7 Support systems in animals
7.1 Overview
Introduction DUMMY
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: thatstructureis related to
function.Key concepts- Some of the main types of skeleton found in living things are the hydrostatic skele-
ton, 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 struc-
ture 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 arthri-
tis in adults.
7.2 Skeletons
The skeleton is the supporting structure of an organism. There are three different types of
skeletons: hydrostatic skeletons, endoskeletons and exoskeletons.- Hydrostatic skeleton: water exerts pressure on muscular walls, for example, in jelly-
fish. - Exoskeleton: the stable chitinous or mineralised outer shell of an organism, for exam-
ple, the shell of a grasshopper or prawn.
190 7.1. Overview