Structure of the human body


Structure of the human body

Human body is a balanced system. Its activity is subject to well-coordinated work of all systems:

1. Central Nervous System consists of brain and spinal cords, through the nerve roots it manages and controls all processes in a body.
2. Endocrine System carries out the control function, but, unlike the Central Nervous System, the control is performed not by transmitting of signals to the nerves. But through the action of hormones (glands produce chemicals), which are transported through the blood to the organs of influence.
3. Cardiovascular System provides exchange of nutrients between tissues, transports the toxic products to organs (kidneys, skin and lungs), that lead out these substances.
4. Digestive System absorbs nutrients from food.
5. Urinary System removes from the blood toxic substances and provides reproduction.
6. Musculoskeletal System.

The largest system of the body is Musculoskeletal. It creates the shape of our body and defines the external manifestations of life, such as work, entertainment, gestures, etc.

Movement is the basis of our life. It is realizes through coordinated work of muscle, contractions of which are transmitted to the bones, where joints are located.

Unlike other mammals, human body has unique structure, which determines its function: bipedalism (when we move in space, relying on two legs, holding the body in a vertical position and have two upper limb for everyday tasks and balancing while our walk). Structures of the locomotor apparatus in such position bear loads because of gravity forse. These loads increase for several times while carrying cargo.

The vertical position of the body likens man to a spring, which is ready to be leveled and convert potential energy of motion into kinetic energy.

Vertebral Column

Vertebral Column is the base of our body and axis, that allocates the load from head to the pelvis and transmits it to the lower limbs. It performs following functions: supporting, protective (protects spinal cord) and motor.

Vertebral Column consists of separate parts that perform individual functions:
1. Cervical region – mobile region, which consists of seven vertebrae, supports head, turns it to the source of anything or allows us to see something.
2. Thoracic rigion – sedentary region, consists of twelve vertebrae, fixed with ribs, which participates in the creation of the chest cavity.
3. Lumbar rigion – very moviable, built of massive 4-5 vertebrae, that bear main load, keeping body weight.
4. Lumbosacral region – fixed formed vertebrae, which anatomically in the development of the human body fused into a single bone. Forms joints and bones of the pelvis, involved in the redistribution of body weight on lower limbs.
5. Coccygeal region or tailbone – the final region of the spinal column, which is also formed from fused vertebrae. Tailbone is one of the supportive points while sitting and fixing point for pelvic floor muscles.

So spine consists of vertebrae, united in a complexed system – intervertebral motor segment(movable connection located along two vertebrae).

What is the structure and function of the intervertebral motor segment?
Each vertebra can be roughly divided into anterior and posterior sections. Anterior -vertebral body, posterior – bow of spinous, transverse and articular processes. These sections are allocate, even in a structure of the intervertebral motor segment.

Anterior section is formed by articular disc with surrounding parts of the vertebral bodies, front and rear longitudinal ligaments that limit mobility at anterior and rear.
Articular disc has a special structure. It consists of two parts:
– Central – Nucleus Pulposus (Gelatin-like substance that for 88% consists of water and the rest of it are proteins);
– Peripheral – the fibrous ring (connective formation, which is closed in a circle around the nucleus pulposus and limits its displacement to the sides).

Posterior section is strengthed by yellow sacrospinale and illiolumbar ligaments. Movement is provided by zygapophysial (facet) joints. Based on the functions of Nucleus Pulposus, it should be seen as a ball between two planes. It is called articulated joint, it moves in varies dimensions. While loading of Nucleus Pulposus, it expands to sideways and amortizes (reduces) the load on Vertebral Column in general.

How does the Vertebral Column functions in general?
Movements in the intervertebral segment are possible in many dimensions, but their amplitude is very small because they are limited with ligaments and facet joints in the posterior section of the spine. Only through the complex of movements, many spinal motor segments ensure greater range of spine motion. It is characterized by three degrees of motion: flexion-extension, bending from side to side, rotation around central axis.

The structure of joints

Joints – movable connection of bones, primary purpose of which is to reduce friction between bones. If there were no buffering mechanisms in the joints, our movements in such case where reminiscent, short and sharp as movements of a robot. However, each step or movement would cause pain due to bone rubbing against bone.

How are joints constructed?
The creation of the joint may involve two bones and it is called simple joint connection (e.g.: knuckles). Or three bones – a complex joint (elbow, ankle).
Outside joint is limited by the capsule, which forms a closed cavity. Connections strengthen joint mobility and limit it from unnecessary movements . The surfaces of the bones are covered with articular cartilage – tissue that reduces friction during movements. Articular capsule contains of synovial bursa which produces a liquid, that moisturizes and nourishes cartilage.

Does all joints have the same structure?
According to the principle described above, instilled so-called “uniaxial joints”, they make moves only within the same plane (e.g. flexion-extension, as knuckles), their joint surfaces perfectly match each other. Joints that are responsible for movement in different planes, with a complex organization are:

1. Articular surfaces do not match each other in size or shape. In such joints there are cartilaginous additional anatomical structures – menisci and lips that adapt to the inconsistencies in the form of joint and their surfaces (meniscus), increase joint surface (lip) in size and inconsistencies with shock-absorbing properties that reduce the load on the bone.
2. In the cavity there may be additional (intra) ligaments.
3. The joint capsule forms a twist by which it can stretch more at large amplitude of motions.
4. Around the complex joints there are more additional closed structure, such as synovial bursas. They are closed or connected to the articular cavity bags constructed similarly to the articular capsule, located mainly on the surface of bone or between tendons; this function reduces friction between articular tissues.

What are the most common joint diseases?
Osteoarthritis, arthritis, traumas.

 

Muscles and tendons

Movement – basic property of all living, and the muscles play active role in it. Movement, regardless of amplitude, is an integral function of the body, determined by the reduction and relaxation of muscles. Muscles in a human body make up to 40-50% of its weight.

How muscle are built?
Base of each muscle is the connective “skeleton” – a set of membranes that combine muscle and form tendons towards the end. These membranes are attached with muscle fibers that while reduction are responsible for movement. The implementation of the muscles requires orders from the brain. So, each individual fiber is attached with nerve ending (receptor).

What tasks do muscles have?
Their main function is to provide movements. In addition, muscles are involved in heat creation. Also muscles contribute to metabolism between tissues and reduction improves blood flow in the vessels.

What are the diseases of muscles?
Important component of muscles are tendons. They are built of connective tissue bundles, that are parallel to the force of muscle contraction. Tendons are fixed on the bones, mainly within the joints and can be very long, pass muscle contraction beyond the moving part of body. For example, to move your fingers, muscle contraction passes along the whole wrist, long tendons of muscles, located on the forearm and fixed near elbow. These tendons have additional sliding apparatus, which produces a small amount of fluid and reduces friction during movement.

What are tendon diseases?
Tendons are formations, vulnerable to particular overloads. Overloads are causing pathological rebuilt (tendinosis) or inflammation (tedynit, tenosynovitis, enthesitis).

Ligaments

Ligament – a soft tissue formation, which often are located within the joints. Their main function is limitation of movements. There are ligaments that support internal organs (liver, spleen, etc.).

By its construction ligaments are similar to tendons, they consist of connective fibrous tissues, placed in parallel to the force of stretching. The main property of ligaments is elasticity (ability to stretch within certain limits and return to its original shape as a result of the termination of the tensile strength).

Nerves

Movement of the body and functioning of our body is possible only due to participation and control of the Central Nervous System.

Nerves are information conductors on the status of organs, they send signals to the brain about the temperature of the environment, touch and position of limbs. Brain analyzes the information and transmits command to the organ through nerves (backwards).

The functioning of the nervous system occurs reflexly (without consciousness) or deliberately (for example: muscle contraction during walking or everyday work).

What is the structure of nerves?
Nerve cell is wander in our body. It consists of a body, where basic processes for cell activity occur and it regulates the processes of analysis and synthesis of information. Each nerve cell has several appendages that conduct signals. Nerve cell appendage ends with the receptor that receives signal from stimulation (touch, damage) or sends an order for action (reduction or muscle relaxation).

What can be diseases of nerves?
At the base of heart diseases there is violation of nerve impulses, as a result of inflammation (neuritis), nerve root compression from outside (compression neuropathy) or inside (tumors). Often nerves may be damaged by soft tissue injuries or bone fractures.

Bones

The bones are about 20% of body weight. They form the skeleton, and some of them act as support while transferring body weight. They protect vital organs also. For example, the skull protects brain, rib – limits the chest cavity and thus protects heart and lungs. To perform these functions, bones are created especially strong. In particular, femur is so strong that it is able to hold upright the weight of one ton. And with every step load on this bone exceeds for 3 times the weight of the body. For example, when athlete-jumper jumps the landing load exceeds to 1400 kg per centimeter of bone.

Bone is build on the principle, which highly qualified builder use: combination of greatest strength at a minimum input of material. Bone tissue consists of 50% water, 20-30% – organic and only 21.85% inorganic matter (calcium, magnesium, phosphorus, etc.). It is known that steel is considered to be robust and reliable material because it is strong and flexible. Interesting fact – our bones are much stronger than steel, 10 times more elastic and lighter.

What makes bone so strong?
Bone structure captures by its perfection. This is confirmed by numerous studies, including anatomy, professor Hoffman von Mayer, that studied the structure of the femur in a place, where it is bent and enters into angled part of the hip joint. Bone does not break under the weight of the body. On the cuts professor found, that the femoral head contains a grid, organized in line of miniature plates through which the load has ability to redistribute. This net has a strict geometric structure that in 1886 engineer Gustave Eiffel used, during the construction of famous tower.
Due to the high content of organic matter, bone of health person has elastic properties, which allow it to bend in some areas during load.

Why bones are so special?
Another bone feature – plasticity or ability to change. Its restructuring is carried out continuously in equilibrium with the processes of destruction and formation of new tissue. When pressure exceeds, bones become stronger through enhancing bony plates formation. So, early and progressive load promotes rapid healing of fractures. Conversely, prolonged immobilization of a limb causes atrophy and bone strength reduction due to calcium loss ( up to 0,3 g daily).

Why do bones break?
Lets look at the example of tibia fractures: tibia feature provides withstand of heavy loads along the axis, but twisting of fixed foot may be fracture cause, and local application of force (strong blow with a stick perpendicular to the axis of the bone) will lead to a breakdown. Described reasons are not physiological, so healthy bone damage is regrettable accident. Bone fracture occurs as a result of traumatic factor that exceeds the strength of the bone. It should be noted, that the strength of the bone may decrease as a result of many pathological states also. (often osteoporosis).

Legs – support for body

Only people have ability to walk on 2 legs and this is the condition for his/her personal liberty. Without this ability, person loses autonomy and becomes dependent on others.

Load is passed from the body and may increase while carrying of heavy objects. That is why function of the lower limbs, is not only to provide transportation, but to reduce depreciation of weight of the upper half of the body. These dampening properties provide work of knee cartilage (meniscus) and an arch of foot.

Shape of legs is distinguished as follows: straight, X-shaped and O-shaped. Straight legs- longitudinal axis of the femur and tibia match, inner surfaces of the knee joint and ankle joints coincide. If only feet touch with knees joints and between ankles joint of closed legs there is certain distance, these legs are called X-shaped. Conversely, when closed ankle knee joints are apart, these legs are called O-shaped. The magnitude of forms violation of legs can be measured in centimeters between your knees (the value of O-similarity) or between ankle joints (the value of X-similarity).

Hands – organ for work

Due to the vertical position of the human body person has two free limbs that do not carry load. Hand of any person is wonderful “tool” that not only has the ability to lift, capture, catch objects, etc., but it is sense organ with the help of which we understand the world, get information about size, shape, temperature of items. We use hands to communicate (gesturing or writing a letter).With hands we keep the balance of the body, while moving in space (walking, running).

Age-related differences in structure of the locomotor apparatus

During the growth, development, aging or complex reactions, provided environmental conditions our body changes.

The Osteoarticular apparatus is not something permanent and unchangeable . Throughout life it constantly rebuilds, changes its shape, structure and functionality. The locomotor apparatus presented not only as one normal, average or most common option, it is a range of individual variants with certain age characteristics.

During childhood tissues are elastic, contain a lot of water and have rapid metabolism, that change in shape and size. Completion of growth occurs at the age of 25 years. Period up to 50 years is characterized with balance between the processes of formation and decay of tissues. In older ages body metabolism gets slower, elasticity reduces as well as water in them, ability to recover lowers.

Individual features of locomotor apparatus structure depend on inherited characteristics that define shape (feet, limbs, etc.), size (height) and function (increased mobility of the joints).

Each age period characterizes by certain diseases: in childhood diseases have dysplastic nature – development disturbs, in older age – degenerative (destabilized recovery).

Conditions of life and work can affect shape of the locomotor apparatus, by adapting to the change of muscle mass, bone strength, deformations (scoliosis) or disease (arthritis). Bone responds to changes in load increase (loader) or decrease (man in space) of strength.