1. DIFFERENT TYPES OFSKELETONSThe three main types of skeletonsare:Hydrostatic skeletons (lack hardparts)Exoskeletons (external hard parts)Endoskeletons (internal hard parts)
Hydrostatic SkeletonsA hydrostatic skeleton consists of fluidheld under pressure in a closed body This is the main type of skeleton inmostcnidarians, flatworms, nematodes, andannelidsAnnelids use their hydrostatic skeletonfor peristalsis, a type of movement onland produced by rhythmic waves ofmuscle contractions.
ExoskeletonsAn exoskeleton is a hardencasement deposited on thesurface of an animalExoskeletons are found in mostmolluscs and arthropodsArthropod exoskeletons are madeof cuticle and can be both strongand flexibleThe polysaccharide chitin is oftenfound in arthropod cuticle
ENDOSKELETONSAn endoskeleton consists of hardsupporting elements, such asbones, buried in soft tissueEndoskeletons are found insponges, echinoderms, andchordatesA mammalian skeleton has more than200 bonesSome bones are fused; others areconnected at joints by ligaments thatallow freedom of movement.
a. AXIAL SKELETON: i)Human Skull Consist of 28 bones It consists of flat bones that are connectedon the sides by immovable joints calledsutures. In babies not all the bones of the skull makecontact with each other and fontanels areformed. The lower jaw bone (Mandible) is the onlymovable bone of the skull – Upper jaw(Maxilla) is not moveable. The large opening at the base of the skull iscalled the foramen magnum – it is where thespinal cord enters the skull.
a. AXIAL SKELETON: ii)VERTEBRAL COLUMN Consists of 33 bones called vertebrae. 24 vertebrae are individual single bones. 9 vertebrae are fused to form the sacrum andcoccyx. Cartilage disks are found between vertebrae. The s-shaped structure of the vertebral columnand the disks absorb shock and help toprotect the spinal cord. The first vertebrae – Atlas – carry the weight ofthe skull, allows the head to nod. 2nd vertebrae – Axis – allows head to move tothe side
a. AXIAL SKELETON: iii) THORAX Consists of the sternum, 12 pairs of ribs andthoracic vertebrae. It protects the heart and lungs. First 7 pairs of ribs are directly attached to thesternum by cartilage – called true ribs. Next 5 pairs – false ribs – last 2 pairs of falseribs are not attached to the sternum – calledfloating ribs Intercostal muscles found between ribs – aidin breathing process.
a. AXIAL SKELETON: iii) THORAXTrue ribsFalse ribs Floating ribssternum
b. APPENDICULAR SKELETONMade up of the shoulder (pectoralgirdle), arms, hips (pelvic girdle) and legs.126 bones.Function: Movement
b. APPENDICULAR SKELETON i) Pectoral girdleand arm
b. APPENDICULAR SKELETON i) Pelvic girdle andleg
3. FUNCTIONS OF A SKELETON Support Movement Protection Blood cell production Storage Endocrine regulation
a. Support The skeleton provides theframework which supports the bodyand maintains its shape. The pelvis, associated ligamentsand muscles provide a floor for thepelvic structures. Without the ribs, costalcartilages, and intercostalmuscles, the heart would collapse.
b. MOVEMENT The joints between bones permitmovement. Movement is powered by skeletalmuscles, which are attached to theskeleton at various sites on bones. Muscles, bones, and joints providethe principal mechanics formovement, all coordinated by thenervous system.
c. ProtectionThe skeleton protects many vitalorgans e.g.: The skull protects the brain, theeyes, and the middle and innerears. The vertebrae protects the spinalcord. The rib cage, spine, and sternumprotect the lungs, heart and majorblood vessels.
d. Blood cell production• The skeleton is the site ofhaematopoiesis, which takesplace in red bone marrow.• Haematopoiesis is the formation ofblood cellular components.
e. Storage• Bone matrix can store calciumand is involved in calciummetabolism.• The bone marrow can store ironand is involved in iron metabolism.• Bones are not entirely made ofcalcium, but a mixture ofchondroitin sulfate andhydroxyapatite, the latter makingup 70% of a bone.
f. Endocrine regulation• Bone cells release a hormonecalled osteocalcin, whichcontributes to the regulation ofblood sugar (glucose) and fatdeposition.• Osteocalcin increases both theinsulin secretion and sensitivity.
4. STRUCTURE OF A LONGBONEA long bone is an elongated boneconsisting of a body (diaphysis) andtwo terminal parts(epiphyses), such as found in theleg and arm bones(femur, radius, phalanges andothers).
5. DIFFERENT JOINTS In the human body, there are jointswhere two or more bones meet in theskeleton. Immovable joints do not allowmovement and Synovial joints are movevable jointsand allow movement of the bones. Ligaments hold bones together. Tendons attach muscle to bone,.
Different types of synovial joints are:• Ball and socket joint• Hinge joint• Pivot joint• Gliding joint
BALL AND SOCKET JOINT:• Joints of the hips and shoulders• Allows rotating movement of armsand legs
HINGE JOINT:• Joints of the elbows, knees, fingersand toes• Only allows movement in onedirection.
PIVOT JOINT:• Joints between atlas and axis• One bone turns on another
GLIDING JOINT:• Joints of the wrist and ankles• The flat surface of one bone glidesover the surface of a bone next toit.
JOINT DISORDERSDo research (self study) on the followingdisorders, you have to be able to brieflyexplain what each of them are (will notbe marked but there will be question inthe exam and semester test about it) Dislocation Sprains Arthritis Osteoarthritis Rheumatoid arthritis
SKELETAL MUSCLES Muscles are attached to bones bymeans of tendons. Skeletal muscles produce movementby contracting. This exerts a force on tendons, whichin return, pulls on bones. Muscles occur in pairs which workantagonistic against each other. When one contracts the other relaxes.