Welcome to Zoology World

balindrakumar033@gmail.com   25/11/2017,Saturday

WELCOME TO ZOOLOGY WORLD

The science or study of animal life. Together with botany, the study of plant life, it forms the science of biology. Zoology is such a vast subject that most zoologists specialize or focus on the study of particular organisms or taxonomic groups. tion of animals.

Skeletal tissue

SIt provide support and surface for attachment of muscles.Skeletal connective tissue
is mesodermal in origin and forms the frame work of body .

It provide support and surface for attachment of muscles.Skeletal connective tissue is mesodermal in origin and forms the frame work of body .It provide rigidity to body. These protect the various organ and help in locomotion.It is of three types: Cartilage,Bones, Notochord.


Cartilage:

 Cartilage is a solid but semi-rigid and flexible connective tissue.Cartilage is a nonvascular
connective tissue,consisting of cells embeded in a resilent matrix of chondrin..

Cartilage is a solid but semi-rigid and flexible connective tissue.Cartilage is a nonvascular connective tissue,consisting of cells embeded in a resilent matrix of chondrin.Chondrin is a protein of cartilage.Regeneration of cartilage can occur from its peri-chondrium.Cartilage is said to be metabolically nearly inactive.In kids the cartilage cells show 2 types of growth.

(i)Appositional or Perichondral or Secondary or Exogenous growth:

It is due to deposition of matrix and division of chondrogenic cells of periphery.It leads to growth in thickness.

(ii)Endogenous orInterstitial growth:

It is due to deposition of matrix and division in inner cells of cartilage. It leads to growth in size.

Types of Cartilage:


Hyaline cartilage,Fibro cartilage(White firbous cartilage),Elastic cartilage(Yellow elastic cartilage)

1.Hyaline cartilage:

It is most primitive and glass like cartilage.Its matrix is transparent homogenous and pearly white or bluish green in colour,contain chondrin.It is slightly elastic and also known as articular cartilage because it forms the articular surface of joints.Hyaline cartilage is found in trachea larynax and bronchi,limb bone(called hyaline cap),sternum in the hyoid apparatus nasal septum, ribs(sternal parts) larynx(cricoid,thyroid),nasal cartilage(nasal septum).

2.Fibro cartilage(White firbous cartilage):

In this cartilage,the small amount of matrix of cartilage is packed with large number of bundles of thick white(collagen) fibres.So it is toughest and less flexible.It is found in intervertebral discs and acts as shock absorber.It is also found in pubic symphysis and helps in parturition(child birth).The intervertebral discs remain contracted when the body is active,but relaxed when the body is at rest.That is why ,our body becomes a bit taller during sleep and after death.

3.Elastic cartilage(Yellow elastic cartilage):

In this cartilage,the matrix is packed with yellow or elastic fibres which run in all directions to form a network.Owing to the presence of yellow fibres,it is very flexible.It gives recoiling power to structures.It is found in mammalian pinna,pharyngotympanic tube,epiglottis,some laryngeal and bronchiolar cartilages.

What is Bone

Bone is a highly calcified(mineralized),hard and rigid connective tissue.It is the major component of adult vertebrate endoskeleton.Besides its mechanical function of supporting the body architecture and internal organs as a frame work,of protecting delicate organ like brain,heart etc of forming to muscles to faciliate movement and locomotion,the bone is also a metabolically dynamic tissue which functions as a homeostatic reservoir of ions ofcalcium ,magnesium,phosphorous,etc. About 97% of total calcium of body occurs in the endoskeleton.

Structure of bone


Periosteum:

It is a membrane that forms an envelop around the bone .Periosteum comprises of two distinct layers.Outer layer consist of thin white fibrous connective tissue.Inner layer consist of osteoblast.Osteoblasts are spider like bone cells,also known as bone forming cells,because they produces new born materials.

Matrix:

Matrix is composed of protein called ossein.The matrix forms thin plates called lamellae. Lamellae are of three types.Haversian lamellae(ooccur around Haversian canal) concentric or circumferential lamellae(inner to periosteum and outer to endosteum) and interstitial lamellae(between Haversian system).Between the adjacent lamellae are numerous small cavities called lacunae.A lacunae gives off numerous fine branching tubules called canaliculi.Each lucuna is occupied by bone forming cells called osteocyte.

Bone marrow