Chapter 40: The human
musculoskeletal system
Leaving Certificate Biology
Higher Level
Function of the Skeleton
• Functions:
1.Shape and support
2.Protection: of internal organs
3.Movement: muscles use skeleton as levers
4.Production of red and white blood cells
5.Hearing: ossicles vibrate and amplify vibrations
6.Ingestion and digestion: physical digestion in the
mouth
7.Storage: of minerals (calcium and phosphorus) that can
be taken by the body when needed
Structure
SCAPULA
of the
HUMERUS
Human VERTEBRAE
Skeleton
PELVIS
CRANIUM
MANDIBLE
CLAVICLE
RIBS
RADIUS
ULNA
FEMUR
PATELLA
FIBULA
TIBIA
Axial Skeleton
• 80 bones:
–
–
–
–
–
Skull
Ossicles
Spine
Ribs
Sternum
Appendicular
Skeleton
• 126 bones:
– Pectoral girdle
– Pelvic girdle
– Limbs
Axial
skeleton
(blue)
Appendicular
skeleton
(pink)
Axial Skeleton
• 80 bones: skull, ossicles, vertebrae, ribs,
sternum
• Skull: cranium (8 fused bones) and facial
bones
• Vertebral column: 33 small bones appears as only 26 due to fusion of the
vertebrae of the sacrum (5 fused
vertebrae) and coccyx (4 fused vertebrae)
Axial Skeleton - continued
• Ossicles: hammer (malleus); anvil (incus);
stirrup (stapes)
• Ribs: 12 pairs originate from the vertebral
column; 7 pairs are “true ribs” (attached
directly to sternum); 3 pairs are “false ribs”
(attached indirectly to the sternum by only
cartilage); and 2 pairs are “floating ribs”
(attached to spine only)
Ossicles: Hammer, Anvil, Stirrup
Rib Cage
• 7 pairs of
true ribs
• 3 pairs of
false ribs
• 2 pairs of
floating ribs
Vertebral
Column
C1 - 7
T1 - 12
L1 - 5
S1 - 5
Co1 - 4
Vertebrae and Vertebral Discs
• Vertebrae: protect spine and give support to
thoracic cavity and abdomen
• Invertebral discs:
– Located between each vertebra – held in place
by ligaments
– Elastic and compressible
– Provide flexibility and act as shock absorbers
– Can “slip” – where soft centre of disc bulges out.
It is called prolapsed invertebral disc. Can push
against nerve often causing severe pain.
Structure of Vertebrae
Appendicular Skeleton
• 126 bones involving:
– Pelvic girdle (hips)
– Pectoral girdle (shoulders):
• Scapula
• Clavicle (collar bone)
– Limbs:
• Arms: humerus, radius, ulna, carpals, metacarpals,
and phalanges
• Legs: femur, tibia, fibula, tarsals, metatarsals, and
phalanges
Anatomy of
the Human
Hand
I-V. Metacarpal bones
1 and 4. Distal phalanx
2. Middle phalanx
3,5. Proximal phalanx
6. Sesamoid bones
7. Distal interphalangeal joint
8. Proximal interphalangeal joint
9. Metacarpophalangeal joint
10. Carpometacarpal joints
11. Trapezium
12. Trapezoid
13. Capitate
14. Hamate
15. Scaphoid
16. Lunate
17. Triquetrum
18. Pisiform
19. Radius
20. Ulna
A-E: Toes 1-5. (A:Great toe)
I-V. Metatarsals
1,3: Distal phalax
4: Middle phalax
2,5: Proximal phalax
6. Interphalangeal joints
7. Metatarsophalangeal joints
8. Sesamoids
9. Head of metatarsal
10. Shaft (body) of metatarsal
11. Base of metatarsal
12. Cuneiforms (medial; intermediate;
and lateral)
13. Navicular
14. Cuboid
15. Talus
16. Calcaneus
17. Tibia
18. Fibula
19. Tarsometatarsal joints
20. Transverse midtarsal joint
Macroscopic Anatomy of a
Long Bone
• Bone is mixture of organic (35%) and
inorganic (65%) material
Periosteum
• Thin layer of connective tissue that covers
the outer surface of bone in all places
except at joints (which are protected by
articular cartilage)
Compact bone
• Dense and forms the surface of bones
(80% of the weight of human skeleton)
• Hard with very few gaps
• Function: support and protection
Medullary cavity
• Central cavity of the bone shaft where
yellow marrow (adipose tissue) is stored
• Located in the main shaft of the bone
(diaphysis)
• In children this area is also involved in the
formation of red blood cells, so red marrow
is present
• Function: storage of fat and formation of
RBCs in children
Spongy bone
• Found at the expanded heads of long bones
• Low density and low strength but very high surface
area
• Fills the inner cavity of long bones
• In some bones the spaces are filled with red bone
marrow where the production of blood cells occurs
• Contains most of the arteries and veins
• Functions: production of RBCs and delivery of
oxygen and nutrients
Cartilage
• Type of dense connective tissue
• Composed of collagenous fibers and/or elastic
fibers which are embedded in a firm gel-like
ground substance called the matrix
• Cartilage is avascular (contains no blood
vessels) and nutrients can only diffuse through
the matrix
• Cartilage is found in many places in the body
including the joints, the rib cage, the ear, the
nose, the bronchial tubes and between
intervertebral discs
• Functions: provides framework upon which
bone deposition can begin and supplies smooth
surfaces for the movement of articulating bones
Compact
bone
Joints
• Immovable – fused joints of the skull
• Slightly movable – vertebral joints
• Free-moving/Synovial:
– ball-and-socket joints of the shoulder and hip
– hinge joints such as the elbow and knee
Ligaments and Tendons
• Ligaments are strong, slightly elastic
bands of fibrous tissue (collagen) – they
control the range of movement of a joint
• Tendons are extremely strong, inelastic
bands/cords of collagen – they attach
muscles to bone
Skeletal Muscle
• Contractile tissue – has ability to shorten
and generate a pulling force
• Voluntary muscles – we can consciously
control contractions of skeletal muscle
• Function: movement and temperature
regulation in the body as they generate a
lot of heat during movement
Antagonistic Muscle Pairs
• Antagonistic muscle are pairs of muscles
where the action of each pulls the
attached bone in the opposite direction to
the other
• Most of the body’s 700 muscles operate
as part of antagonistic muscle pairs
– e.g. biceps and triceps of the upper arm
– e.g. hamstrings and quadriceps of the upper
leg
Musculoskeletal Disorder
Osteoporosis
• Brittle-bone disease - bones are porous/less dense
• Often results in compression fractures in the vertebrae and in
the neck of the femur (broken hip)
• Possible cause: - Bone replacement has slowed down
- Menopause in women
• Prevention:
- Physical exercise during puberty reduces
- risk of developing the disease in old age
- Calcium-rich diet and drinking fluoridated
- water maintains bone density
• Treatment:
- Females use HRT (but bone material
- already lost is not replaced!
- Physical exercise, dietary calcium, and
- vitamin D are recommended
Musculoskeletal Disorder
Rheumatoid Arthritis
• Joint (fingers, wrists, ankle most common) become stiff and
sore (inflammation occurs)
• Articular cartilage has been destroyed and bones fuse
• Possible cause: - Immune reaction against the body’s own
- cartilage
• Prevention:
- No known preventative measure
- yet
• Treatment:
- Pain-killers and anti-inflammatory drugs
- are administered
- Badly affected areas, such as hip or knee
- can be replaced with artificial joints
Growth and Development in Bones
• Skeleton of early embryo is mostly cartilage
• Bone formation begins just before week 8
• Specialised cells called osteoblasts secrete
a thick layer of bone around the cartilage of
the diaphysis – a tube of bone now encircles
the diaphysis
• Cartilage continues to grow at ends –
epiphyses – bone elongates
• After birth the epiphyses start to calcify
Growth and Development in Bones
• Cartilage remains at the junctions between
the diaphyses and epiphyses – this area is
called the growth plate
• The growth plates enable the bones to
elongate during childhood and puberty and
eventually calcify and are replaced by bone
at the end of puberty when fully grown – 18
in females and 21 in males
Growth and Development in Bones
Bone Renewal
• Bone is a living organ and is capable of selfrenewal
• Bone is constantly broken down and replaced
(parathormone involved)
• Skeleton is completely replaced every 7 years
and complete replacement slows down with age
• Osteoclasts remove calcium and osteoblasts
lay calcium down
• Renewal of bones is affected by the hormone
parathormone but also by exercise levels and
dietary calcium