Blood cell production
Within the bones of the skeleton bone marrow produces both red and white blood cells. Red blood cells are usually produced in the ends of long bones such as the humerus and the femur and in some flat bones such as the pelvis and the sternum. While white blood cells are mainly produced in the shafts of the long bones.
The bones of the skeleton also happen to be able to store vital minerals such as calcium and phosphorus which can be distributed to other parts of the body when in demand and are required.
By analysing the skeleton we can find that the human skeletal system has two major structures. This helps to identify and classify bones because they can be found in the structures depending on their location on the body. The two types of structure are:
The axial skeleton is the bones which forms the central axis of the human body. It helps to structure the body and is the main support of the body. The axial skeleton includes the following:
Vertebral column (spine)
The axial skeleton is comprised of the 80 bones in the skull, ribs, and sternum.
The Appendicular Skeleton
The appendicular skeleton has 126 bones from the shoulders, pelvis, and attached limbs. Each bone is comprised of three major sections, the compact bone, the soft bone marrow, and the sponge bone. The soft bone marrow is found within the hollow centre of the bone - this is where red blood cells are produced.
1) Pectoral Girdles (4 bones) - Left and right Clavicle (2) and Scapula (2).
2) Arm and Forearm (6 bones) - Left and right Humerus (2) (Arm), Ulna (2) and Radius (2) (Fore Arm).
3) Hands (54 bones) - Left and right Carpal (16) (wrist), Metacarpal (10), Proximal phalanges (10), Middle phalanges (8), distal phalanges (10).
4) Pelvis (2 bones) - Left and right ilium (2)
5) Thigh and leg (8 bones) - Femur (2) (thigh), Tibia (2), Patella (2) (knee), and Fibula (2) (leg).
6) Feet and ankles (52 bones) - Tarsals (14) (ankle), Metatarsals (10), Proximal phalanges (10), middle phalanges (8), distal phalanges (10).
Types of bones
Flat bones – the main job of a flat bone is to provide protection. A good example of this is the cranium that protects the brain. Other flat bones include the scapula, skull, pelvis, sternum and ribs
Long – the main job of a long bone is to provide movement. A good example of this is the Humerus which allows movement in the arm. Other long bone examples are the femur and phalanges.
Irregular – these types of bones are bones that do not fall into any of the other categories because of their peculiar form. Irregular bones serve various purposes in the body, such as protection of nervous tissue (such as the vertebra protects the spinal cord) and being multiple anchor points for skeletal muscle attachment (as with the sacrum). Other irregular bone examples are the vertebrae, facial bones, ear bones.
Short – Short bones are mainly there for the bones that are as wide as they are long (cube shaped). Their main job is to provide support and stability with little to no movement. Examples would be the carpals/tarsals
Sesamoid – Sesamoids are found in locations where a tendon passes over a joint, such as the hand, knee, and foot. Functionally, they act to protect the tendon and to increase its mechanical effect. An example of a sesamoid bone is the patella (knee cap, sits inside a tendon, changes the angle of pull for quadriceps muscle).
The musculoskeletal system
In this assignment I am going to identify the location of the major muscles in the human body, describe, explain and then attempt to analyse the function of the muscular system and the different fibre types.
Location of major muscles
(See diagram attached for location of the major muscles)
Types of muscle
There are 3 main types of muscles in the body, these are:
Cardiac or heart muscle - Cardiac muscle tissue forms the wall of the heart and the muscle fibres do not get fatigued, which is needed as the heart is continually pumping blood around the body, so you would not want the muscle to fatigue. Cardiac muscle's contraction is usually not under conscious control, this means that it is involuntary which is useful as you would not want to have to keep remembering to tell your heart to pump.
Smooth muscles (internal organs) - Smooth muscle tissue is in places like blood vessels, the stomach, intestines, and urinary bladder. Smooth muscle fibres are usually involuntary which means they aren't under conscious control and they are smooth to allow easy passage of food through the digestive system. Certain smooth muscle fibres like the ones in the uterus however, keep their shape and size.
Skeletal muscles (striped or voluntary muscles) - Skeletal muscles are attached to bones and it is striated. Skeletal muscle tissue can be made to contract or relax by conscious control so this means it is voluntary.
The skeletal muscles are around 40-45% of a person’s total body weight. They are called skeletal because they are attached to the bones of the skeleton and are also called voluntary muscles because a person’s body can control their movement and actions. Each muscle is can contract and relax to make the body move. There are around 600 muscles in a human body and each are organized into categorise to what action they perform, these are;
Extensors - these open a joint and flexors close a joint.
Adductors - these draw part of the body inwards
Abductors - move the body outwards
Levators raise a part of the body depressors lower part of it.
Each muscle is made up of a group of muscle fibres. A small muscle can be made up of a few bundles but larger muscles are made up of hundreds of bundles. Movement of these muscles are under voluntary control of the brain which means that our body can control them. This happens through chemical and electrical impulses that are sent to the brain through nerve endings. Skeletal muscles are used when the body isn't moving because the muscles of posture are used for when the body is sat down or standing to prevent it from falling over or becoming limp. The muscles that cause us to breathe are always working even when the body is asleep. Speaking, writing, texting all use communication of the skeletal muscles.
Functions of the muscular system
- How muscles produce movement
- Cross Joints – Muscles have to cross over joints to make the movement possible, the bones are like levers with the joints being a pivot point for the muscles to cross over to then generate the movement.
- Contract - Muscle fibre generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same. Voluntary muscle contraction is controlled by the central nervous system. The brain sends signals through the nervous system to the motor neuron that innervates several muscle fibres. Involuntary muscles such as the heart or smooth muscles in the gut and vascular system contract as a result of non-conscious brain activity.
- Muscle Tone is where the muscles are always semi-contracted to be able to sit and stand as they have to hold the body in that upright position.
- Muscles work together in groups
- Agonist – This is the prime mover and the muscle that is contracting to create the movement. So during a bicep curl for example, the agonist muscle would be the bicep as it is the prime mover.
- Antagonist – This is the opposite muscle to the prime mover. This has to relax to allow the movement to happen. So during a bicep curl for example, the antagonist muscle would be the tricep as it is the muscle which relaxes to allow the movement to happen.
- Synergist – These are the muscles that assist the agonist to create the movement. So during a bicep curl for example, the synergist muscle would be the brachioradialis and brachialis as this assists the bicep to create the movement of the bicep curl.
- Fixator – These muscles hold other joints in place so that only the desired movement takes place. So during a bicep curl for example, the fixator muscle would be the deltoid as this holds the surrounding joints in place to stop any unwanted movement during the bicep curl.
- Types of Contraction
- Isometric – This type of contraction is where they are actively working, but there is no movement taking place and the muscle length also doesn’t change. Also, the blood pressure increases because the blood flow is at a low.
- Concentric – This type of contraction is where the muscle is getting shorter, which then causes the joint to move in the desired action. An example is bending the elbow from straight to fully flexed, causing a concentric contraction of the biceps brachii muscle.
- Eccentric – This type of contraction is where the muscle lengthens, making the muscle return back to its original length after shortening against resistance. For example, when kicking a football, the quadriceps muscle contracts concentrically to straighten the knee and the hamstrings contract eccentrically to decelerate the motion of the lower limb.
- Isokinetic – This type of contraction is when the muscle contracts and gets shorter at a constant speed. Examples of using this contraction in day to day and sporting activities are rare. The best example is breast stroke in swimming, where the water provides a constant and even resistant to the movement of adduction.2
There are three types of muscle fibres and they are:
* Type 1- Slow Oxidative/Slow Twitch
* Type 2a - Fast Oxidative Glycolytic/Fast Twitch
* Type 2b - Fast Glycolytic/Fast Twitch Type B
Fast and Slow twitches
In terms of people who participate in athletics:
Type 1 are red fibres and is often called slow oxidative/slow twitch or fatigue resistant fibres. They contain large amounts of myoglobin and the type 1 generates ATP (Adenosine Triphosphate) by the aerobic system (oxidative). It is split ATP at a slow rate and has slow contraction velocity. Type one has many mitochondria (where aerobic energy is produced in cells) and many blood capillaries (lots of 02). Type 1 is also resistant to fatigue, found in large numbers in postural muscles. Finally type 1 is needed for aerobic activities like long distance runners.
Type 2a is also a red fibre and is also called a fast twitch A or fatigue resistant fibres. Type 2a contains large amounts of myoglobin and many blood capillaries. It has a high capacity for generating ATP by oxidation. It splits ATP at a very fast rate and this is why there is a high contraction velocity. Type 2a is resistant to fatigue but not as much as slow oxidative fibres (type 1). Type 2a is needed for sports such as middle distance 400-800metres or swimming.
Type 2b is a white fibre and is also called fast twitch B or fatigable fibres. Type 2b contains low myoglobin content and few mitochondria. It also has few blood capillaries. Type 2b has large amounts of glycogen and splits ATP very quickly. It fatigues easily meaning it is only needed for sports like sprinting with short sharp bursts of energy.
There are similarities and differences between these 3 types of fibres. Type 1 and type 2a are similar because they are both fatigue resistant, contain many blood capillaries and have a large amount of myoglobin but they are different in that type 1 is a slow twitch and type 2 a is a fast twitch. Both type 1 and type 2a are red fibres and type 2b is a white fibre. Type 1 and type 2a are released slowly and last longer whereas type 2b is for sprinters who release quickly over a short distance.