Tag: our skeletal system and the skin

The condensation reaction is the type of polymerization reaction in which many monomers join together through bonds forming macromolecules of polymers by giving out byproducts majorly water. The example includes polypeptide chains of proteins or the formation of cellulose.

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.