The Skeletal System

1. The Skeletal System • Skeletal and muscle systems work together and are controlled by our nervous system

2. 3 types of muscle • Skeletal muscle • associated with the skeleton • it tires easily (open and close your fist for 2 minutes!) • This muscle is under conscious control - voluntary

3. 2. Smooth muscle – also called unstriped or involuntary muscle • Found internally in digestive system, bladder, blood vessels, uterus etc. • Contracts slowly • Slow to tire • Not under conscious control

4. 3. Cardiac muscle • Found in the heart • Involuntary • Contracts strongly • Does not tire

5. Types of Skeleton • Exoskeleton – skeleton on the outside Eg. Insects • Endoskeleton – skeleton on the inside Eg. Humans

6. What type of skeleton is in each of the following?? • Lobster • Rabbit • Elephant • Beetle • Crab • Fish

7. Answers • Lobster - Exoskeleton • Rabbit – Endoskeleton • Elephant - Endoskeleton • Beetle - Exoskeleton • Crab - Exoskeleton • Fish - Endoskeleton

8. Functions of the skeleton • Support • Shape • Protection • Movement • Manufacture of blood components

9. Support • Skelton provides a rigid frame to hold body upright

10. Shape • Person with long bones will be tall • Bones in the foot determine the width of the foot etc

11. Protection • Skull protects brain • Spine protects spinal chord • Ribs protect heart + lungs

12. Movement • Bones act as rigid levers against which muscles pull

13. Manufacture of blood components • Bone marrow makes red blood cells, white blood cells and platelets

14. Structure of the skeleton • 213 bones in total • Divided into Axial and Appendicular skeleton

16. Axial skeleton • Consists of Skull , Spine, ribs and sternum

17. Skull • Also called the cranium • Consists of 22 bones • Most are fused together • Lower jaw moves to allow mouth to open and close

18. Made of 33 bones called vertebrae These are arranged into 5 regions Top 24 vertebrae are held together by ligaments and can move slightly They are separated by discs of cartilage Spine

19. Discs of Cartilage • Have a hard outer layer with a soft jelly like centre • They act as shock absorbers and protect the vertebrae

20. A Slipped Disc • Sometimes soft centre bulges out and compresses spinal nerves

21. People are taller in the morning as their discs are fully expanded • During the day discs become compressed due to gravity and people are shorter in the evening

22. Vertebra Shape • Vertebra have different shapes depending on where they are • General structure

23. Rib Cage • Consists of Sternum, Breastbone and 12 pairs of ribs

24. Ribs 1-7 are connected to the breastbone and are called true ribs • Ribs 8 – 10 are attached to each other at the front of the chest by cartilage they are called False ribs • Ribs 11 -12 are only attached to the spine they are called floating ribs

25. Consists of limbs (arms + legs), the pectoral (shoulder) girdle, and the pelvic (hip) girdle The Appendicular Skeleton

26. Pectoral girdle • Consists of the collar bone (clavicle) and shoulder blade (scapula) • Forms a connection with the vertebral column and the arms (ie. The humerus, radius, ulna, carpals, metacarpals and digits which contain the phalanges)

27. 2 halves joined at the front by cartilage Each half has 3 fused bones Pelvic girdle fused to spine at sacrum Hip bones attach to sacrum at pelvis Hip bones, Sacrum + legs make pelvic girdle Pelvic Girdle

28. Consists of femur, patella, fibula, tibia, tarsals, metatarsals, digits which contain philanges Legs

29. Arms and legs have similar design patterns Each limb ends in 5 digits for this reason they are known as Pentadactyl limbs Limbs

30. Phalanges • The bones in fingers and toes • Each finger and toe has three phalanges • Exceptions are the thumb and big toe which only have two • Important feature of Great apes and humans is that we have opposable thumbs which gives great powers of manipulation

31. "Well, there it goes again ... and here we just sit without opposable thumbs."

32. Enclosed by a membrane called periosteum This membrane contains blood vessels and nerves Long shaft of bone is called the diaphysis The head of the bone is the epiphysis Structure of long bone

33. Cartilage • Cartilage contains a firm, flexible protein called collagen • Collagen fibres are embedded in a matrix of calcium and phosphorous salts • There are no blood vessels and nerves here • For transport cartilage depends on materials diffusing through to the cells that form it • For this reason cartilage is slower to heal than bone

34. Cartilage is found in the pinna of the ear, the nose, trachea, and in between vertebra • It also covers the end of bones to protect bones and reduce friction

35. 3 types of bone • Compact bone • Spongy bone • Bone marrow

36. Compact bone • Made of osteoblasts (bone cells) embedded in a matrix of 70% inorganic (non living) materials and 30% collagen • Blood vessels and nerve fibres are found here • Bone cells and collagen are organic (living)

37. Compact bone is found in the diaphysis of the bone and at the ends of a bone

38. Spongy Bone • Like compact bone that contains lots of hollows (like aero chocolate) • Spaces in spongy bone are filled with red bone marrow that makes red blood cells • Mainly found in epiphysis

39. Bone marrow • Soft fatty substance found in medullary cavity and in spongy bone • Full and active red marrow in young people • Active marrow confined to spongy bone in adults • Medullary cavity of adults contains inactive, yellow fat rich marrow • This can convert to red marrow if needed

40. Bone Growth By the seventh week of embryonic life the skeleton begins to turn from cartilage to bone. This is called ossification

41. Bone Growth Cartilage at joint At birth, all cartilage has been converted to bone except at the joints and internally at the end of the epiphysis along the epiphysis plate. Epiphysis Spongy bone Epiphysis plate Compact/hard bone Diaphysis Marrow Periostium Epiphysis plate Epiphysis Cartilage

42. Bone Growth During growth, osteoblasts at the edge of the growth plate convert the cartilage to bone and new cartilage is formed by mitosis within the growth plate. The growth plate is pushed further into the epiphysis as the bone lengthens. Growth continues until the growth plate is fully calcified.

43. Bone Growth • There are three periods of rapid growth in human development: • during the final trimester of pregnancy the foetus doubles in size. • during the first two years after birth and • 3. during puberty. Growth spurt at puberty Mass/kg Growth spurt after birth Growth slows after puberty and stops at age 24 approx. when the epiphysis plate is fully calcified Time/Years Birth Growth Curve in Humans

44. Adult height cannot be increased beyond that which is genetically determined, even by increasing nutrition.

45. Renewal of Bones • Dependant on physical activity, hormones and diet

46. Physical activity • Bones stressed by physical activity become thicker and stronger • Lack of stress on bones causes them to become thin – a problem for astronauts in weightlessness

47. Hormones • Growth hormones + sex hormones increase the size of bones this is clearly seen in puberty • Parathormone removes calcium from bone to raise calcium levels in blood

48. Diet • It is essential to have calcium in the diet

49. Osteoporosis • This is the loss of the protein collagen from bone • Bones become brittle and easily broken

50. Joints • Where two or more bones meet • Name 3 such places in the body • Different types of joints are classified depending on the movement they allow • How much movement do the joints you have named allow?