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.
ii. Hinge joint joint - In this type of joint -surface of one bone articulates with concave surface of another. It is found between the carpals.
iii. Saddle joint - Each bone in a saddle joint resembles a saddle, with concave and convex portions that fit together. It is found between the carpal and metacarpal of thumb.
iv. Pivot joint. - This joint consist of the rounded end of one bone fitting into a ring formed by the other bone. It is found between atlas and axis.
v. Gliding joint - It is formed between bones that meet at flat or nearly flat articular surfaces In this type of joint the It is found between the carpals
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.
Answer the following briefly :
(a) How does a muscle shorten during its contraction and lengthen during its relaxation?
(b) What biological functions are served by the skeletal system ?
(c) Why a red muscle fibre can work for a prolonged period while a white musule fibre suffers from fatigue after a shorter work ?
(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.
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.