


Chapter 6: Support systems in animals

6.1 Overview (ESG7Y)

This chapter begins by introducing the different basic skeletal types in animals. The link between skeletal structure and function is explored by examining advantages and disadvantages of each skeleton type; and by linking the different skeletal types to various evolutionary adaptations that took place over time.

The majority of the chapter focuses on the musculoskeletal systems of humans. There is a large focus on understanding the anatomy of the human skeleton in some detail. This is followed by a broad overview of the other components of the musculoskeletal system, such as cartilage, joints, tendons, ligaments and muscles. The structure of muscles, and their organisation into antagonistic pairs, will be covered using the biceps- triceps antagonistic pair as an illustrative example. The chapter ends with an overview of some common diseases affecting the musculoskeletal system.

Introduction (ESG7Z)

In this chapter we will be studying the different types of skeletal structures. We will focus in particular on the human skeleton. In Grade 12 you will come to know how our skeletal structure evolved. For now, you will be introduced to the main features and functions of the human skeleton. By focusing on specific structures of the human skeleton, we once more emphasise a common theme of our study of Life Sciences: that structure is related to function.

  • Some of the main types of skeleton found in living things are the hydrostatic skeleton, endoskeleton and exoskeleton. Each of these skeletal types have advantages and disadvantages.
  • Skeletal structures are adapted for the transition from an aquatic to a terrestrial existence where greater support was required.
  • The human skeleton consists of the axial skeleton and the appendicular skeleton.
  • The main functions of the skeleton are to allow for movement, provide protection, provide support, store minerals, produce blood cells and allow for hearing.
  • It is important to understand the relationship between structure and function of bones, cartilage, tendons and ligaments.
  • Joints connect pieces of skeleton and allow independent movement of neighbouring pieces. Joints are of three types: fixed, partly movable and freely movable (synovial joints). Synovial joints are of either ball-and-socket, hinge, pivot, or gliding structure.
  • Skeletal muscle is attached to the skeleton through tendons and ligaments. The structure of voluntary skeletal muscle is made up mainly of myofibrils which allow for muscle contraction. This contraction is used to move part of the skeleton.
  • Diseases affecting the skeleton include rickets in children, and osteoporosis and arthritis in adults.