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Lesson Note
Subject: Biology
Topic: Support in Vertebrates.
Lesson Objectives: By the end of the lesson, the learners should be able to:
- Give two classes of skeleton;
- List types of vertebrae;
- Describe the limb girdle found in the shoulder region of the human body;
- Differentiate between pectoral and pelvic girdle;
- Differentiate between the long bones of the arm and that of the thigh.
SUPPORT IN VERTEBRATES (SKELETON CLASSIFICATION)
CLASSIFICATION OF SKELETON
The skeleton of vertebrate such as fish, frog, lizard, bird and man consist of bones and cartilages. It can be classified into two. AXIAL SKELETON– which consists of the skull, ribs, sternum and the vertebral column and APPENDICULAR SKELETON – which consists of limb girdles (pectoral and pelvic girdles), and the limbs (the fore and hind limbs).
1. AXIAL SKELETON
a. The Skull: The Skull is made up of flat bones joined together by suture joint which has three parts: Cranium (brain-box), facial skeleton and the jaws; including maxilla (upper) and mandible. Functions
- It protects the brain.
- Also protects the olfactory organ, eyes, middle and inner ear.
- Gives shape to the head. Bears the teeth.
b. The vertebral column: It forms the back bone, protecting the spinal cord. It is made up of 5 groups of bones called the vertebrate each of which is built on similar basic pattern. The vertebrate are held together with strong ligament and comprehensible cartilage pads called into intervertebratal disc.
A TYPICAL VERTEBRA
A typical vertebra has the following structural features
Neural canal: for the passage of the spinal cord.
Neural spine: which projects upward and backward for the attachment of muscle.
Transverse processes: for the attachment of muscles and ligaments.
Centrum: solid bony pieces below the neural canal
Zygapophyses: are the particular surfaces for joining together of successive vertebrate.
This could be pre-zygapophysis (facing inward and upwards) or post-zygapophysis (facing outward and downwards.
TYPES OF VERTEBRAE
i. CERVICAL VERTEBRAE
The first cervical vertebra is called the atlas while the second is called the axis.
The Atlas has a large neural canal, flat and broad transverse processes, short neural spine which could be absent at times. It also has a vertebrarterial canal for the passage of blood vessels. Centrum is absent.
Function of Atlas: It Permits the nodding of the head.
The Axis
It has a broad and flat Centrum, a large and flat neural spine, reduce transverse processes and a vertebra arterial canal. It articulates with the atlas through odontoid process.
Functions
- It permits the turning or twisting of the head.
- Forms pivot joint with the atlas.
ii. THORACIC VERTEBRA
Have a long and prominent neural spine, a pair of short transverse processes, a large neural canal and neural arc and large cylindrical centrums .They also have particular surfaces for attachment of the ribs.
FunctionAids attachment of ribsAssist in breathingAttachment of muscles at the shoulder and back
iii. LUMBAR VERTEBRAE
Each has large and flat transverse processes, broad and flat neural spine, large and thick centrums and well developed zygapophyses. It has extra paired projections namely
anapophysis and metapophysis
Functions of LumbarIt provides attachment for abdominal musclesIt bears considerable weight of the body.
iv. SACRAL VERTEBRAE
This fuse together to form a singular bony mass called sacrum. Each sacral vertebrate has a narrow neural canal, reduced neural spine and large centrums. The first differs from the remaining four by:
- Having a pair of transverse processes which is large and wing-like while the others are attached to the muscles of the back.
- Presence of a small neural canal which generally becomes narrower in the lower four vertebrae.
FUNCTION
- Joins the pelvic girdle to provide support,rigidity and strength.
These are joined together to form a singular bony mass called coccyx. Each has no neural spine, no neural canal and no transverse process. It appears as a solid rectangular mass of bone
Functions
Supports the tail.
Provides attachment for tail muscle.
2. THE APPENDICULAR SKELETON
i. Pectoral girdle: found around the shoulder in man and it consists of two halves which are held by muscles. Each halve is made up of three bones namely;
- Scapula
- Clavicle
- Coracoids
The scapula and coracoids are fixed together as the scapula is flat and triangular with a hollow called GLENOID CAVITY at its tip. This cavity articulates or joins with the head of humerus to form the shoulder joint. The clavicle is a small rod of bone attached to a ligament joining the sternum to the scapula
Functions
The pectoral girdle gives attachment to muscles and ligaments.
It provides firm support to the fore limbs.
ii. Pelvic girdle: This is found around the waist in man and it consists of two halves which are joined to each other ventrally and to the sacrum dorsally. Each halve of the pelvic girdle is made up of three bones. They are:
- Illium
- Ischium
- Pubis
LIMBS
The limbs include the fore (upper) and the hind (lower) limbs. In most vertebrates, both limbs have the same basic plan i.e. each limb has a long bone followed by a pair of two long bones next to this is a set of small bones terminating with five digits.
a. The fore limbs- This is made up of an upper arm bone called humerus which joins with two other long bones at its lower end (radius and ulna) to form the elbow joints. Radius and ulna (the ulna is longer) are the bones of the fore arm, next are the wrist bones called carpals which are a small bones. These are followed by the digit bones called metacarpals which terminate in the phalanges (finger bones). In man, each digit has three phalanges except the thumb which has two phalanges.
b. The hind limbs-This is made up of thigh bones called femur (which is the largest and longest bone in the body). Its round upper end is the end that terminates at two rounded projections called condyles which forms the knee joint together with tibia. A small flat bone called patella is found in front of the knee joint. Next to the femur are tibia and fibula. Tibia is longer and larger. These are followed by bones of the ankle called tarsals. The lower limb terminates at the digit bone metatarsals and each digit is made up of three phalanges.
The ribs
These are long semi circular rods which connects the thoracic vertebrates to the sternum. They are found in the chest region of the body. In man, they are 12 pairs.
FunctionThey form a cage protecting the lungs and the heartThey assist in breathing.
A TYPICAL RIB
A typical rib has a head, a neck and a body. The first seven ribs are connected directly to the sternum through coastal cartilages. They are therefore called true ribs. The next five are called false ribs. The eighth to tenth ribs have a common articulation to the sternum, each one attached to the coastal cartilage to the one above. The eleventh and twelfth pairs of ribs are called floating ribs because they have no connection to the sternum.
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Take a quick test for this lesson.
1. Give two classes of skeleton.
2. List types of vertebrae.
3. Describe the limb girdle found in the shoulder region of the human body.
4. Differentiate between pectoral and pelvic girdle.
5. Differentiate between the long bones of the arm and that of the thigh.
6. Describe the bone connecting the thoracic vertebra to the sternum.
7. Classify the twelve types of ribs.
8. List the structural features of a typical vertebrate.
9. Using the location, structural features and functions, differentiate between atlas and axis.
Questions answered correctly? Bravo!!
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