TNPSC BIOLOGY (ENGLISH)
WHAT IS TRANSPORT SYSTEM?
The Transport system
When living organisms get more complex, simple diffusion is no longer sufficient and more elaborate ways of transporting oxygen and material is needed. In plants, the transport systems are known as the phloem and xylem (vascular system). In humans and other animals, the transport system is made up of blood, blood vessels and a muscular pump (the heart).
Molecules move in and out of a cell through the cell membrane, which forms the boundary of each cell. The cell membrane is selectively permeable to substances, which means that it permits entry and exit of certain molecules only. The movement of molecules takes place by diffusion, osmosis, and active transport.
Molecules move out from their region of higher concentration to the region of lower concentration. Osmosis is the movement of water molecules from a region having more water molecules to a region having less water molecules when separated by a semi permeable membrane. No energy is spent during diffusion or osmosis.
In active transport, molecules have to move (against concentration gradient), i.e., from a region of their lower concentration to a region of their higher concentration. Energy is required in active transport.
Transport of Water
Roots of plants take up water and minerals from the soil. The upward movement of water and minerals termed “ascent of sap” is against gravity and is due to transpiration pull. Transpiration is the process in which a lot of water evaporates (as water vapour) from pores on the surface of leaf called stomata. This evaporation creates a vaccum and pulls up water through the xylem.
Transport of Food Material
Sugars and other food molecules synthesized in the leaves are transported to other parts of the plant through phloem. Transport of food material from leaves to other parts of the plant is called translocation. This food may be stored in fruits, stem or roots.
Transport in Animals
In the body of majority of animals, substances are transported from one part of the body to another through blood. Thus, blood is the “tissue for transport” and circulates throughout the body. Circulatory system consists of organs, which make blood circulate throughout the body. Blood transports nutrients, respiratory gases, hormones and waste material form one part of the body to another.
Human Circulatory System
Human circulatory system constrains of
(i) Centrally located muscular pump called heart, and
(ii) Blood vessels, which are tube – like structures, connected to the heart.
Open blood vascular system
✦ In open type, the blood is pumped by the heart into the blood vessels that opens into blood spaces(cavities).There is no capillary system. e.g. most arthropods. These cavities are called haemoccoel. The pressure of the blood here is very low e.g Cockroach
Closed blood vascular system
✦ The blood is circulating through the blood vessles and it creates blood pressure inside the blood vessels e. g. human blood vascular system.
✦ The heart is a hollow, muscular organ. It is somewhat conical in shape, The heart is covered with double walled membrane called pericardium. The space between the pericardial membrane is called pericardial space, which is filled with pericardial fluid.
✦ The pericardial fluid protects the heart from shock. The heart is placed inside the thoracic chamber in between the two lungs in the mediastinum
✦ The total volume of blood in blue whale is 12 tonnes. It can be pumped by its heart
Blood vessels are of three kinds:
1. Arteries: Carry blood from heart to various parts of body.
2. Veins: Bring blood from various parts of body to the heart.
3. Capillaries: Thin vessels between the artery and the vein. The capillaries allow the exchange of materials between blood and tissues.
How Heart Works?
Heart is a powerful muscular organ lying between lungs in the upper part of thoraxof our body. It is four – chambered two (right and left) atria (sing, atrium, also called auricles), and two (right and left) ventricles.
Blood vessels connected with heart
Valves in heart
1.Tricuspid valve: Located in between right atrium and right ventricle
2.Bicuspid Valve(Mitral valve):Lies in between left atrium and left ventricle
3.Semi lunar valves :Present near the mouth of pulmonary artery and aorta
Difference between artery and vein
It carries blood from the heart to the organs
It carries blood from the organs to the heart
It carries oxygenated blood except pulmonary artery
It carries deoxygenated blood except pulmonary veins
The wall is thick and elastic
The wall is thin and less elastic
It is found deep inside the muscles
It is found superficially
Valves are absent
Valves are present
Conduction of Heart Beat
The Heart is made of cardiac muscles. The walls of the ventricles are much thicker than walls of the atria. A specialized cardiac musculature, called the nodal tissue, is also distributed in the heart. The detail of these nodal tissues is as follows:
SA Node: The sino – atrial Node (SA Node) is present in the right upper corner of the right atriucm. AV Node: The atrio – ventricular node is present in the lower left corner of the right atrium, close to the atrio – ventricular septum.
Bundle of His: A bundle of nodal fibers, called atrio – ventricular bundle (AV Bundle), continues from the AVN and passes through the artio – ventricular septa to emerge on the top of the inter – ventricular spetum. Then, this bundle divides into a right and left bundle. These branches give rise to minute fibers throughout the ventricular musculature of the respective sides and are called Purkinje fibers. These fibers, along with right and left bundles, are known as the Bundle of His.
The whole cycle is repeated. One cardiac cycle = 0.8 seconds. Stroke Volume: The volume of blood pumped by the heart in one cardiac cycle is called stroke volume. This is about 70 ml. Cardiac Output: The volume of blooded pumped by the heart in one minute is called the cardiac output. The average cardiac output is 5000 ml or 5 litre per minute.
Electrocardiograph (ECG): The graphical representation of the electrical activity of the heart during a cardiac cycle is called ECG.
Each peak in the ECG is identified with a letter from P to T (PQSRT) which corresponds to a specific electrical activity of the heart.
1. The P-Wave represents the electrical excitation or depolarization of the atria. Depolarization of atria leads to atricular systole.
2. The QRS complex represents the depolarization of the ventricles which initiates ventricular systole.
3. The T – Wave represents the return of the ventricles from excited to normal state (repolarisation). The end of T – Wave marks the end of systole.
Any deviation in the normal PQRST pattern of ECG indicates towards possible heart ailment.
Disorders of Circulatory System
High blood pressure (Hypertension): The Normal blood pressure in human beings is 120/80 mm Hg. If the blood pressure is more than this range, this condition is called hypertension. If the blood pressure comes in the range of 140/90 mm Hg on repeated checks, then the person is diagnosed with hypertension. The higher value, i.e., 120 mm Hg shows the systolic blood pressure, while the lower value shows the diastolic blood pressure. Hypertension finally progresses into heart diseases and also affects vital organs like brain and kidney.
Coronary Artery Disease (CAD): Deposition of fat, cholesterol, calcium and fibrous tissues makes the lumen of the coronary artery narrower. This leads to coronary artery disease. Angina: This is usually called angina pectoris: which means a pain in the chest region. Myocardial Infarction: This is commonly known as heart failure. When oxygen supply is obstructed to a part of the cardiac muscle for a prolonged period of a few minutes, it ischemia and is accompanied by sudden stoppage of the heating of heart. The stoppage of the beating of heart is called heart attack or myocardial infarction.
Animals and their hearts
Blood is a connective tissue which is composed of a fluid matrix (plasma) and formed elements.
Plasma is a straw – coloured and viscous fluid. Plasma constitutes about 55% of the blood. About 90% of plasma is water and about 6 – 8% is composed of proteins. The major plasma proteins are: fibrinogen, globulins and albumins. Plasma also contains glucose, amino acids, lipids, etc. because these substances are always in transit in the body.
The formed elements constitute about 45% of the blood. Erythrocytes, leucocytes and platelets are collectively called formed elements. Erythrocytes or Red Blood Cells (RBCs): The RBCs are the most abundant cells in blood. In a healthy adult, about 5 million to 5.5 million RBCs are present per cubic mm of blood. RBCs are formed in the read bone marrow in the adults. In most of the mammals, nucleus is absent in the RBCs. RBCs are biconcave n shape. The red colour is because of an iron containing protein complex: called haemoglobin. The life span of RBC is 120 days.They are destroyed in the liver and spleen.
Leucocytes or White Blood Cells (WBCs): The WBCs are nucleated and are relatively lesser in number than RBCs. In a healthy adult about 6000 – 8000 WBCs are present per cubic mm of blood. Leucocytes are generally shortlived. The lifespan of WBC is 4 weeks.
Platelets: Platelets are also known as thrombocytes. They are cell fragments produced from megakaryotcytes. Megakaryocytes are special cells in the bone marrow.
Functions of Blood
1. Blood distributes the digested food
2. Blood carries the metabolic wastes to excretory organs
3. Blood carries hormones, which are the secretions of endocrine glands.
4. Blood distributes the heat evenly body.
5. Blood keeps all the tissues
Two such groupings – the ABO and Rh – are widely used all over the world.
ABO grouping is based on the presence of absence of two surface antigens on the RBCs, viz. A and B. Antigens are chemicals which can induce immune response. The plasma also contains two natural antibodies. Antibodies are proteins produced in response to antigens.
Blood Group and Donor Compatibiliy
Antigens on RBC
Antibodies in Plasma
Anti – B
Anti – B
Anti – A,B
The blood group O can be donated to persons with any other blood group and hence, and individual with O blood group is called a universal donor. A person with AB blood group can accept blood from all blood groups and hence, such as individual is called universal recipient.
The Rh antigen is similar to one present in Rhesus monkeys. It is also observed on the surface of RBCs of majority (nearly 80%) humans. Such individuals are called Rh positive (Rh +ve). A person without Rh antigen is called Rh negative (Rh –ve).
Rh Imcompatibility of Fetus and Mother: A special case of Rh incompatibility is observed between the Rh – ve blood of a pregnant mother with Rh +ve blood of the fetus. Rh antigens of the fetus do not get exposed to the Rh – ve blood of the mother in the first pregnancy because the two bloods are well separated by the placenta. But during the delivery of the first child, there is a possibility of exposure of the maternal blood to small amounts of Rh +ve blood form the fetus. In such an eventuality, the mother starts preparing antibodies against Rh in her blood.
In case of her becoming pregnant again. The Rh antibodies from the mother (Rh –ve) can leak into the blood of the fetus (Rh +ve) and destroy the fetal RBSs; This can prove fatal to the foetus or can cause severe anemia and jaundice to the baby. This condition is called erythroblastosis foetalis. This can be avoided by administering anti – Rh antibodies to the mother immediately after the delivery of the first child.
Coagulation of Blood
Coagulation is a mechanism to prevent excessive loss of blood in case of injury.
Process of Blood Clotting: Inactive fibrinogen is present in the plasma. It is converted by the enzyme thrombin into active fibrin. Thrombin is formed from the inactive prothrombin. An enzyme complex, thrombokinase, is responsible for this conversion. This complex is formed by a series of linked enzymatic reactions (cascade process). The process involves a number of factors present in the plasma in an inactive state. An injury stimulates the platelets to release certain factors which activate the mechanism of coagulation. Calcium ions play a very important role in clotting.
Haemophilia: Haemophilia is a clotting disorder which prevents blood clotting. A person suffering from haemophilia is always at a risk of excessive blood loss in case of injury.
Lymph (Tissue Fluid)
Lymph is a colourless fluid. It contains specialized lymphocytes. Lymph also carries nutrients, hormones, etc. Fats are absorbed through lymph in the lacteals present in the intestinal villi.
Excretion of Metabolic Wastes
Animals accumulate ammonia, urea, uric acid, carbon dioxide, water and irons like Na+, K+, Cl-, phosphate, sulphate, etc., either by metabolic activities or by other means like excess ingestion. These substances have to be removed totally or partially. The process of removal of these harmful substances is called excretion.
The process of excreting ammonia is Ammonotelism. May bony fishes, aquatic amphibians and awuatic insects are ammonotelic in nature.
Mammals, many terrestrial mphibians and marine fishes mainly excrete urea and are called ureotelic animals. Ammonia produced by metabolism is converted into urea in the liver of these animals and released into the blood which is filtered and excreted out by the kidney.
Reptiles, brides, land snails and insects excrete nitrogenous wastes as uric acid in the form of pellet or paste with a minimum loss of water and are called uricotelic animals.
Different Types of Excretory Organs in Animals
Protonephridia or flame cells are the excretory structures in Platyhelminthes. Protonephridia are primarily concerned with ionic and fluid volume regulation, i.e., osmoregulation.
Nephridia are the tubular excretory structures of earthworms and other annelids. Malpighian tubules are the excretory structures of most of the insects including cockroaches.
Antennal glands or green glands perform the excretory function in crustaceans like prawns.
Human Excretory System
In human, the excretory system consists of a pair of kidneys, one pair of ureters, a urinary bladder and a urethra.
Shape & Size: Kidneys are reddish brown, bean shaped structures situated between the levels of last thoracic and third lumbar vertebra close to the dorsal inner wall of the abdominal cavity.
Structure: Towards the centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter.
Inner Structure: Inside the kidney, there are two zones, an outer cortex and an inner medulla. The medulla is divided in to a few conical masses (medullary pyramids) projecting into the calyces (sing: calyx). The cortex extends in between the medullary pyramids as renal columns called Column of Bertini.
Nephrons: Each kidney has nearly one million complex tubular structures called nephrons, which are the functional units. Each nephron has two aprts – the glomerulus and the renal tubule.
Glomerulus: Glomerulus is a tuft of capillaries formed by the afferent arteriole – a fine branch of renal artery. Blood from the glomerulus is carried away by an efferent arteriole. The renal tubule begins with a double walled cup – like structure called Bowman’s capsule, which encloses the glomerulus. Glomerulus alongwith Bowman’s capsule, is called the malpighian body or renal corpuscle.
Tubules: The tubule continues further to form a highly coiled network – proximal convoluted tubule (PCT). A hairpin shaped Henle’s loop is the next part of the tubule which has a descending and an ascending limb. The ascending limb continues as another highly coiled tubular region called distal convoluted tubule (DCT) The DCTs of many nephrons open into a straight tube called collecting duct, many of which converge and open into the renal pelvis through medullary pyramids in the calyces. The Malpighian corpuscle, PCT and DCT of the nephron are situated in the cortical region of the kidney whereas the loop of Henle dips into the medulla.
Cortical Nephrons: In majority of nephrons, the loop of Henle is too short and extends only very little into the medulla. Such nephrons are called cortical nephrons.
Urine Formation: Urine formation involves three main processes namely:
1. Glomerular Filtration
2. Reabsorption, and
Regulation of Kidney Functions:
The functioning of the kidneys is efficiently monitored and regulated by hormonal feedback mechanisms involving the hypothalamus, JGA and to a certain context, the heart.
Osmoreceptors in the body are activated by changes in blood volume, body fluid volume and ionic concentration. An excessive loss of fluid from the body can activate these receptors which stimulate the hypothalamus to release antidiuretic hormone (ADH) or vasopressin from the neurohypophysis. ADH facilitates water reabsorption from latter parts of the tubule, thereby preventing dieresis.
An increase in body fluid volume can switch off the osmoreceptors and suppress the ADH release to complete the feedback.
Role of other organs in excretion
Lungs: Lungs remove large amount of CO2 (18 litres/day) and also significant quantities of water every day.
Liver: Liver, the largest gland in our body, secretes bile containing substances like bilirubin, biliverdin, cholesterol, degraded steroid hormones, vitamins and drugs. Most of these substances ultimately pass out along with digestive wastes.
Skin: The sweat and sebaceous glands in the skin can eliminate certain substances through their secretions. Sweat produced by the sweat glands is a watery fluid containing NaCl, small amounts of urea, lactic acid, etc. Sebaceous glands eliminate certain substances like sterols, hydrocarbons and waxes through sebum. This secretion provides a protective oily covering for the skin.
Skin has three layers:
Epidermis: (the outermost layer of skin, provides a waterproof barrier and creates our skin tone). The epidermis contains five layers. From bottom to top the layers are named:
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum licidum
5. Stratum corneum
Dermis: (The dermis, beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands. The dermis is composed of three types of tissue that are present throughout – not in layers. The types of tissue are:
1. Collagen, 2. Elastic tissue and 3. Reticular fibers
Subcutaneous: The deeper subcutaneous tissue (hypodermis) is made of fat and connective tissue. The subcutaneous tissue is a layer of fat and connective tissue that houses larger blood vessels and nerves. This layer is important in the regulation of temperature of the sin itself and the body.
Disorders of the excretory system
Kidney failure: Malfunctioning of kidneys can lead to accumulation of urea in blood, a condition called uremia, which is highly harmful and may lead to kidney failure.
Renal Calculi: Stone or insoluble mass of crystallized salts (oxalates, etc.) formed within the kidney. These produce severe pain if they result in obstruction of urethra.
The nervous system of all animals is composed of highly specialized cells called neurons which can detect, receive and transmit different kinds of stimuli.
The roles of the nervous system are: responsible for coordination of movement, response to environmental stimuli, intelligence, self – awareness, thought, emotion. Composed of nerve cells called neurons, which are specialized to carry nerve impulses. The human nervous system is divided into two parts:
(i) Central Nervous System (CNS)
(ii) Peripheral Nervous System (PNS)
Neuron as Structural and Functional Unit of Nervous System
A neuron is a microscopic structure composed of three major parts, namely, cell body, dendrites, and axon.
Cell Body: The cell body contains cytoplasm with typical cell organelles and certain granular bodies, called Nissl’s granules.
Dendrites: Short fibers which branch repeatedly and project out of the cell body also contain Nissl’s granules and are called dendrites. These fibers transmit impulses towards the cell body.
Axon: The axon is a long fiber, the distal end of which is branched. Each branch terminates as a bulb – like structure called synaptic knob which possess synaptic vesicles containing chemicals called neurotransmitters. The axons transmit nerve impulses away from the cell body to a synapse or to a neuro – muscular junction.
Based on the number of axon and dendrites, the neurons are divided into three types:
a) Multipolar (with one axon and two or more dendrites; found in the cerebral cortex),
b) Bipolar (with one axon and one dendrite, found in the retina of eye) and
c) Unipolar (cell body with one axon only , found usually in the embryonic stage).
There are two types of axons, namely, myelinated and non – myelinated. The myelinated nerve fibers are enveloped with Schwann cells, which form a myelin sheath around the axon.
Central Nervous System The brain is the central information processing organ of our body, and acts as the command and control system. It controls the voluntary movements, balance of the body, functioning of vital involuntary organs (e.g., lings, heart, kidneys, etc), thermo – regulation, hunger and thirst, circadian (24 hour) rhythjms of our body, activities of several endocrine glands and human behavior. It is also the site for processing of vision, hearing, speech, memory, intelligence, emotions, and thoughts.
The brain can be divided into three major parts:
(ii) Midbrain, and
The forebrain consists of cerebrum, thalamus and hypothalamus. Cerebrum forms the major part of the human brain. A deep cleft divides the cerebrum longitudinally into two halves, which are termed as the left and right cerebral hemispheres. The hemispheres are connected by a tract of nerve fibers called corpus callosum. The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds. The cerebral cortex is referred to as the grey matter due to its grayish appearance. The neuron cell bodies are concentrated here giving the colour.
The cerebrum wraps around a structure called thalamus, which is a major coordinating centre for sensory and motor signaling. Another very important part of the brain called hypothalamus lies at the base of the thalamus. The hypothalamus lies at the base of the thalamus. The hypothalamus contains a number of centres which control body temperature, urge for eating and drinking.
Midbrain The midbrain is located between the thalamus / hypothalamus of the forebrain and pons of the hindbrain. A canal called the cerebral aqueduct passess through the midbrain. Midbrain and hindbrain form the brain stem.
Hindbrain The hindbrain comprises pons, cerebellum and medulla (also called the medulla oblongata). Pons consists of fiber tracts that interconnect different regions of the brain.
✦ Cerebellum regulates and coordinates the group movements of voluntary muscles as in walking or running.
It relays the information from from the cerebrum to cerebellum. It alsocontains sleep centre and respiratory centre
✦ Medulla is the centre for several reflexes involved in the regulation of heartbeat, blood vessel contraction,breathing, etc,.
✦ The ventricle of the medulla remains connected with the ventricles of the cerebral hemisphere
The Spinal cord
✦ This is a tubular structure, a continuation of the brain lying in theneural canal of the vertebral column.
✦ The lower end of the spinal cord is filamentous and is called Filumterminale.
✦ Running through the center of the spinal cord is the central canal, anextension of the ventricle filled with cerebro spinal fluid.
Peripheral nervous system (PNS)
✦ The nerves arising from the brain and spinal cord constitute the PNB.
✦ Twelve pairs of cranial nerves arise from the brain.
✦ Thirty one pairs of spinal nerves arise from the spinal cord.
The Autonomic Nervous System (ANS)
In controls the functions of the vital organs of the body through its twoantagonistic divisions namely, sympathetic and parasympatheticnerves.
Reflex Action and Reflex Arc
You must have experienced a sudden withdrawal of a body part which comes in contact with objects that are extremely hot, cold pointed or animals that are scary or poisonous. The entire process of response to a peripheral nervous stimulation, that occurs involuntarily, i.e., without conscious effort or thought and requires the involvement of a part of the central nervous system is called a reflex action.
The skeletal system gives the body its basic framework, providing structure, protection, and movement the 206 bones in the body also produce blood cells, store important minerals, and release hormones necessary to life.
Types of Bone
Long Bones: These bones typically have an elongated shaft and two expanded ends, one on either side of the shaft.
Short bones: These are short in posture and can be of any shape.
Flat bones: These bones are flat in appearance and have two prominent surfaces. They resemble shallow plates and form boundaries of certain body cavities. Examples include scapula, ribs, sternum, etc.
Spongy bone: The part of a bone where bone substance to bone space ration is a smaller quantity. This means that there is more empty space and less bone tissue.
Irregular bones: The shape of these bones is completely irregular and they do not fit into any category of shape.
Pneumatic bones: Pneumatic bones can also be categorized under the irregular bones because they are also irregular in shape but since there is a difference between the two that is characteristically very important. Therefore they are often classified separately. The characteristic difference is the presence of large air spaces in these bones.
Sesamoid bones: These are not like the other types of bones because they are in the form of nodules embedded in tendons and joint capsules. They do not possess any periosteum and their ossification also takes place after birth. Examples of this type of bones are patella, pisiform and fabella.
Macroscopic approach divides the bones into two categories that are:
Compact bone: The part of a bone where bone substance to bone space ration is a bigger quantity is called compact bone. This means the there is more bone tissue and less empty space.
Types of Joints in the Skeletal System
A joint is the connection between two bones. The skeletal system is made of different types of joints, including Fibrous (immoveable), Cartilaginous (partially moveable) and the Synovial (freely moveable) joint.
The fibrous (fixed or immovable) joints in the skeletal system include the sutures of the skull. The coronal suture connects the parietal and frontal skull bones.
Cartilaginous joints are partially movable joints consisting of symphyses or synchondroses joints. Examples of cartilage nous types of joints include the rib cage and the spinal column.
Ball – and – Socket Joint
Mercksource.com, an online medical dictionary, describes a ball – and – socket joint as one in which the rounded surface of a bone fits into and moves within a cup – shaped depression.
The Saddle joint is a biaxial joint that allows movement on two planes – flexion / extension and abduction / adduction. The thumb is the only bone structure in the human body with a saddle joint.
Hinged joints include the elbow, fingers, toes and knee. Movement occurs in only one direction or one plane.
Gliding joints allow two or more flat or slightly rounded bones to move easily together without friction or grinding.
A pivot joint is a synovial joint designed with one end fitting like a cylinder inside a ring.
Condyloid Joints are biaxial joints that permit up, down and side – to – side motion.
The skeletal system consist of bones, cartilages and ligaments. It is a frame on which all organs are arranged.
The human skeletal system is divided into two categories
✦ The axial skeleton
✦ The appendicular skeleton.
✦ Skull consist of 22 bones. Among 22 , 8 are head bones and remaining 14 are facial bones.
✦ The skull is divided into head bones and facial bones.
✦ The cranium is covered by 8 bones. All are flat bones. They are joined with immovable joints. It protects the brain.
✦ The thoracic cavity consists of three different types of bones.
✦ The front portion has single bone named sternum.
✦ The back portion has a long vertebral column.
✦ Both the bones are connected by ribs on the lateral side.
✦ There are 12 pairs of ribs.
✦ In the front, the first ten pairs are attached with sternum.
✦ The first seven pairs are directly attached with sternum. They are called as the true ribe.
✦ Cartilages of 8th ,9th and 10th are fused and attached to the sternum indirectly. They are called false ribs.
✦ They are called floating ribs.
The vertebral column vertebrae
✦ Actually back bone consist of 33 vertebrae. They are divided into five regions.
Vertebral column of a human
✦ Cervical vertebrae – 7
✦ Thoracic vertebrae – 12
✦ Lumbar vertebrae – 5
✦ Sacral vertebrae – 5
✦ Cocygeal vertebrae – 4
Upper limb or hands
✦ Upper arm has a long bone named humerus. The distal end of the upper arm is articulate with two fore arm bones named ulna and radium.
✦ The frame work of the hand if formed of five metacarpels. Each hand have five digits. They include one thumb and four fingers. Each digit has small long bones called phalanges.
The pelvic girdle and leg
✦ The pelvic girdle is a ring of bones in the hip region formed by scarum and paired bones called coxae or hip bones.
✦ Each coxa is formed by the fusion of three bones namely ilium, ischium and pubis. The thigh region contains the longest bone called femur.
✦ The ankle consist of seven tarsal bones. The ankle articulates with tibia and fibula through talus.
Number of bones in human body
✦ In the human body, there are 206 bones of those 80 are in the axial skeleton, 126 are in the appendicular skeleton 28 bones are in the skull, 26 are in the vertebral column, 25 bones are in the thoracic cage and one remains as the hyoid bone.
Human Body and its movements
✦ Bone is a hard, grayish-white substance of which, two thirds is composed of inorganic matter or minerals like Calcium, phosphate, Carbonate which make the bone more brittle. The remaining one third is organic matter.
✦ Bones are not solid. They have a strong outer layer of light weight compact bone which is spongy inside
✦ In the centre a soft marrow which makes new Red Blood Cells(R BC) for the blood
✦ Bones hav a strong covering like skin, this outer layer is called periosteum
✦ The adult human skeleton consists of 206 bones.They are classified into axial skeleton and appendicular skeleton.
✦ The vertebral column has a characteristic curve. It has five distinct regions.
They are listed below.
1. Cervical Region (neck region) consists of seven vertebrae
2. Thoracic Region (chest region) consists of twelve vertebrae
3. Lumbar Region (Abdominal region) consists of five vertebrae
4. Sacral Region (Hip region) consists of five vertebrae
5. Coocygeal Region (vestigial region) consists of four vertebrae. They are rudimentary.
Ribs and sternum (Ribcage)
✦ Protect the vital organs like lungs, heart, etc., There are twelve pairs ofribs.
✦ The ribs at the sides, the sternum in the front and the backbones togetherform the “chest box"
✦ The first seven pairs of ribs are directly attached to the sternum and are called ‘true ribs’
✦ The next three pairs of ribs which are not directly attached to the sternum are called ‘false ribs’
✦ The last two pairs (11th and 12th) are short and not connected to the sternum they are called ‘floating ribs’
Functions of the SkeletalSystem
✦ Support provideframe work and supports the soft tissue.
✦ Protection: Many vital internal organs like brain, heart, lungs areprotected.
✦ Movement facilitation: Serves as lever and helps to produce movement
✦ Storage of minerals: Stores minerals like calcium, phosphate and carbonate.
✦ Production of blood cells: Bone marrow produces the RBC, WBC andblood platelets.
More to know
✦ The largest bone in the human body is the thigh bone or femer. In an average man, it is about 45 cm long.
✦ The smallest bone is the Shapes, inside the ear.
Movement of Animals
✦ Fishes live only in water. Their stream-line bodies are best suited for locomotion in water. Fins are locomotion organs
✦ Most fish swim by waving their tails from side to side (eg. Tunny fish) .
✦ Eels are fish with long bodies and moving with its whole body from side to side.
✦ By moving certain fins, fish can change direction .They can go up or down, from left to right, or from right to left
✦ The earth worm moves at the rate of 25 cm per minute.
✦The nervous coordinates the activities of circular and longitudinalmuscles.
✦ Cockroach is a swift runner as well as a flier.
✦ The six legs are helpful in walking or running. When the cockroach is atrest, the coxae of the legs lie back against the body and the first legs are.directed forward.
✦ The hind legs are stretched out posterior and the middle legs takewhatever position is convenient.
✦ This S-shape movement also known as undulatory locomotion is used by many snakes on land and in water.
✦ Birds are best suited for an aerial mode of life. The body is stream-linesand thus offers the least amount of resistance for movement in the air.
✦ The reduced body weight facilitates easy flight. This is brought about bythe hollow (pneumatic) bones and air sacs in the cavity of the bone.