Skeletal System

• Skeletal system consists of framework of bones and cartilages • Aids in body movement, gives shape

• Bones have hard matrix due to calcium • cartilage is pliable matrix due to chondrium salts • 206 bones and few cartilages • Skeleton divided into two div. Axial and Appendicular skeleton

• Axial skeleton comprises 80 bones distributed along main axis of the body • The Skull, Vertebral column, Sternum and Ribs constitute axial skeleton • The skull is composed of two sets of bones- cranial and fascial • A single U-shaped bone – hyoid present at the base of buccal cavity

• Middle ear contains three tiny bones – Malleus, Incus, Stapes = Ear Ossicles

SKELETAL SYSTEM Axial Skull 28 – Cranium 8, Facial 14, Ear Oscicle 6 Vertibral Column 27 – Hyiod bone 1,Vertibrae (in Adult) 26 Tharax 25- Sternum 1, ribs 24

Appendicular Skeleton Upper region Pectoral girdle 4, arm and hands 60 Lower Region – Pelvic girdle 2, Legs and feets 60 Total Bones - 206

Cranial Bones

6

SKELETAL SYSTEM  Joint are essential for all types of movements involving the

bony parts of the body

• Fibrous joints do not allow any movement. This type of joint is shown by the flat skull bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures, to form the cranium. • In cartilaginous joints, the bones involved are joined together with the help of cartilages. The joint between the adjacent vertebrae in the vertebral column is of this pattern and it permits limited movements.

• Vertebral column is formed by 26 vertebrae • Extends from the base of the skull • Each vertebra has a central hollow portion through which spinal cord passes. • Vertebral column: Cervical, Thoracic, Lumbar, Sacral, Coccygeal

• Cervical vertebra are seven

The Skeletal System •

Parts of the skeletal system include: – – – –

•

Bones (skeleton) Joints Cartilages Ligaments

Divided into two divisions: 1. Axial skeleton (skull, ribs and vertebra) 2. Appendicular skeleton (pelvis, extremities)

Functions of Bones • • • • •

Support of the body Protection of soft organs Movement due to attached skeletal muscles Storage of minerals and fats Blood cell formation

The Axial Skeleton • Forms the longitudinal part of the body • Divided into three parts – Skull – Vertebral column – Bony thorax

The Axial Skeleton

Figure 5.6

The Vertebral Column • Vertebrae separated by intervertebral discs • The spine has a normal curvature • Each vertebrae is given a name according to its location Figure 5.14

The Bony Thorax • Forms a cage to protect major organs

Figure 5.19a

The Bony Thorax • Made-up of three parts – Sternum – Ribs – Thoracic vertebrae

Figure 5.19a

The Appendicular Skeleton • Limbs (appendages) • Pectoral girdle • Pelvic girdle

The Pectoral (Shoulder) Girdle • Composed of two bones – Clavicle – collarbone – Scapula – shoulder blade

• These bones allow the upper limb to have exceptionally free movement

Bones of the Shoulder Girdle

Figure 5.20a–b

Bones of the Shoulder Girdle

Figure 5.20c–d

Bones of the Upper Limb • The arm is formed by a single bone – Humerus

Figure 5.21a–b

Bones of the Upper Limb • The forearm has two bones – Ulna – Radius

Figure 5.21c

Bones of the Upper Limb • The hand – Carpals – wrist – Metacarpals – palm – Phalanges – fingers

Figure 5.22

Structural Classification of Joints • Fibrous joints – Generally immovable

• Cartilaginous joints – Immovable or slightly moveable

• Synovial joints – Freely moveable

Fibrous Joints • Bones united by fibrous tissue • Examples – Sutures – Syndesmoses • Allows more movement than sutures • Example: distal end of tibia and fibula Figure 5.27a–b

Cartilaginous Joints • Bones connected by cartilage • Examples – Pubic symphysis – Intervertebral joints

Figure 5.27d–e

Synovial Joints • Articulating bones are separated by a joint cavity • Synovial fluid is found in the joint cavity

Figure 5.24f–h

Features of Synovial Joints • Articular cartilage (hyaline cartilage) covers the ends of bones • Joint surfaces are enclosed by a fibrous articular capsule • Have a joint cavity filled with synovial fluid • Ligaments reinforce the joint

Structures Associated with the Synovial Joint • Bursae – flattened fibrous sacs – Lined with synovial membranes – Filled with synovial fluid – Not actually part of the joint

• Tendon sheath – Elongated bursa that wraps around a tendon

The Synovial Joint

Figure 5.28

Types of Synovial Joints Based on Shape

Figure 5.29a–c

Inflammatory Conditions Associated with Joints • Bursitis – inflammation of a bursa usually caused by a blow or friction • Tendonitis – inflammation of tendon sheaths • Arthritis – inflammatory or degenerative diseases of joints – Over 100 different types – The most widespread crippling disease in the United States

Clinical Forms of Arthritis • Osteoarthritis – Most common chronic arthritis – Probably related to normal aging processes

• Rheumatoid arthritis – An autoimmune disease – the immune system attacks the joints – Symptoms begin with bilateral inflammation of certain joints – Often leads to deformities

Clinical Forms of Arthritis • Gouty Arthritis – Inflammation of joints is caused by a deposition of urate crystals from the blood – Can usually be controlled with diet

Developmental Aspects of the Skeletal System • At birth, the skull bones are incomplete • Bones are joined by fibrous membranes – fontanelles • Fontanelles are completely replaced with bone within two years after birth

• Sternum is a flat bone on the ventral side of thorax • 12 pairs of ribs, each one is connected to vertebral column and sternum

• 8, 9, 10 pairs of ribs do not articulated directly with sternum but join the 7th rib with help of hyaline cartilage. Are called false ribs • Last 2 pairs (11, 12) are not connected ventrally and are called floating ribs. • Thoracic vertebrae, ribs, sternum together called rib cage.

• The bones of limbs along with girdles constitute appendicular skeleton • Each limb is made of 30 bones • Fore limb bones: humerus, radius, ulna; Then carpals (wrist), Metacarpals (plam), Phalanges (digits)

• Femur (thigh bone) is longest bone; tibia, fibula, tarsals (ankle bones),

• metatarsals and phalanges (digital bones) are bones of legs (hind limb). • A cup shaped patella cover the knee- knee cap

SKELETAL SYSTEM  Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones.  Such an arragement allows considerable movement.  These joints help in locomotion and many other movements. Ball and socket joint (between humerus and pectoral girdle), Hinge joint (knee joint), Pivot joint (between atlas and axis), Gliding joint (between the carpals) and Saddle joint (between carpal and metacarpal of thumb) are some examples.

• Pectoral and Pelvic girdle help in articulation of upper and lower limbs, respectively with axial skeleton • Pectoral girdle consists of a clavicle and scapula • Pelvic girdle consists of two coxal bones. Each coxal bone is formed by fusion of three bone – ilium, ischium and pubis

• Joints: • Joints are points of contact between bones, or between bones and cartilages.

• Joint acts as fulcrum. Force generated by muscle is used to carry out movement thru joints, where the joint acts as a fulcrum • Three types of joints; • Fibrous joints: do not allow any movement, (flat skull bone as cranium • Cartilaginous joints: bone are joined together with the help of cartilages. • Synovial joint is characterized by the presence of fluid filled synovial cavity between articulating surfaces of the two bones

• Ball and socket joint – between humerus and pectoral girdle • Hinge joint (knee joint) • Pivot joint (between atlas and axis) • Gliding joint (between the carpals) • Saddle joint (between carpal and metacarpal of thumb)

DISORDERS OF MUSCULAR AND SKELETAL SYSTEM  Myasthenia gravis: Auto immune disorder affecting neuromuscular

junction leading to fatigue, weakening and paralysis of skeletal muscle.  Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.  Tetany: Rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.  Arthritis: Inflammation of joints.  Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased levels of estrogen is a common cause.  Gout: Inflammation of joints due to accumulation of uric acid crystals.

Write true or false. If false change the statement so that it is true.

(a) Actin is present in thin filament ► True (b) H-zone of striated muscle fibre represents both thick and thin filaments. ► False, H -zone of striated muscle fibre represents thick filament. (c) Human skeleton has 206 bones. ► True (d) There are 11 pairs of ribs in man. ► False, There are 12 pairs of ribs in man. (e) Sternum is present on the ventral side of the body. ► True

Name the type of joint between the following:(a) atlas/axis ► Pivotal joint (b) carpal/metacarpal of thumb ► Saddle joint (c) between phalanges ► Hinge joint

(d) femur/acetabulum ► Ball and Socket joint (e) between cranial bones ► Fibrous

(f) between pubic bones in the pelvic girdle ► Cartilaginous joint

Fill in the blank spaces: (a) All mammals (except a few) have __________ cervical vertebra. ► seven (b) The number of phalanges in each limb of human is __________ ► 14 (c) Thin filament of myofibril contains 2 'F' actins and two other proteins namely __________ and __________. ► troponin, tropomyosin (d) In a muscle fibre Ca++ is stored in __________ ► sarcoplasmic reticulum (e) __________ and __________ pairs of ribs are called floating ribs. ► 11th and 12th (f) The human cranium is made of __________ bones. ► eight