Skeletal System Flashcards
Major types skeletons found in the animal kingdom
Hydrostatic - fluid filled body cavity which is enclosed by the body wall. e.g: gastrovascular cavity of cnidarians, psedocoelom in nematodes and coelom in annelids.
Exoskeleton - rigid outer covering of the body.
Endoskeleton - hard skeleton which is buried in soft tissues of the animal.
Common functions of the skeletal system
Support
Protection
Movement
2 main parts of the human skeleton and its constituents
Axial skeleton - skull, vertebral column, sternum and ribs
Appendicular skeleton - girdles (pectoral and pelvic) and limb bones
Human skull consists of how many bones
21
Sutures
Immovable / ossified joints
Bones in the cranium
Frontal bone
2 parietal bones
Occipital bone
2 temporal bones
Ethmoid bone
Sphenoid bone
Thirteen other bones forming the skeleton of the face.
two zygomatic bones (cheek), the maxilla (upper jaw bone), two nasal bones, two lacrimal bones, the vomer, two palatine bones, two inferior conchae and the mandible (lower jaw bone).
Human cranial capacity
nearly 1.5 L
Which structures permits nodding movements
On the inferior surface of the cranium there is foramen magnum to provide passage to spinal cord. Two smooth rounded knobs (Occipital condyles) on either side of the foramen magnum articulates with the first vertebrae (atlas vertebrae) which permits nodding movements.
fontanelles
In the cranium, soft membranous regions called fontanelles are present which allow slight compressions at birth facilitating parturition. Fontanelles become replaced by bones within 1-2 years of life.
sinuses
Several air filled cavities lined by ciliated mucous membrane are present in the skull (in the sphenoid, ethmoid, maxillary and frontal bones). Sinuses provide resonance to voice and reduce the weight of the skull.
2 processes of lower jaw
Condyloid process which articulates with the temporal bone to form the temporal-mandibular joint; Coronoid process which gives attachment to muscles and the ligaments
Temporal bone contains three processes
zygomatic process (which forms part of the zygomatic arch), mastoid process and styloid process. They provide surfaces for muscle attachments.
Vertebral column
Vertebral column is a strong flexible rod consisting of 26 linearly arranged bones. It consists of 24 separate vertebrae extending downwards from the occipital bone of the skull, the sacrum (formed from 5 fused vertebrae) and coccyx (formed from 4 small fused vertebrae).
No.of cervical, thoracic and lumbar vertebrae
7 cervical
12 thoracic
5 lumbar
Main function of the curvatures of spinal cord
Maintaining erect posture
Provides protection to the spinal cord
Which type of vertebrae is known as the typical vertebrae
Lumbar vertebrae
Special features of cervical vertebrae
transverse processes of a cervical vertebra have a foramen on each side to provide passage for the vertebral artery. The spinous process of these vertebrae is bifid.
Special features of axis vertebrae
It has a small body with a superior projections called odontoid process which articulates with the atlas vertebra above. The head pivots (turns on side to side) on this joint
Thoracic cage consists of
thoracic cage (which is made up of sternum, ribs and thoracic vertebrae)
How many pairs of ribs are found in the thoracic cage
12
Contribution of human axial skeleton to maintain upright posture
Presence of 2 primary curvatures and 2 secondary curvatures
Size of vertebrae becomes larger towards the end of the vertebral column
Sacral vertebrae are fused to form a large triangular shaped sacrum to support the weight
Upper limb consists of
Humerus, radius, ulna, 8 carpel bones, 5 metacarpal bones and 14 phalanges
Lower limb consist of
Femur, tibia, fibula, patella, 7 tarsal bones, 5 metatarsal bones and 14 phalanges
What is the heaviest, strongest and the longest bone in the body
Femur
Osteoporosis
Osteoporosis is a condition associated with the reduction of bone density due to the exceedance of the bone reabsorption rate over the deposition rate. Factors causing osteoporosis include hormonal imbalances (especially at menopause), calcium deficiency and environmental factors.
Osteoarthritis
Osteoarthritis is a degenerative non-inflammatory disease that causes pain and restricted movements in the affected joints. risk factors include excessive use of affected joints, female gender, increasing age, heredity and obesity.
Slipped disc
An injury or weakness can cause the inner portion of the intervertebral disc to protrude through the outer ring. This condition is called ‘slipped disc’.
Main types of joints and their locations
Ball and socket - Shoulder joint (incomplete), Hip joint (complete)
Hinge joint - Elbow joint, knee joint, ankle joint, joints between phalanges
Pivot joint - Odontoid process of the axis with atlas
Lateral and medial
A lateral orientation is a position away from the midline of the body. For instance, the arms are lateral to the chest, and the ears are lateral to the head. A medial orientation is a position toward the midline of the body. An example of medial orientation is the eyes, which are medial to the ears on the head.O
What is the currently accepted model of striated muscle contraction
Sliding filament theory
Muscle contraction
Skeletal muscle contain myofibrils. Striated muscle cells contain repeating units known as sarcomeres. Within these contractile units thick filaments (myosin) and thin filaments (actin) are present.
Currently accepted model of skeletal muscle contraction is the sliding filament theory. According to this theory sarcomeres are found within Z lines to which actin filaments bind while myosin filaments are bound to the M line which is present at the middle of the sarcomere. Myosin filaments contain myosin heads which has binding sites on the actin filament. When an ATP molecule bound to the myosin head at the resting stage is hydrolysed, it causes the myosin head move into a higher energy state which causes the myosin heads to bind to actin filaments forming a cross bridge. Only due to the action of Ca2+ ions binding sites of actin filaments becomes functional. As a result the actin filaments are pulled over the myosin filaments resulting the muscle to contract.
