TISSUE AND SUPPORTING SYSTEM

TISSUE AND SUPPORTING SYSTEM

The skeleton is the hard, bony framework of the body which confers protection, support and shape to organs and soft tissues of the body.

Skeletal Materials in Animals (Forms of Skeleton)

1.     Fluid (hydrostatic) skeleton in earthworm and anemones: fluid pressure is used to provide support.
2.     Bones and cartilages in animals: bone consists of osteocytes (bone cells), protein fibres (collagen) and minerals (mainly calcium phosphate and calcium carbonate). The bone has a hard outer layer (shaft) and a spongy hollow cavity filled with bone marrow. It is found mainly in vertebrates.
3.     Cartilage consists of living cells (chondroblast), carbohydrates and protein fibres. It has a great tensile strength and provides cushioning effect on bones moving against each other. There are three types of cartilage: Hyaline cartilage (found in trachea and bronchi, protruding part of the nose and surface of moveable joints); Fibro-cartilage (found in discs between bones of the vertebral column) and; Elastic cartilage (found in the external ear)
4.      Cuticle (Chitin) in arthropods: chitin is a non-living protein substance with a thin waterproof layer of wax. Organisms with this skeletal material grow by moulting or ecdysis.

Types of Skeleton

1.          Exoskeleton
2.           Endoskeleton
3.          Hydrostatic skeleton

The Mammalian Skeleton

The mammalian skeleton is made up of the axial and appendicular skeleton.

Axial Skeleton

The axial skeleton consists of:

• -          The skull
• -          Vertebral column (backbone)
• -          Ribs

The Skull

The skull is composed of the cranium (brain box) and facial bones.

The cranium consist of several flat bones joined together by saw-like edges called sutures.

The facial bones supports the nose, the eyes and the muscle of the cheeks

Jawbones consist of the upper jaw known as maxilla and the lower jaw known as mandible.

The Vertebral Column

The vertebral column is also known as the backbone or spinal column. The vertebral column is the central supporting structure of the skeleton.

Common Features of the Vertebra

1.         They possess a fairly central hole called neural canal for passage of spinal cord.
2.             They possess a neural spine which projects upwards dorsally for attachment of muscles.
3.        They have two (2) transverse process which projects from the sides for attachment of muscles.
4.        They have centrum which is a solid piece of bone below the neural canal.
5.        They possess facets at the front and back which is a point of contact with another bone.

      Each vertebra is separated from the other by an intervertebral disc.

Bones of the Vertebral Column

	Vertebra type	Man	Rabbit	Rat	Location	Function
1	Cervical	7	7	7	Neck region	Supports the neck
2	Thoracic	12	12-13	13	Thorax (chest)	Articulate with the ribs
3	Lumbar	5	6-7	6	Upper Abdomen	Provide attachment for abdominal muscles
4	Sacral	5	3-4	4	Lower abdomen (Hip)	Form the sacrum
5	Caudal	4	16	27-30	Tail region	Support the tail
	Total	33	44-47	57-60

1.      Cervical Vertebra: they are found in the neck region. Consist of atlas, axis and typical cervical vertebrae.

A.  Atlas Vertebrae: helps with the nodding of the head.

                                         i.   It articulates with the skull

                                       ii.   It has a large neural canal

                                     iii.   It has a flat and broad transverse process

                                     iv.   The neural spine is short/absent

                                       v.   It has no centrum

                                     vi.   It has vertebrarterial canal

B.  Axis Vertebrae: allows twisting of the head.

                                         i.   It has a pin-like transverse process

                                       ii.   It has broad flat centrum

                                     iii.   It has a large and flattened neural spine

                                     iv.   It articulates with atlas through odontoid process

                                       v.   It has vertebrarterial canal

          2.      Thoracic Vertebra

                                         i.   They possess long neural spines

                                       ii.   The transverse process are well-developed

                                     iii.   They have facets for rib articulation

Functions

a). They form thoracic cage with ribs and sternum to protect the heart and lungs

b). They assist in breathing

          3.      Lumbar Vertebrae

                                            i.   They have flattened transverse process

                                          ii.   They have short and flat neural spine

                                        iii.   They have large and thick centrum

Functions

a). They bear the weight of the body

b). They maintain the right and proper gait of the body

        4.      Sacral Vertebrae: they are found in the pelvis. They fuse to form sacrum. They have greatly reduced centrum and they provide support, rigidity and strength.

        5.      Caudal Vertebrae: they are reduced to small centrum bones. They are fused to form coccyx. They have no neural canal, neural spine and transverse process. The function is to stabilize pelvic girdle in man.

The Ribs

There are 12 pairs of rib bones. They articulate dorsally with the transverse process of thoracic vertebrae and ventrally with the sternum. The last pair is unattached ventrally and is known as floating ribs. The ribs protect the heart and the lungs.

Appendicular Skeleton

This consist of 2 pairs of limbs and 2 pairs of limb girdles.

Limbs: the limbs are divided into two

      1)      Forelimbs: these consist of:

a.    Humerus (upper arm)

b.    Radius and ulna (forearm)

c.    Carpal (wrist bones)

d.    Metacarpal (hand bones)

e.    Phalanges (fingers)

      2)      Hind limbs: these consist of:

a.    Femur (thigh)

b.    Tibia and fibula (lower leg)

c.    Tarsal (ankle bone)

d.    Metatarsal (foot bone)

e.    Phalanges (toes)

The limb girdles consist of pectoral and pelvic girdle

     1)      Pectoral girdle: this consist of scapula (shoulder blade), clavicle (collar bone) and coracoid. The scapular is a flat bone with two processes- coracoid and acromion, with a deep notch called glenoid cavity.

      2)      The pelvic girdle consists of the ilium (hip bone), ischium and pubis.

JOINTS

A joint is a place where two or more bones meet. Bones are joined together by ligaments. The articulating surface of bones at movable joints is covered by smooth articular cartilage.

Types of Joints

1.         Ball and socket joint: found in the shoulder and hip joint
2.         Hinge joint: found in the elbow and knee joints
3.         Pivot joint: found between the axis and atlas
4.         Gliding or sliding joint: found at the wrist and ankle

Mechanism of Joint Movement

Muscles are attached to bones by tendons and they control movement at joints. Muscles work by contraction and relaxation. Two muscles are needed to move a joint and their action is antagonistic.

Structure of Joints

A typical joint consist of

1.        Ligament: holds two bones together in a joint
2.        Tendons: connect muscles to bones
3.       Articular cartilage: provide cushioning effect to bones, protecting the articular surfaces of the bone from wear and tear
4.         Synovial fluid: lubricates the joints
5.         Synovial membrane: secretes the synovial fluid

Functions of the Skeleton

1.         Support
2.         Protection
3.         Locomotion (movement)
4.         Shape
5.         Production of blood cells
6.         Assisting in breathing
7.         Storage of mineral salts

Supporting Tissues in Plants

A herbaceous stem is kept erect by a combination of turgor of its living cells, inelastic cuticle and supporting tissues.

Types of Supporting Tissues in Plants

1. Parenchyma tissue: these may be spherical or elongated cells with large vacuoles filled with cell sap. Parenchyma tissues are found at the cortex of stem, phloem, root, leaf, storage tissues and xylem. Parenchyma tissue supports herbaceous plants by turgor, storage of starch and conducts water and gases across the plant.
2. Sclerenchyma tissue: is mostly dead cells with cell walls filled with cellulose or lignin. Sclerenchyma tissue could be:
• Fibres: are elongated cells with tapering ends
• Sclereids: are not so elongated cells
• Sclerenchyma helps in providing rigidity, strengthens and supports the plants
3. Collenchyma tissue: The collenchyma gives the plant strength and provides resilience (flexibility) and support for young stems and leaves, and mechanical support to the plant
4. Xylem tissue/wood: strengthens the plant and conducts water and solutes.

Differences between the functions of the vascular tissues of plants and mammalian skeleton

SKELETON	VASCULAR TISSUES
-aids breathing	does not aid breathing;
-does not conduct water/food	conducts water/food;
-aids movement/locomotion in mammals	does not aid movement/locomotion;
-protects some vital/delicate parts/organs;	does not protect vital/delicate parts/organs;
-composed of bones/cartilage	composed of dense protoplasm and lignified walls.