Biology Chapter 20 Locomotion And Movement

The vertebral column is differentiated
into
i. Cervical (7),
ii. Thoracic (12),
iii. Lumbar (5),
iv. Sacral (1-fused) and
v coccygeal (1-fused) regions starting from the skull.

The bones of the legs are:
i. Femur
ii. Tibia  
iv. Fibula
iv. Tarsals
v. Metatarsals
vi Phalanges

On the basis of location the muscles can be of three types :
i. Skeletal.
ii Visceral and
iii. Cardiac.

Masseter (Jaw muscles).

Joints. 

A motor neuron alongwith the muscle fibres connected to it constitute a motor unit.

The junction between a motor neuron and the sarcolemma of the muscle fibre is called the neuromuscular junction or motor-end plate.

H zone.

Visceral muscles are located in the inner walls of hollow visceral organs of the body like the alimentary canal, reproductive tract, etc.

Osteoporosis is the age-related disorder characterised by decreased bone mass and increased chances of fractures. It is common in females as decreased levels of estrogen is a common cause.

The cardiac muscles are striated in appearance. They are involuntary in nature as the nervous system does not control their activities directly.

The two occipital condyles (dicondylic skull) help in the articulation of the skull region with the superior region of the vrtebral column.

Skeletal system : It forms the main supporting frame work of the body. It consists of the framework of bones and a few cartilage. The system plays a major role in the movement of the body. 

The human skeletal system is made up of 206 bones and a few cartilages. It is divided in to two main categories.

A. Axial skeleton : It is present on median longitudinal axis of body e.g. skull, vertebral column, sternum, ribs etc. It comprises of 80 bones. 
i. The skull - is composed of two sets of bones cranial and facial, that totals to 22 bones. Cranial bones are 8 in number.
ii. The vertebral colummn - is formed by 26 serially arranged units called vertebrae and is dorsally placed. It extends from the base of the skull and constitutes the main framework of the trunk. Each vertebra has a central hollow portion (neural canal) through which the spinal cord passes.
iii. Sternum is a flat bone on the ventral midline of thorax.

iv. Ribs - There are 12 pairs of ribs. Each rib is a thin flat bone connected dorsally to the vertebral column and ventrally to the sternum. The first 7 pairs are called True ribs, the 8th, 9th and 10th are called False ribs, and the 11th and 12th are called Floating ribs. 

B. Appendicular skeleton : It is present on sides and present in appendages and associated with them. It includes the bones of the limbs and the pectoral girdles, pelvic girdles.

i. Bones of the limbs - each limb is formed of 30 bones. The bones of the hand are humerus, radius and ulna, carpals (8), metacarpals (5) and phalanges (14).
The leg is made up of Femur, tibia and fibula, tarsals (7) metatarsals (5) and phalanges (14). A cup shaped bone called patella cover the knee ventrally (knee cap).

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

Skull : It has two sets of bones - the cranial and facial, that totals to 22 bones. Cranial bones are 8 in number. They form the hard protective outer covering, cranium for the brain. The facial region is made up of 14 skeletal elements which form the front part of the skull. A single U-shaped bone called hyoid is present at the base of the buccal cavity and it is also included in the skull.

A. Cranium : It encloses the brain. Cranium has following eight bones :

(a) Frontal bone (one)

(b) Parietal bones (two)

(c) Occipital bone (one)

(d) Temporal bones (two)

(e) Sphenoid bone (one)

(f) Ethmoid bone (one)

B. Bones of face : Face has fourteen bones namely :

(a) Nasals (two)

(b) Maxilla (two)

(c) Palatines (two)

(d) Mandible (one)

(e) Zygomatic bones or cheek bones (two)

(f) Inferior nasal conchae (two)

(g) Vomer (one)

(h) Lacrimal (two)

1. It protects the brain from injuries. 

2. It helps in the movement of lower jaw.

3. It helps in the protection of eyes.

4. It helps in the protection of internal ear.

Function of ribs :

1. It protects the vital organs and blood vessels

2. It expands and contracts along with the lungs to allow for efficient breathing

Ribs : There are twelve pairs of ribs. The ribs are of three types :

1. True ribs : There are seven pairs of true ribs. At one end they are attached to vertebral column and at the second end they are attached to sternum.

2. False ribs : There are three pairs of false ribs. At one end these are attached to vertebral column and at second end these get attached to each other.

3. Floating ribs : There are two pairs of floating ribs. These are attached to vertebral column and the second end is free.

Sternum : It lies in the centre in thoracic region on ventral sides. It is a flat bone on the ventral midline of thorax.

Functions of sternum :

1. It provides the position for the attachment of ribs.

2. It takes part in the formation of rib cage which protects the heart and lungs.

Vertebral column : It is formed by 26 serially arranged units called vertebrae and is dorsally placed. It extends from the base of the skull and constitutes the main framework of the trunk. central hollow portion (neural canal) through which the spinal cord passes. It has a central hollow portion (neural canal) through
which the spinal cord passes.  The vertebral column is differentiated into cervical (7), thoracic (12), lumbar (5), sacral (1-fused) and coccygeal (1-fused) regions starting from the skull.  The number of cervical vertebrae are seven in almost all mammals including human beings. The vertebral column protects the spinal cord, supports the head and serves as the point of attachment for the ribs and musculature of the back. The vertebrae are divided into following categories :

1. Cervical vertebrae : These are present in neck. These are seven in number (All mammals have seven cervical vertebrae).

2. Thoracic vertebrae : These are present in thoracic region. There are twelve thoracic vertebrae.

3. Lumbar vertebrae : These are present in abdominal region and are five in number.

4. Sacral vertebrae : There are five sacral vertebrae present in pelvic region. These get fused to form one sacrum.

5. Coccygeal vertebrae : These are four in number and are present below sacrum. These fuse to form one vertebra.

Functions of vertebral column :

1. It protects the spinal cord.

2. It supports head.

3. It provides erect posture, balance and stability for the body.

4. It provides attachment points for the ribs, pelvic bones, and many muscles.

5. Allows for flexibility and mobility.

6.Supports the structure and weight of the body in various activities.

Pectoral girdle : The pectoral girdle is formed of two halves. Each half consists of a clavicle and a scapula . 

1. Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs. The dorsal, flat, triangular body of scapula has a slightly elevated ridge called the spine which projects as a flat, expanded process called the acromion.  Below the acromion is a depression called the glenoid cavity which articulates with the head of the humerus to form the shoulder joint.

2. Clavicle is collar bone. It is a slender bone with two curvatures. 

Pelvic girdle or Hip girdle : It consists of two coxal bones. Each coxal bone is formed by the fusion of three bones – ilium, ischium and pubis. At the point of fusion of the above bones is a cavity called acetabulum to which the thigh bone articulates. The two halves of the pelvic girdle meet ventrally to form the pubic symphysis containing fibrous cartilage.

 Function of pelvic girdle.

1. It provides space for attachment of bones of hind limbs.

2. It provides movement to hind limbs.

3. The muscles of hind limbs are inserted into pelvic girdles.

4. It provides protection to abdominal viscera.

Bones of forelimb : Each limb is made of 30 bones.
A. Forelimbs -  There are two forelimbs each having thirty bones.
These are :
i. Humerus — (1)
ii. Radius-ulna — (2) 
iii. Carpals — (8)
iv. Metacarpals — (5)
v. Phalanges — (14)

B. Hindlimb : There are two hindlimbs. Each hindlimb has thirty bones.
These are :
i. Femur — (1)
ii. Patella — (1)
iii. Tibia-fibula —(2)
iv. Tarsdals — (7)
v. Metatarsals — (5)
vi. Phalanges — (14)

Dislocation : When a bone is displaced from its specific position, then it is said to be dislocated and the phenomenon is called dislocation of bone.

Fractures : A fracture is a complete or incomplete break in a bone resulting from the application of excessive force

Types of movements :

The cells of our human body display three types of movements, namely amoeboid, ciliary and muscular.
i. Amoeboid movement - Cells like macrophages and leucocytes in the blood exhibit amoeboid movement.  Cytoskeletal elements like microfilaments are also involved in amoeboid movement.
ii. Ciliary movement - is shown by cells of our internal tubular organs which are lined by ciliated epithelium. The coordinated movements of cilia in the trachea help us in removing dust particles and some of the foreign substances inhaled alongwith the atmospheric air. Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.
iii. Muscular movements - is shown by our limbs, jaws, tongue, etc, require muscular movement. The muscular movement is used for locomotion and other movements by human beings and majority of multicellular organisms. 

Muscular fatigue : is the decline in ability of a muscle to generate force. It can be a result of vigorous exercise but abnormal fatigue may be caused by barriers to or interference with the different stages of muscle contraction. It happens when the muscles respire anaerobically and produce lactic acid. The accumulation of lactic acid leads to fatigue. 

(b) Functions of skeletal system :

1. It provides mechanical support.

2. It protects the essential organs as heart, brain, spinal cord etc.

3. It plays role in breathing.

4. It helps in locomotion.

5.  It checks entry of food into glottis at the time of swallowing of food.

(c) Red muscle fibres contain myoglobin which stores oxyen as oxymyoglobin and it also has more number of mitochondria. Due to sufficient supply of oxygen little lactic acid is formed. These muscles contract slowly and remain in the contracted state for a long time. TDue to more energy and less lactic acid these muscles do not fatigue in less time. 

White muscle fibres have no myoglobin. So, lactic acid is formed in them. Moreover, their contraction is fast, thus they get fatigued.

Skeletal muscle is made of a number of muscle bundles or fascicles that our held together by a common collagenous connective tissue layer called fascia.
ii. Each muscle bundle contains a number of muscle fibres.
iii. Each muscle fibre is lined by the plasma membrane known as sarcolemma enclosing the sarcoplasm.
iv. Since the muscle fibre's sarcoplasm contains many nuclei it is caleed as a is a syncitium.
v. The  sarcoplasmic reticulum of the muscle fibres is the store house of calcium ions.
vi. The muscle fibre has a large number of parallelly arranged filaments in the sarcoplasm called myofilaments or myofibrils.
vii. Each myofibril has alternate dark and light bands on it. The striated appearance is due to the distribution pattern of  Actin and Myosin proteins. The light bands contain actin and is called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin. 
viii. In the centre of each ‘I’ band is an elastic fibre called ‘Z’ line . The thin filaments are firmly attached to the ‘Z’ line. The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line.
ix. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. The portion of the myofibril between two successive ‘Z’ lines is considered as the functional unit of contraction and is called a sarcomere. 

A muscle cramp is a sudden and involuntary contraction of one or more muscles. They are usually characterised by pain and swelling.

Hypertrophy : Increase in the size of muscles is called hypertrophy. Increase in the size of muscle may occur due to exercise. Due to repeated and forceful contraction of muscles, mass of muscle increases and so does the number of mitochondria, filaments in sarcomeres and amount of sarcoplasm.

Atrophy : Decrease in the size of muscle is called atrophy. Atrophy is due to immobilization of muscles. Mass of muscles decreases due to decrease in number of mitochondria, filaments in sarcomeres and amount of sarcoplasm. An injury to a nerve which supplies a muscle can also cause atrophy

The striated appearance is due to the distribution pattern of two important proteins – Actin and
Myosin. The light bands contain actin and is called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin proteins.  The proteins are arranged as rod-like structures, parallel to each other and also to the longitudinal axis of the myofibrils. Actin filaments are thinner while the myosin filaments, are thicker. An elastic fibre called ‘Z’ line which bisects the I band. The thin filaments are firmly attached to the ‘Z’ line. The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils. 

Thin or Actin filaments :
The light bands contain actin and is called I-band or Isotropic band, whereas the dark band called ‘A’ or Anisotropic band contains myosin.  Actin filaments are thinner and are called thin filaments. The myosin filaments are called thick filament. The thick filaments in the ‘A’ band are also held together in the middle of this band by a thin fibrous membrane called ‘M’ line. The ‘A’ and ‘I’ bands are arranged alternately throughout the length of the myofibrils.

Each actin filament is made of two ‘F’  or filamentous actins. These are helically wound to each other. The ‘F’ actin is a polymer of monomeric
‘G’ (Globular) actins. Two filaments of another protein, tropomyosin are also present close to the ‘F’ actins throughout its length. Troponin a complex protein is found at regular intervals on the tropomyosin. 

Smooth Muscle Fibres :

Occurrence : They are present in the walls of hollow visceral organs like stomach, intestine, lungs, arteries, veins, urinary bladder etc.

Shape : Spindle shaped with narrow or pointed ends.

Structure : TheThey do not exhibit any striations and are snooth in appearance. The unstriped muscle fibres may occur singly or may occur in groups and form sheets. Each unstriped muscle fibre is bounded by plasmalemma. The sarcoplasm contains an oval nucleus in centre. It also has number of myofibrils but without light and dark bands. These muscle fibres contract slowly and relax slowly that is why they do not get fatigued. 
The muscles are not under the control of the nervous system and hence are called involuntary muscles.
Functions - They muscle assist, for example, in the transportation of food through the digestive tract and gametes through the genital tract.

Cardiac Muscle Fibres :

Occurrence : They are present in myocardium of heart.

Structure : Each cardiac muscle fibre is bounded by plasmalemma. They are separated from each other by intercalated discs. These intercalated discs act as boosters. The adjacent muscle fibres are connected by oblique cross walls. The cardiac muscle fibre has deep in centre a slightly oval nucleus. The myofibrils are present and have light and dark bands. The cardiac muscle fibres have abundant blood supply that is why they are of dark red colour. These fibres contract quickly and take double the time to relax and that is why they never feel fatigued.

Control : They are controlled by central and autonomic nervous system.

 There are 3 main types of muscles.

1. Striated muscle fibres or skeletal muscles.

2. Unstriped or smooth muscle fibres or visceral muscles.

3. Cardiac muscles

Mechanism of muscular contraciton :
The Sliding filament theory explains the movement of the muscles. The theory was given by A.F. Huxley
According to this theory actin and myosin filaments slide past each other with the help of cross bridges to reduce the length of sarcomere and actin filaments which meet in centre of sarcomere.

1. When the stimulus of a motor nerve reaches neuromuscular junction then the vesicles present in the synaptic knobs secrete Acetyl choline which diffuses into sarcomere through membrane channel of muscle fibre.

Na⁺ also flow through channel into sarcomere and results action potential.

2. The muscle fibre which is polarised, after receiving acetyl choline becomes depolarised at that end.

3. The wave of depolarisation spreads due to invagination of sarcolemma called T tubes and Z lines.

4. Due to depolarisation, the sarcoplasmic reticulum secretes Ca⁺² ions which bind to specific site present on troponin component of actin filament. Conformational changes occur in Troponin molecule and active sites of F actin molecules are exposed where the cross bridge of myosin filaments gets joined to actin filaments.
5. The cross-bridges take energy from ATP and get rotated inward. Thus sarcomeres contract as Z-lines come closer.

6. Finally whole muscle contracts and H-lines disappear.

7. ADP molecules take energy from creatine~ phosphate and get converted into ATP.
8. The cross-bridges which have been rotated inward may rotate more after taking more energy from ATP molecule. Thus it brings more contraction of sarcomere.

Fig. Relationship between the actin and myosin myofilaments in the (A) relaxed and (B) contracted states

Osteoporosis :

Definition : It is reduction in bone tissue mass causing weakness of skeletal strength (G. osteon = bone, pros = pore, oisis = condition.)

Factors :

1. Excessive resorption of Ca⁺² from bones : It results from excessive resorption of calcium and phosphorus from the bone, which leads to vertical compression or crush fracture of the vertebrae.

2. Menopause and Ca⁺² absorption : Osteoporosis occurs in postmenopausal women and elderly men. It may result from defective intestinal calcium absorption.

3. Environmental factors : Possible environmental factors include smoking, excessive drinking and decreased exercise. Osteoporosis is more common in women than in men, and in old than middle aged persons.

4. Sex hormones : Imbalances of some hormones, thryocalcitonin, parathormone etc also cause osteoporosis.

5. Vitamin D : Deficiency of vitamin D causes osteoporosis.

The movements and locomotion are neccessary among the animals because of following reasons :

1. Need for searching of shelter, food and water.

2. To escape from predators.

3. For shifting to favourable environment from an unfavourable one.

4. The movemenets of alimentary canal help in movement of food from one part of alimentary canal to next.

5.  The ciliary movements help in the meovement of ova in fallopian tubes.

6. Movements of diaphragm and ribs help in breathing.

7. Movement of vocal cords help in the production of sound.

Role of calcium in muscle contraction When the muscle fibre is depolarized then Sarcoplasmic Reticulum releases calcium ions which bind with specific site present on troponin component of actin filament. Increase in Ca++ level leads to the binding of calcium with a subunit of Troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge. Thus, sarcomere contracts .

Joints are the point of contact between bones or between bones and cartilages.
Role of joints in movement :

Muscle twitch -  Muscle twitching is also called muscle fasciculation. Twitching involves small muscle contractions in the body.
Whereas 
Tetany - Tetany is rapid spasm in the muscle due to low Ca⁺⁺ in body fluid. 

Fig. Human Skull

Fig. Ribs and Rib Cage

 Vertebral Column

Types of movements in cells of human body : The different types of movements exhibited by the cells of human body :

1. Amoeboid movement : Some specialised cells in our body like macrophages and leucocytes in blood exhibit amoeboid movement. ln this type the movement is done by the formation of pseudopodia by the streaming of protoplasm (as in Amoeba). Cytoskeletal elements like microfilamens are also involved in amoeboid movement.

2. Ciliary movement : Ciliary movement occurs in most of our internal tubular organs which are lined by ciliated epithelium. The coordinated movements of cilia in the trachea help in removing dust particles and some of the foreign substances inhaled along with the atmospheric air. Passage of ova through the female reproductive tract is also facilitated by the ciliary movement.

3. Muscular movement : Movement of our limbs, jaws, tongue etc. require muscular movement. The contractile property of muscles are effectively used for locomotion and other movements by human beings and majority of multicellular organisms. Locomotion requires a perfect coordinated activity of muscular, skeletal and neural.

Myosin filament : Each myosin (thick) filament is  a polymerised monomeric proteins. The monomeric units are called Meromyosins. These constitute make one thick filament.

Each meromyosin has two important parts, a globular head with a short arm and a tail, the former being called the heavy meromyosin (HMM) and the latter, the light meromyosin (LMM). The HMM component, i.e.; the head and short arm projects outwards at regular
distance and angle from each other from the surface of a polymerised myosin filament and is known as cross arm. The globular head is an active ATPase enzyme and has binding sites for ATP and active sites for actin.

Thick filament (above) and a myosin molecule (below)

Action filament :

1. Each actin (thin) filament is made of two “F” (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomelic ‘G’ (Globular) actins.

2. Two filaments of another protein, tropomyosin also run close to the ‘F’ actins throughout its length.

3. A complex protein troponin is distributed at regular intervals on the tropomyosin.

Structure of thick and thin filaments

The sliding filament theory explains the mechanism of muscle contraction. A proposed mechanism of muscle contraction in which the actin and myosin filaments of striated muscle slide over each other to shorten the length of the muscle fibres (see sarcomere). Myosin-binding sites on the actin filaments are exposed when calcium ions bind to troponin molecules in these filaments. This allows bridges to form between actin and myosin, which requires ATP as an energy source. Hydrolysis of ATP in the heads of the myosin molecules causes the heads to change shape and bind to the actin filaments. The release of ADP from the myosin heads causes a further change in shape and generates mechanical energy that causes the actin and myosin filaments to slide over one another

The important steps muscle contraction:
1. Muscle contraction is initiated by a signal sent by the central nervous system (CNS) via a motor neuron and reach the neuromuscular junction. As a result, neurotransmitter (Acetyl choline) which generates an action potential in the sarcolemma.
2. This spreads through the muscle fibre and causes the release of calcium ions into the sarcoplasm.

3. Increase in Calcium level leads to the binding of calcium with a subunit of troponin on actin filaments and thereby remove the masking of active sites for myosin. Utilising the energy from ATP hydrolysis, the myosin head now binds to the exposed active sites on actin to form a cross bridge.
4. The actin filaments are pulled. As a result, the H-zone reduces. It is at this stage that the contraction of the muscle occurs.

5. After muscle contraction, the myosin head pulls the actin filament and releases ADP along with inorganic phosphate. ATP molecules bind and detach myosin and the cross bridges are broken and decreases the calcium ions contraction. As a result, masking the actin filaments and leading to muscle relaxation.

B.

tetanus

Tetanus results in sustained muscular spasms. This is due to muscle fatigue.

D.

Columnar epithelium is present in the stomach lining.
Tendon is dense connective tissue and connects muscle to bone.
Tip of nose consists of elastic cartilage. 

C.

the central gap between actin filaments extending through myosin filaments in the A-band

H-zone in skeletal muscle is the central gap between actin filaments extending through myosin filaments in the A -band. Alternate myosin filaments in the A-band. An alternate arrangement of dark and light bands gives the striated appearance to a skeletal muscle. At the centre of A-band, a comparatively less dark zone called H -zone is present. In the centre of H-zone, M -line is present, formed by the threats that connect the myofilaments.

B.

Accumulation of uric acid crystals in joints causes their inflammation.

Inflammation of joints due to the accumulation of uric acid crystals is gout.The fibrous joint is formed by the flat skull bones, which fuse end - to -end with the help of dense fibrous connective tissue in the form of sutures to form cranium. The vertebral column is formed by 26 serially arranged units called vertebral. The less secretion of progesterone cause abortion as it basically supports a pregnancy.

C.

The joint between atlas an axis in the pivot, which is an example of synovial joint characterised by the presence of a fluid -filled the synovial cavity between the articulating surface of the two bones. Knee joint (hinge joint) is a synovial joint characterised by the presence of fluid-filled synovial cavity between the articulating surface of the two Bones. Fluid cartilage between two bones having limited movements is slightly movable joint. In freely movable joints fluid filled between two joints provides a cushion in gliding joint. the articulating bones can slide upon another.

A.

Fibrous joint

Fibrous joints are immovable joints in that occur between the bones of the cranium and in the tooth sockets. They do not allow movement because the bones are held firmly together by bundles of strong white collagen fibres. The immovable joints are often known as the sutures. The periosteum that covers the bones dips between them as a septum

C.

Production of body heat

Production of body heat is the function of muscles. The contraction of muscle produce heat, which keeps the body warm during the winters. 

D.

Gliding joint is a type of synovial joint, found between carpal bones and tarsal bones.
The cartilaginous joint between surfaces of skull bones. The pivot joint is found between the atlas and axis. Hing joint is found in the elbow, knee ankle and interphalangeal joint.

A.

the neuromuscular junction

Stimulation of a muscle fibre by a motor neurone occurs at neuromuscular junction neuron activated a muscle to contract during the excitation-contraction coupling of vertebrate skeletal muscles

B.

Osteoporosis-decrease in bone mass and higher chances of fractures with advancing age

Osteoporosis is age-related disease in which bone loose minerals and fibres from the matrix causing decreased bone mass and higher chances of fractures with advancing age. Major causative factors of osteoporosis are imbalance of hormones like calcitonin of thyroid, parathormone of parathyroids, sex hormones and deficiencies of calcium and vitamins. 

D.

humerus with scapula

Glenoid cavity articulates humerus with scapula. It is a feature on the scapula (shoulder blade or shoulder bone). It is slightly concave from above downwards and from side to side. It is shallow and a site of attachment of glenoid labrum (glenoid ligament), which forms fibrocartilaginous rim around the glenoid cavity. It is important because it has the effect of depending the socket into which head of humerous (bone) rests, forming the shoulder joint). It represents a type of synovial, ball and socket joint. 

C.

thigh are striated and voluntary

Thigh muscles are a skeletal muscle that is striated and voluntary skeletal muscles tissue is closely attached to skeletal bones. 

B.

Clavicle and glenoid cavity are found in a pectoral girdle. Each half of pectoral girdle consists of the clavicle and a scapula. Glenoid cavity is a depression below the acromion (the expanded process of scapula). The glenoid cavity articulates with the head of the humans to form the shoulder joint.

B.

Cartilage is usually described as a vascular, as the blood vessels innervate only the outer fibrous sheath of cartilage, called perichondrium. The cornea is the transparent anterior portion of the outer coat of the vertebrate eye covering the iris and the pupil. It is avascular as it lacks lymphatic and blood vessels.