Skeletal System - Class XI

The vertebral column in adult man comprises of 26 bones- 

There are 7 cervical vertebrae. All cervical vertebrae have apertures in their transverse processes, known as Foramina transversalis, which form vertebro-arterial-canals on either side for vertebral artery to pass through to supply brain and spinal cord.

The hip bone or innominate bone or coxal bone is a large, flattened, irregularly shaped bone. It consists of three parts, the ilium, ischium, and pubis, which are fused in the adult. 

In the given table options i and iv are correctly matched.

So, the correct option is 'A-(ii), B-(iii), C-(iv), D-(i)'.

The pelvic girdle is located in the lower part of the trunk. It consists of three bones that are upper ileum, lower ischium and inner pubis, they fuse to form a stout hip bone. Ventral wall of the pubis has a small bone which is known as cotyloid. The acetabulum is formed by ilium, ischium and pubis, but in mammals, pubis is replaced by cotyloid bone.

The joints between the carpal bones are 'gliding joints'.

Our body is made up of many joints. Each of these joints is of different categories and perform specific functions. They may be movable joints or immovable joints. Among the movable joints, some are hinge joints. This means that they are able to move about one axis. They are a type of synovial joint.

Osteology is the study of the structure and function of the skeleton and bony structures.

• A joint is a location at which two or more bones make contact.
  
• Fibrous or immovable joints are connected by dense connective tissue, consisting mainly of collagen.
  
• Gomposes is a type of fibrous joint. It is a joint between the root of a tooth and the sockets in the maxilla or mandible.
  
• So, the correct answer is 'Gomposes →→ Intercarpal joints'
  

• Gout is a metabolic disease in which crystals of uric acid gets deposited in joints, tendons and surrounding soft tissues.
• Symptoms of gout increase irritation, inflammation of joints and tendon tissue, joints become hot red and swollen.
• Hence accumulation of uric acid crystals in joints causes their inflammation.
• So, the correct answer is 'Accumulation of uric acid crystals in joints causes their inflammation'.

• Joints are points of contact between bones, or between bones and cartilages.
  
• Synovial joints are characterized by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements. Gliding joint is a type of synovial joint.
• Gliding joints allow the bones to glide past one another in any direction along the plane of the joint -up and down, left and right, and diagonally.
• The joint between carpals is gliding joint.
• So, the correct answer is 'Gliding joint  → Between carpals'.

There are six types of synovial joints. These are a pivot, hinge, saddle, plane, condyloid, and ball and socket joints. The pivot joint is a type of synovial joint that allows rotation. The joint between atlas and axis is pivot joint which allows the movement of the head back and forth. The hinge joint is a type of synovial joint which allows movement only in one axis, that is flexion and extension. Knee joint, ankle joint are examples of the hinge joint. Ball and socket joint allows rotation in multiple directions. In this type of joint, ball-shaped surface of one joint lies in the socket-like depression of another joint. The hip joint is an example of ball and socket joint. Saddle joint is the joint present between the carpal and metacarpal of thumb. It allows flexion, extension, adduction, abduction and circumduction movements. It provides stability and flexibility to bones.

Cockroach belongs to Arthropoda which is covered by an exoskeleton. The body is divided into three regions head, thorax and abdomen. They have a true coelom and have open spaces known as sinus. The segmentation is internal as well as internal while in hydra, tapeworm and leech only external segments are present 

There are eight bones that make up the cranium. These are : frontal bone (1), parietal bone (2), temporal bone (2), occipital bone (1), sphenoid bone (1) and ethmoid bone (1).

The human skull is a bony structure that supports the face and creates a cavity for the brain and protects it. The skull is made up of 8 cranial bones, 14 facial bones and 6 middle ears and 1 hyoid bones. So, the total number of bones in the skull are 29 bones.

The hypopharynx is an appendage or thickened fold on the floor of the mouth of many insects, that resembles a tongue. Thus, option B is correct.
The labium is a fused mouth part, which forms the floor of the mouth of an insect. Thus, option C is wrong.
The labrum is a structure corresponding to a lip, especially the upper border of the mouth parts of a crustacean or insect. Thus, option D is wrong.
The maxilla is the jaw or jawbone, specifically the upper jaw in most vertebrates. In humans, it also forms part of the nose and eye socket. Thus, option A is wrong.

The box enclosing and protecting the brain is called as the cranium. The cranium is the part of the skull, that encloses the brain. It is sometimes called as the braincase.

The lower jaw of mammals consists of only one bone, the dentary whereas jaws of other vertebrates are composed of more than one bone. This bone joins the skull at the squamosal bone. This anterior bone of the lower jaw bears the teeth. Hence option A is correct.

The sella turcica forms a bony seat for the pituitary gland. The sella turcica is a saddle-shaped depression in the body of the sphenoid bone of the human skull.

The atlas ($C _1$) is the most superior (first) cervical vertebra of the spine. The atlas's chief peculiarity is that it has no body. It is ring like and consists of an anterior and a posterior arch and two lateral masses. The coccyx commonly referred to as the tailbone is the final segment of the vertebral column in humans and apes. It comprises of three to five separate or fused coccygeal vertebrae below the sacrum. As, both atlas and coccyx are the two first and last bones respectively of the vertebral column they do not have corresponding bones.

Of the 206 bones in the human body, 22 bones are in the skull. The skull consists of 8 cranial bones and 14 facial bones. The hyoid bone (lingual bone) is a horseshoe-shaped bone situated in the anterior midline of the neck between the chin and the thyroid cartilage. The middle ear contains three tiny bones known as the ossicles: malleus, incus, and stapes.

Skull is the part of bony endoskeleton, which protects the brain. Skull is made up of two parts- cranial and facial. In humans, skull consists of 29 bones. Rabbit skull is made up of 53 bones.

There are 7 cervical vertebrae, $C _1$ - $C _7$.  First cervical vertebrae, i.e., atlas and second cervical vertebrae, i.e., axis, and seventh vertebrae are modified; third through sixth are typical; all contain transverse foramina. Atlas supports head, permits "yes" motion of head at joint between skull and atlas; axis permits "no" motion, i.e., rotation movement at joint between axis and atlas.

• Flat bones are made up of a layer of spongy bone between two thin layers of compact bone. They have a flat shape, not rounded
  
• The flat bones are the occipital, parietal, frontal, nasal, lacrimal, vomer, hip bone (coxal bone), sternum, ribs, and scapulae.
  
• Hence ribs are flat bones.
• So, the correct answer is'Ribs'.

Flat bones, such as the cranium, ribs, and sternum, are specifically structured to provide protection for underlying soft tissues and organs.

The patella, also known as the kneecap, is a thick, circular-triangular bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint.
So, the correct option is C. ( Patella )

The stapes is the third bone of the three ossicles in the middle ear. The stapes is a stirrup-shaped bone, and the smallest in the human body. It rests on the oval window, to which it is connected by an annular ligament. Thus, option D is correct.

A bone left in dilute HCl for about three days will become soft and elastic.

Answer is option A i.e. "Bone elongation"
Epiphyseal disk is also called as growth plate. Epiphyseal plate (growth plate), is the region between the diaphysis and epiphysis. Epiphyseal plate/ disk is responsible for the lengthwise growth of long bones. Long bones continue to lengthen, potentially until adolescence, through the addition of bone tissue at the epiphyseal plate

Irregular bones have complex shape and hence, cannot be classified as long, short or flat. Their shape is due to the function they carry out it the body. They provide mechanical support to the body but also protect the spinal cord. Therefore, (b) is the correct answer. 

Short bones are approximately cube shaped i.e length, diameter, width and depth all are same. Examples of short bones are carpal and tarsal bones. Therefore, (c) is the correct answer. 

The first seven pair are attached directly to the sternum 8th, 9th and I0th pairs are attached indirectly to the sternum, and the last two pairs of ribs are called floating ribs because their anterior ends are not attached to either the sternum or the cartilage of another ribs.

First cervical vertebra is called atlas. Second cervical vertebra is known as axis. The atlas supports the head. Axis has a peg like process called Odontoid  process / Dens.

Endosteum is a thin single layer of epithelium, lines the marrow or medullarycavity.

Sella turcica or Turkish saddle' is a depression in the Hoar of the mammalian skull in the sphenoid (Basi sphenoid) bone in which the pituitary body is lodged.

The four coccygeal vertebrae fuse together in adult to form a single small triangular bone called coccyx. It articulates with the tip of the sacrum.

Ends of long bones are covered with cartilage` Ends of long bones takes Part in forming the joint so the ends are covered by hyaline cartilage (articular cartilage).

Tympanic bone is a hollow, flask shaped bone. Its main swollen part called tympanic bulla.

Sella turcica or the Turkish saddle' is a depression in the floor of the mammalian skull in the sphenoid (Basi sphenoid) bone in which the pituitary body is lodged.

Within the matrix of the compact bone of the shaft of long mammalian bones. (like humerus, femur, tibia), a network of branching canals (called haversian canals) is present in which lie the blood vessels.

Synsacrum is a composite bone in birds which consists of about 16 fused vertebrae of different regions.

Humerus is differentiated into three parts head, shaft and lower end. Shaft has a V-shaped deltoid ridge, at its middle.

• Long bones are hard, dense bones that provide strength, structure, and mobility. For example, The thigh bone (femur) is a long bone.
  
• Articular cartilage is hyaline cartilage that is found on the articular surfaces of bone i.e where bones meet and form joints.
  
• Hence  Extremities of long bones possess Hyaline cartilage(articular cartilage).
• So, the correct answer is 'Hyaline cartilage'.

• Long bones are hard, dense bones that provide strength, structure, and mobility, typically found in the upper and lower extremities (arms and legs). For example, the femur (thigh bone) is a good example of a long bone.
  
• Haemopoiesis(production of blood cells) takes place in epiphyses of long bones.
  
• As long bones are hard and dense they provide support and they function as the synthesis of erythrocyte and leucocyte due to the presence of red bone marrow.
  
• So, the correct answer is 'Support, erythrocyte, and leucocyte synthesis',.
  

Human skeleton is divided into two types based on the planes the bones are present. They are Axial skeleton present in the central plane and Appendicular skeleton i.e., bones present in appendages. The appendicular skeleton of 126 bones and the axial skeleton of 80 bones together form the complete skeleton of 206 bones in the human body. So, the given statement is true.

• The central cavity of long bone shafts where red bone marrow and/or yellow bone marrow(adipose tissue) is stored is called the medullary cavity.
  
• Hence yellow bone marrow occurs in the medullary cavity of long bones.
  
• The amount of yellow bone marrow increases with age.
• So, the correct answer is 'Long bones'.

• The coccyx, commonly referred to as the tailbone, is the final segment of the vertebral column in all apes, and analogous structures in certain other mammals.
•  Depending on an individual's development, the coccyx may consist of three to five different bones connected by fused or semi-fused joints and/or disc-like ligaments.
•  The individual bones also fuse together to form a single coccyx throughout adulthood. Hence, Human skeleton altogether contains 206 bones. Some bones are fused in adults, an example of fused bones would be  Coccyx.
So, the correct answer is 'Coccyx'.

Stapes is the third bone of ear ossicles in the middle ear. It is the smallest bone measuring 3*2.5mm roughly. 

There are flat bones in the skull, the thoracic cage, and the pelvis. The function of flat bones is to protect internal organs such as the brain, heart, and pelvic organs.

The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the tibia and kneecap forming the knee joint. By most measures, the femur is the strongest bone in the body. The femur is also the longest bone in the human body.

Ends of long bones are covered with a layer of connective tissue called hyaline cartilage. So, the correct answer is (c).

Haversian Canals are the features of the compact long bones of mammals. These are centrally located and supply nerves and blood vessels to the osteocytes of bones. The Epiphysis of rabbit and diaphysis of frog do not show the Haversian Canals.

Following statements are incorrect regarding a normal human: 

The body of the bird is adapted for flight. One of the key adaptions for this is the fusing of bones into single ossification.The compound structure present in the birds vertebral column is called the synsacrum and is formed by the fusion of 14 to 16 vertebrae. The last part of the synsacrum is formed by the fusion of the caudal vertebrae

The femur, or thigh bone, is the longest,
heaviest and strongest bone in the entire human body and helps support all the body's weight. The weight lifter will therefore have the strongest leg bones.

A bone which is embedded in the tendon is known as sesamoid bone. Patella is a the largest sesamoid bone which articulates with the femur (thigh bone) and covers and protects the anterior articular surface of the knee joint. 

At the ends of each long bone are present epiphyses which are covered with hyaline cartilage. The longitudinal growth of long bones is due to the endochondral ossification of the epiphyseal plate and is stimulated by the production of the growth hormone.
Therefore, the correct answer is option A.

The foramen is the hole is an opening or groove in the bone that allows blood vessels and nerve to enter the bone. It i1s one of the several ovals or circular openings in the base of the skull.

The axial skeleton is the part of the skeleton that consists of the bones of the head and trunk of a vertebrate.

In mammals, like rabbit and humans thoracic vertebrae, ribs and sternum together form the rib cage. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral girdle (shoulder girdle), forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum (with xiphoid process), costal cartilages, and the 12 thoracic vertebrae. 

The vertebro-arterial canal (foramen transversarium) is a characteristic feature of cervical vertebrae, allowing the passage of the vertebral artery.

The scapula is commonly referred to as the shoulder blade. It connects the humerus bone of the arm to the collarbone. It is located between the second and seventh ribs. 

Vertebral column is part of the axial skeleton. It is the flexible column extending from neck to tail.

The sacrum is a part of the vertebral column. It is formed by the fusion of 5 bones. It is a large, triangular bone at the base of the spine. The main function of the sacrum is to connect the spine to the hip bones (iliac). The sacrum is a very strong bone that supports the weight of the upper body as it is spread across the pelvis and into the legs. Thus, the correct answer is option A.

The upward movement of ribs due to contraction of intercostal muscles which in turn increases the anteroposterior diameter of the chest is called as pump handle movement. The outward and upward movement of ribs to increase the transverse diameter of the thorax is termed as bucket handle movement.  Upper ribs show more pump handle activity as they have a transverse axis of motion between costovertebral and costotransverse articulation which makes options A and B incorrect. 

At the spinal column, the rib starts with the rib head (caput costae or capitulum). The rib bone progresses backwards via the rib neck (collum costae) to the rib tubercle (tuberculum costae). This is where the rib body (corpus costae) begins, which curves round to the front with the rib angle (angulus costae).

In human beings, the cervical vertebrae comprise of the vertebrae of the neck, immediately below the skull. This is the smallest of the true vertebrae, and the distinguishing feature is the presence of a foramen or hole in each transverse process and through which the vertebral artery passes.

• The cervical spine is made up of 7 vertebrae. The first 2, C1 and C2, are highly specialized and are given unique names: atlas and axis, respectively. C3-C7 are more classic vertebrae, having a body, pedicles, laminae, spinous processes, and facet joints.
• The typical cervical vertebrae are $C3, C4, C5, and C6$. The atypical cervical vertebrae are C1 – Atlas, C2 – Axis, and C7 – vertebra. The key difference between typical and atypical vertebrae is that typical vertebrae consist of all basic components of a vertebra while atypical vertebrae are the vertebrae that have modified structure due to their position and function.
  
• Hence 3, 4, 5, 6 are typical cervical vertebrae.
• So,the correct answer is '3,4,5,6'.

• Urostyle is a long bone formed from fused vertebrae at the base of the vertebral column in some lower vertebrates, especially frogs and toads.
• In frog Eighth vertebra is amphicoelous and the 9th vertebra is biconvex and is attached to urostyle on the posterior side.
• Hence the Last vertebra of the frog is Urosyyle.
• So, the correct answer is 'Urostyle'.

• Bone is the rigid part that constitutes the vertebral skeleton. It is a connective tissue largely composed of organic protein collagen and the inorganic mineral hydroxyapatite.
• Mineral hydroxyapatite is chemically Calcium phosphate.
  
• Hence the major constituent of vertebrate bone is calcium phosphate.
• So, the correct answer is 'Calcium phosphate'.

• Osteoporosis is a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, bones become weak and may break from a fall or, in serious cases, from sneezing or minor bumps. Osteoporosis means “porous bone.”
  
• Osteoporosis can be caused due to deficiency of vitamin D, while osteomalacia is caused by a deficiency in calcium and phosphorus. 
• Hence Osteoporosis is characterized by deterioration of the bone due to deficiency of phosphorous is an incorrect statement.
• So, the correct answer is 'III alone is incorrect'.

• The spinous process extends posteriorly, or rearward, from the laminae of the vertebra, and is a point of attachment for several muscles, ligaments, and fasciae. 
  
• In cervical vertebrae C2 through C6, there exists a common variation of bifurcation. A spinous process is considered bifurcated when a small 'split' occurs at the distal end.
• ​The bifurcation allows for the nuchal ligament to fall centrally which allows the cervical musculature to attach jointly to this strong ligament, as well as the spinous process without interference at the bony insertion.
  
• Hence the Bifurcated spinous process is present in second and Sixth cervical vertebrae.
• So, the correct answer is 'Second and Sixth cervical vertebrae'.

The opisthocoelous vertebra is concave at the posterior end but not the anterior end. Mostly fish and salamanders are of the opisthocoelous type.

Sternum or breastbone is a flat, narrow and long bone which forms the base for attachment of ribs and is made up of one bone; there are 24 bones or 12 pairs consisting of the rib cage; pelvis consists of 3 bones and face is composed of facial bones which are 14 in number.

Thus, the correct answer is option A.