cell membranes. Phosphorus is required for the activities of the nucleic acids DNA and RNA, as well as for ATP utilization. If mineral salts are not present in the diet in sufficient amounts, they may be withdrawn from the bones until they are replenished through proper nutrition. In addition to calcium and phosphorus, lesser amounts of magnesium, sodium, fluorine, and strontium are stored in bone tissue.

EVALUATION

I.                    State some characteristics of bones?

II.                 What are the functions of the skeletal system?