CLASS: SS 2

SUBJECT: BIOLOGY                          PERIODS 2:

DURATION:                                       45 MINUTES

TOPIC:                      JOINTS

SUBTOPIC 1:             JOINTS

SUBTOPIC 2:             FUNCTION OF THE SKELETON

SUBTOPIC 3:             SUPPORTING TISSUES IN PLANTS

PREVIOUS KNOWLEDGE: STUDENTS AND FAMILIAR WITH THE

TOPIC

 

OBJECTIVES:    At The End Of The Period(s), students should be able to:

 

Period 1:   

  1. State the type of joint movable and immovable with examples of each type.
  2. Describe the mechanism of joint movement

 

Period 2:   

  1. List the functions of skeleton and supporting tissue in animals and plants.
  2. Describe how these functions are performed.

 

Period 3:

  1. State the different supporting tissues in plants
  2. Describe the arrangement of the supporting tissues present in plants.

References

Essential biology for senior secondary schools 1-3 by Mc Micahel Pg 91-100

Modern Biology for senior secondary schools 1-3 page 269 – 283

 

CONTENT

A joint is a region where two or more bones meet or articulate. The joints and muscles aid body movement. Joints are held together by ligaments (made of stiff, partially elastic fibres) which join bones to bones. There are two main types of joints namely.

  1. Immovable or fixed joints – the joints are firmly fixed by ligaments such that movement of these bones are impossible. Examples include the skull and pelvic girdle. The immovable joints of the skull are called sutures
  2. Movable joints – are joints where two or more bones meet in such a way that the bones move over each other making movement possible. There are 4 main types of movable joints namely:
  3. Ball and socket joint: this type of joint allows movement in all dimensions (3600) it can be found in the shoulder joint (the humerus head fits who the gleniods cavity of the scapula) and the hip joint (the femur head fits into the acetabulum of the pelvic girdle)

alt text

  1. Ball and socket joints

 

  1. Pivot joint allows nodding or rotation of one part of the body on another. It is found between the atlas and axis vertebrae. The odontoid process of the axis acts as a pivot which allows the rotation of the head on the vertebral column.

iii.      Hinge joint allows movement in one direction only (1800) Examples can be found in the elbow (between the humerus and ulna/radius) and knee joints (femur and tibia/fibula)

  1. Gliding or sliding joints – allow the sliding of bones over one another e.g. joints at the wrist and ankle which allow movement of the hand and foot up and down or rotated slightly.

 

The main parts of a joint include

  1. Ligaments are tough, partly elastic bands of tissue which hold two or more bones together at a joint.
  2. Tendons – are extension of connective tissue which surround the muscles. Tendons are non elastic, tough, whitish fibrous materials and connect muscles to bones.
  3. Arboular cartilage are found at the surface of bones at joints where they protect the bones from wear and tear during movement by cushioning the bones.
  4. Synovial membrane: This secretes the synovial fluid which lubricates the joints thus reducing shock and friction between the bones. Capsule  is the space which contains the synovial fluid.

 

MECHANISM OF JOINT MOVEMENT

 

Muscles are bundles of long, thin cells enclosed in sheats of connective tissue. Muscles are attached to bones at two points, the origin where the muscles attach to an immovable bone(e.g. shoulder blade) and the insertion  where the muscles attach to a movable bone, e.g. the radius) Muscles attach to bones by means of tendons. Muscles can only contact and relax but cant lengthen or expand. When muscles contract, it becomes shorter and thicker, thus exerting a expanding force ont eh bone in which it is attached. When muscles relax, it lengthens and becomes thinner. Most muscles act in pairs (antagonistic pairs) so that when one member is contracting, another is relaxing. One member is called the extensor and it extends or straightens a limb by its contraction, the other member is called the flexible  it bends or flexes the limb.

 

The muscles of the upper arm on the humerus are called triceps and biceps. The bicep muscles are attached to the scapular by means of 2 tendons and are found at the front of the humerus. The tricep muscles are found at the back of the humerus and both act or antagonistic manner on impulse received from the central nervous system. Tehbiceps (flexor) contracts by becoming shorter and thicker and at the same time,t the triceps (extensor) relax which bring about the pull of the radius and bendign of the arm. The triceps contract, bicepts relax, which brings about a pull on the ulna and straightening of the arm. Muscular energy for this muscular movement comes from the oxidation of glycogen stored in the muscles (tissue respiration)

 

FUNCTION OF THE SKELETON IN MAN.

  1. Support – body shape is maintained and the rigid framework of the skeleton gives support to the body.
  2. Protection: Serves as protection to the delicate body organs e.g. the skull which protects the brain, the vertebral column which protects the spinal cord, the rib cage, which protects the heart, lungs and blood vessels etc.
  3. Blood cell manufacture: The white and red blood cells are produced in the marrow of long bones.
  4. Mineral salts storage – the skeleton helps to store mineral salts like calcium and phosphorus
  5. Muscles attachment – the skeleton provides places for muscles attachment.
  6. Movement
  7. Respiration: The skeleton (Thoracic bone of the rib cage) with the muscle attached to them assist in respiration.

 

SUPPORTING TISSUES IN PLANTS.

Supporting tissues in plants give plants shape, strength, rigidity and resistance against external forces (wind and water). The major supporting tissues in plants namely:

  1. Collechyma tissues: the Collenchyma cells are living, elongated and unevenly thickened (deposition of extra cellulose) at the corners. The cells are flexible thus allowing bending and twisting strains to which the stem, roots and leaves are subjected to. Collenchymas cells are found in the cortex of stems, roots and in the hypodermis just beneath the epidermis. It provides strength and support (mechanical strength) to young growing plant parts (stems, petioles, leaf blades) below the epidermis in stems and the midrib of leaves and give flexibility and resilience to plants (which enable plants to bend without breaking).

alt text

Collenchyma

  1. Sclerenchyma tissues: Sclerenchyma cells have thickened walls containing lignin, (mec strength) cellulose and other substances and they are found mainly in the pericycle in vascular tissues and cortices of roots and stems. There are

 

There are two types of sclerenchyma, fibres (elongated cells with tapering ends) and slereids(not too elongated). They provide flexibility (fibres) to plants and prevent them from breaking up easily and provide strength, rigidity, hardness and support to plants.

alt text

Sclerenchyma                                           

alt text

parenchyma

 

  1. Parenchyma tissues – are composed of cells with large vacuoles and relatively thin wall. They are living cells with cellulose and many air spaces. It is the most common and abundant plant tissue and can be found in the cortex of stem, phloem, root, leaf, mesophyll, storage tissue and xylem. It can store food and water, function in food synthesis in the leaf mesophyll and give firmness and turgidity to herbaceous plants when the vacuoles are filled with sap.

 

  1. Wood and xylem tissues- are found mainly in vascular tissues of stems, roots and leaves. The xylem tissue is made up of many cells namely:
  2. Tracheids – Non living elongaged tapering cells with thickened, lignified walls which have pits that aid water and dissolved mineral salts passage.
  3. Fibres – are narrow, elongated cells with very thick walls and tapering end walls. It is similar to sclerenchyma.

iii.      Vessels – are long tabular structures formed by fusion of several elongated cells stacked one on top of another.

  1. Xylem parenchyma – are cells with large vacuoles like parenchyma tissues.

Xylem tissues provide strength, support and shape to the plant and conduct water and dissolved mineral salts from the roots to the leaves.

 

  1. Phloem tissues – are located within the vascular bundles in the roots, stems and leaves. The phloem tissues are made up of four cells namely:
  2. Companion cells – are small and short cells which are vertically elongated. Companion cells assist in conduction of food.
  3. Sieve tubes – are elongated rows of cylindrical cells that are arranged vertically. They are living cells and they conduct mainly food.

iii.      Phloem fibres – special cells which strengthen the organs in which they are found.

  1. Phloem parenchyma – similar to parenchyma cells. Provide strength support and also help in food storage.

 

Phloem tissues conduct manufactured food from the area of production to areas where needed and also assist in provision of support to the plant.

FUNCTIONS OF SUPPORTING TISSUES IN PLANTS

  1. Collenchyma, sclerenchyma and wood fibres provide required materials to strengthen the plants against external force.
  2. Protection – Cambium (Constantly dividing cells found between phloem and xylem) and phloem vessels protect the delicate parts.
  3. Conduction: Xylem and phloem conduct water and food respectively
  4. resilience and flexibility
  5. strengthening – sclerenchyma and collenchymas provide strength
  6. District shape

 

INSTRUCTIONAL MATERIALS

Teaching methods procedures

Step 1: Teacher introduce the new topic after revising the previous topic to the students

Step II: Teacher defines joint, states the type sand explains the major parts of a joint

Step III: teacher explains the mechanisms involved in joint movement and explains the functions of skeleton in man.

Step IV: Teacher explains the types, structures and functions of supporting tissues in plants.

Step V: Teacher allows students to ask questions and writes notes under content on the board.

CLASSROOM (ACTIVITIES)

PERIOD 1: Students explain what they understand as joint in man and state the types citing location of each type of joint

Period 2: Students discuss how joint bring about movement and the functions of skeleton

Period 3: Students discuss the types, structures and functions of supporting  tissues in plants.

Evaluation

Period 1:

  1. What is a skeleton?
  2. Describe three skeletal materials found in anmals

Period 2:

  1. What are the types of joints?
  2. Give at least an example of each type of joint

 

Period 3:    State the differences between ligaments and tendon

SUMMARY/CONCLUSION: Teacher summarizes the topic, makes the students notes and makes corrections where necessary.

ASSIGNMENTS

PERIOD 1: WHAT IS A JOINT?

  1. Describe the structure of a joint

Period 2:    With the aid of labeled diagram, describe how muscles act on bones to cause movement of the forelimbs.

PERIOD 3: List and describe the functions of supporting tissue in plants.