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me 3 | Tissues | Learning Outcomes | J The students will be able to: * Explain the concept of tissues and their importance in multicellular life. Describe the levels of organisation in living organisms from cells to tissues. Distinguish between plant and animal tissues and relate their structures to their functions. identify and compare types of plant tissues and explain the function of each type. Describe major types of animal tissues and relate structure with function. Understand the basic components of the musculoskeletal system and the role of joints, muscles and bone; in movement. Explain the importance of posture, nutrition and exercise for musculoskeletal health and approaches to recovery from injuries. EME Tissues A tissue is a group of cells that have a similar ori organism. The study of tissues is called histology. A good example of a tissue is the epidermis, which is made up of epithelial cells. These cells generally have a similar structure, although their shape may change due tg local pressure. The main function of the epidermis is to protect the underlying cells. After repeated mitotic cell divisions, many daughter cells are formed. These cells arrange themselves ing definite pattern to perform a specific function, leading to the formation of a tissue. During the development an organism, these tissues undergo differentiation, by which cells become specialised for particular functions In multicellular organisms, different tissues perform specialised functions efficiently. This is known as divisior of labour. Tissues together form organs, and organs combine to form organ systems. This organisation ensure better functioning and survival of the organism due to increased structural complexity. In contrast, in a unicellular organism, all life processes are carried out by a single cell. Some tissues are simpl in structure, while others are complex in structure. gin and structure and perform a specialised function in a, Levels of Organisation oo fo \ Sy / XS ‘Cel Tissue Organ Organ system Organism A cell is the basic structural and functional unit of a living organism. Example: Nerve cell ) —— ———— ———— A tissue is a group of cells having a common origin, similar structure and function and | by pementing subs e. Exe tive J held together by a cementing substance. Example: € “onnective tissu a) and contributing to specific functions inside the body constitute an organ. Example: Stomach J Different organs coordinate to perform a specific life process and form an organ system. Various organ systems working simultaneously together constitute an organism. Example: Humans a and Animals Have Similar Tissues? yo Plants nimals do not have similar types of tissues. It is because of the differences in their habit, qants and a and energy requirements. All plants are fixed to a place, whereas the animals are seen to iganisation place to another (mobile) for food, shelter and mating. So, they need specialised tissues, nove for organ systems to keep the animals living. The complexity in the structure of tissues and their pgans an eerore complicated in animals than in the complex plants. jonil unctto me Differences between Plant and Animal Tissues ma Plant tissues Animal tissues 5, No- f the plant tissues are simple, supportive and in Serer, they need less maintenance and do not consume energy- Most of the animal tissues are living. Therefore, they are complex and need regular maintenance and energy. They are simple in their structural organisation. They are complex in their structural organisation. They are adapted for a sedentary (fixed) existence of plants. So many cells/tissues are dead. They are adapted for a motile (motion) and existence of animals. So many cells/tissues are living and help in locomotion, e.g., muscle cells. are two types of tissues. One is specialised for ret where growth is localised and the other is specialised for structure and special functions. There are four types of tissues. No tissue is specialised for growth as growth is uniform in animals. Plant Tissues the tissues that are present in plant body are called plant tissues. They can be broadly grouped into two yroups. t 4 Apical Complex meristematic permanent tissue tissue ¥ | Parenchyma | [ Collenchyma | [Sclerenchyma | ‘Aim: To study the growth of roots in onion bulbs and understand the role of the root tip in root growth Materials Required: Two jars or wide-mouthed bottles, water, two onion bulbs, blade, scale/ruler Procedure: }. Take two glass jars (A. B) and fill them with water. 2 Place one onion bulb on each jar, so that the base of the bulb touches the water. 7 Label Jar A as Control and Jar B as Experiment. re Observe the growth of roots in both bulbs daily for a few days. \ j } I 5. Measure the lengti of roots on Day 1, Day 2, Day 3 and Day 4 using a scale. \ 6 On Day 5, cut the root tips of the onion bulb in Jar B (Experiment) by about I cm. Keep the bulb back in the jar. . 7. Observe the roots in both jars daily and measure th ir lengths for the next five days. (A) 8) § Record all observations in a table like the one below = Ts Length of Roots in Jar A (Control) (cm) Length of Roots in Jar B (Experiment) (cm) ww + Roots grow only when the root tips are intact. * Root growth occurs due to dividing cells at the root tip. © The root apex contains meristematic tissue, which is responsible for growth Precautions: « Ensure the water level just touches the base of the onion bulbs, not submerging them completely. © Use clean jars to avoid fungal or bacterial growth. * Handle the blade carefully while cutting the root tips to avoid injury. Permanent Tissue The newly formed cells, after some time become mature after differentiation. Such cells do not divide. Thes cells are then called permanent tissue cells. They form the plant body. They are divided into two types: 1. Simple Permanent Tissue } Simple permanent tissues are composed of only one type of similar cells. These cells do not divide ar a are usually involved in basic functions such as support, storage, and photosynthesis. Examples simple permanent tissues include parenchyma, collenchyma, and sclerenchyma. Functions of Simple Permanent Tissue Cells According to the st i i , arid Structure and position of the cells in the plant body, they show different INCHiog * Protection to the plant body from external factors or environment. * Strength and mechanical support to the plant body. * Storage of food and water. * Photosynthesis. Types of Simple Permanent Tissue Simple Permanent issues originate from meristematic tissue. Their cells lose the power of division ap, perform specialised functions. They are of three types: parenchyma, collenchyma, and sclerenchym, 1. Parenchyma Structure: * They are usually living cells. * They are oval, round, polygonal or elongated cells. * They have thin cell walls. * They have dense cytoplasm, a centrally located nucleus, and a large central vacuole. * They may or may not have spaces in between the cells. They are loosely packed. Lecation: Parenchyma is widely distributed in the plant body. It is found in lower plants, soft parts of plants such as the cortex and pith of stems and roots, leaves, fruit pulp, and storage organs. Functions: * It stores food materials such as starch and sugars. * It stores waste products like gums, resins, tannins, crystals, water, and inorganic wastes. ¢ It provides mechanical support to plant parts due to the turgidity of cells. + It forms the basic or fundamental tissue of many plant organs. * Some parenchyma cells retain the ability to divide and help in healing and regeneration. Parenchyma containing chlorophyll is called chlorenchyma, which helps in photosynthesis Parenchyma with large air-filled spaces is called aerenchyma, commonly found in aquatic plants, where it provides buoyancy. 2. Collenchyma Structure: © They are living cells. e They are oval, circular or polygonal cells. * They have thin cell walls, which are thickened at the corners. The thickening occurs at the corners where many cells join together. The thickness is due to cellulose and pectin material. * They do not have or have very little intercellular spaces. That is, they are densely packed. * They have chloroplasts. Location: Collenchyma is found in the peripheral regions of stems, below the epidermis, along the stem axis, petioles, and leaf stalks. Functions: « It provides mechanical support and elasticity to growing plant parts. « It allows plant parts to bend without breaking. * When chloroplasts are present, it also helps in photosynthesis. Strwcture: The cells of complex permanent tissues are dissimilar in structure, Each type of cell contributes in a specific way to the overall worki Functions: The main function of complex permanent tissues is transportation. They help in the peepee of wate and mineral salts as well as prepared food to different parts of the plant body- , ed —— complex permanent tissues found in plants are xylem and phloem, which together form the vascula; tissue system, Types of Complex Permanent Tissue 1. Xylem Xylem is a conducting tissue mainly responsible for the transport of water and mineral salts. Mosi of its cells are dead, except xylem parenchyma, which is living. varying in size, shape, and function ing of the tissue. Structure: = + Xylem tracheids - long, dead, tubular cells. . * Xylem vessels (tracheae) - tube-like dead cells joined end top, crn aan end. * Xylem fibres (sclerenchyma) — provide mechanical strength. * Xylem parenchyma - living cells that store food. Location: Xylem is found in the vascular bundles of roots, stems, e s of leaves and the central region and leaves, especially in the vein of stems and roots. Vessel Functions: member « Tracheids and vessels transport water and mineral salts upward from the roots to all parts of the plant. + Xylem parenchyma stores food and helps in lateral (sideways) conduction of water. Components of xylem © Xylem provides mechanical support due to the presence of thick-walled fibres. 2 Phicem Phloem is a conducting tissue responsible for the transport of prepared food materials in plants. Most phloem cells are living, except phloem fibres. Structure: * Sieve tubes — long, living tubular cells that conduct food. * Companion cells — living cells that assist sieve tubes. * Phloem parenchyma - living cells that store food. * Phloem fibres (bast fibres) - dead cells that provide Location: Phloem is present in the vascular bundles of roots, stems, and leaves, usually on the outer side of xylem. System. They are arranged in the Plant body as vascular "form a specialised function. the arrangement is catled © form the organs of the plant body ised to pe; the specialised functi - some of secretion, and organ ons — by tissue systems in plants include protection, conduction, ae and tip. glycerine, and mi Preserved dicot stem. blade, watch glass, water, safranin stain, microscope Procedure: 1. Take a gram plant stem or a preserved dicot stem. 2 Hold the stem between your thumb and fingers and cut it z Take thin transverse sections and place them in a wat 4 Add a drop of safranin to stain the sections. 5 Mount a thin, stained section on a microscope slide. 6 Add a drop of glycerine to the section. r. Carefully cover it with a coverslip. & Observe the section under the microscope and horizontally with a blade ch glass containing water. note the different tissues. Observation: . The epidermis forms the outermost layer. & nr . Below epidermis, cortical parenchymais visible. Hypodermis * Vascular bundles are arranged in a ring, showing xylem and phloem. acer * The pith occupies the central region of the stem. Sunde Conclusion: The transverse section of a dicot stem shows distinct layers of tissues, including Pith epidermis, cortex, vascular bundles (xylem and ‘ ), and pith. TS. of dicot stem * Take thin sections to see the cells clearly under the microscope. * Handle the blade carefully to avoid injury. * Do not aliow the sections to dry; keep them in water until Staining. * Use only a small amount of safranin to avoid over-staining. * Wash off excess stain gently with water if needed. * Place the coverslip carefully to avoid trapping air bubbles. * Add only one drop of glycerine to prevent overflow. park or cork corective HsSuTe formed on the outer surface of older stems and coos ar . - wth — ce dead, tack antervetlular spaces, and have thick cell wats umpregnated og k colts & m ¢ Cork peri @ ANY aubstance. Suberin makes the cork impermestle ty wate, “ah suber bey - vith ees, thEredy preventing excessive loss of water from plant tissues ard gase® ic he cork also known as bark. forms a thick, dark brown outer covering on trees cork, ; J . asthe plant grows in thickness, internal pressure causes the cork layer to deveic op i ks Cork is formed by a secondary meristem called cork cambium (phetlogen rac B jn older stems and roots, cork replaces the epidermis, which is destroyed due to Bark of a tree Roondary growth. Location: As stems and roots grow older, the outer tissues become compressed, dead. and replaced by cork, which forms the protective outer layer. Functions and uses of cork: 1. Cork protects the underlying tissues from mechanical injury, extreme temperatures, and infection. _ 2. It reduces water loss from the plant body due to the presence of suberin. | | 3. Cork has several commercial uses. It is used for making bottle corks, insulation materials linoleum, shock absorbers, sports goods, and other products because it is light, elastic does not absorb water easily, does not react with many liquids, and is resistant to fire. Botte with core Professor Sipra Guha Mukherjee is regarded as a pioneer of plant tissue culture research in India. She is best known for her work on the production of haploid plants using pollen grains through tissue culture techniques. Her research made it ible to develop genetically pure plants in a shorter time, which is very useful in plant breeding programs. She also contributed to the understanding of cell differentiation and plant development. Her work helped improve crop varieties orner Scientist C ed modern agricultural ch in India. Prof. Sipra and strengthened m Bri research in India. Gis bes (1938-2007) Professor S. C. Maheshwari made significant contributions to the field of plant embryology and tissue culture. He conducted pioneering research on the structure, development and function of plant reproductive cells. His studies on in vitro fertilisation and embryo development helped advance knowledge of plant reproduction. Professor Maheshwari also played an important role in promoting plant tissue culture research and education in India. His work laid a strong foundation for future research in plant biotechnology and crop Prot. S.C : Maheshwari improvement. (1933-2019) Let’s Revise Answer the following questions. 1. Name the three types of meristem based on their location in the plant body. 2. What are sclereids, and where are they found in plants? 3. Name the different elements of xylem and their functions. 4. How do xylem and phloem work together in the vascular system of plants? 5. Mention two protective functions of cork in plants. Astmal Thowet Cane re present menial dy ar called ania! Somes | be Cuboddal i be Cos +? Areolar i > Canute > Adipose Le Glandular be Bone +> Tendon t> Ligament “> Cartilage Epithelial Tissue 3 These tissues form the outermost and innermost lining of body surfaces. The cells forming this tissue are called epithelial cells. Structure of Epithelial Tissue 1. Epithelial tissues are classified based on the shape, size, and function of their cells. 2. They are formed of epithelial cells which are arranged in a layer. The cells are closely packed without any intercellular spaces. The nuclei of the cells appear to be arranged in a line. The cells rest ona basement membrane. It is an extracellular fibrous membrane that separates the epithelium from the — underlying tissue. The epithelial cells are fixed to it by a cementing material. 3. Epithelial cells may form a single layer, called simple epithelium, or multiple layers, called compound or stratified epithelium. d anctions of Epithelial Tissue 1. It forms the outer and inner lining of most organs and the alimentary canal. 2. It protects the underlying tissues from drying, bacterial infection, chemical effects, and injury. |, It helps in functions such as respiration, excretion, and absorption of materials in the body. . It helps in the secretion of various body fluids. . Itacts as a barrier or checkpoint. All materials must cross this tissue during entry into or exit from the _ body. Therefore, it plays an important role in regulating the exchange of materials between the body _ and the external environment and between different parts of the body. (c} Glandular epithelial tisswe: Glandular epithelial tissue consists of specialised epithelial cells that are modified for secretion. These cells are usually formed by the infolding of epithelial tissue to form gland-like structures. The cells are rich in cytoplasm and possess prominent nuclei to support secretory activity. Glandular epithelium is found in salivary glands, sweat glands, gastric glands of the stomach, liver, pancreas, and other glands of the body. Its Glandular epithelium main function is the secretion of various substances such as enzymes, hormones, saliva, sweat, and digestive juices. 2. Compound Epithelium The epithelial tissue made up of more than one layer of cells is called compound epithelium. The cel; are multi-layered or stratified, and the lowermost layer of epithelial cells rests on the basemen, membrane. The cells present in this tissue may be cuboidal or squamous and are arranged in Mon than one layer. The main function of compound epithelium is protection. ()) Stratified squamous epithelium: In stratified squamous epithelium, squamous epithelial cells form the superficial layers, while the deeper layers consist of cuboidal or columnar cells. This tissue is found in the inner lining of the oesophagus and pharynx, where it provides protection against wear and tear. Stratified squamous (i) Stratified cuboidal epithelium: In stratified cuboidal epithelium, cuboidal cells are present in the superficial layers. This tissue is found in the inner lining of pancreatic and salivary ducts, where it mainly helps in protection. Stratified cuboidal (ii) Stratified keratinised squamous epithelium: In stratified keratinised squamous epithelium, the squamous cells contain a protein called keratin, which is insoluble in water. Due to the presence of keratin, the cells become dry, scaly, and horny. This tissue is found in the skin and helps to prevent wear and tear. Its main function is protection against heat, mechanical injury, and dehydration. Connective Tissue As the name suggests, connective tissue is the tissue that connects various cells and tissues. Thus, it is : defined as the tissue that connects, binds, and supports various cells and tissues of the animal body. Stratified keratinised squamous ; Structure of Connective Tissue 1. Connective tissue consists of a ground substance called matrix. It is a non-cellular and non-livin intercellular substance. 2. The matrix or ground substance may be fluid, semi-fluid (jelly-like), or rigid (hard). 3. It contains different types of cells. 4. It has fibres suspended in the matrix. Functions of Connective Tissue 1. It binds cells and tissues of other organs; therefore, it is also called packing tissue. 2. It forms the structural framework of the body and provides support to the body. 3. It protects delicate organs, helps in tissue repair, stores fats, and protects the body. of Connective Tissue Depending on the type of the matrix, jelly-like, dense (rigid) or fluid connective tissue is further classified 1. Connective Tissue Proper Connective tissue proper is the general type of connective tissue. It helps in binding or packing of cefls Types of connective tissue Proper include areolar tissue, adipose tissue, tendon, and ligament. () Areolar Connective Tissue Structure: Itis a loose connective tissue. It lodges pee, /_Firctten air bubbles when this tissue is separated from the : body, hence the name loose or areolar connective tissue. It has fibroblasts, Macrophages, and mast cells. It also has fibres—elastic and collagen fibres. Location: It is located beneath the skin and muscles, on hollow visceral organs, around the walls of blood vessels, nerves, and in bone marrow. Function: Packing the spaces between the cells, repair of tissues and organs in the body cavity. (ii) Adipose tissue Structure: It is a loose connective tissue. It has fat-storing cells called adipocytes and other cells suspended in the matrix. It also has collagen and elastic fibres that run across the tissue. Location: Around delicate organs like the heart and kidney. It is also present beneath the skin, around blood vessels, in bone marrow, in the hump of camels, and in the neck of rats. Function: It gives protection to delicate organs, Adipose tissue packs the space between tissues, acts as a shock absorber, supportive tissue and insulator, and provides a surface for attachment of muscles. (iii) Tendon Structure: It is a dense connective tissue in bundles. Tough, white, non-elastic bands (fibres) are secreted by the surrounding connective tissue cells. Location: These bands are present at the ends of muscles. Function: It attaches muscles to bones. (iv) Ligament Structure: It is dense connective tissue. Yellow, elastic, and very flexible bands. Location: These bands are present at the joints of bones. Functions: They join bone to bone at movable joints and give flexibility to the joints. (v) White fibrous connective tissue aoe Attachment of tendons Location: Present at joints between skull bones. and ligaments Function: Makes these joints immovable. (vi) Yellow fibrous connective tissue Location: Present in ligaments, blood vessels, and lungs. Function: Provides strength and remarkable elasticity. -_—~ Spongy bone Location: Skeleton of the organicm. It is non-flexible and the toughest tisswe of the body — Periostea! blood vessel Perforating canal bE Compact bone LS. of long bone showing compact and spongy bone tissue. Functions: 1. Bones and cartilage form the skeletal system of the body, giving a proper shape to the body. 2. The skeletal system—bones and cartilage — protects delicate organs from injury, e.g., the skull protects the brain. 3. Compact bones store calcium salts. 4. Yellow bone marrow stores fats. 5. Red bone marrow produces blood cells, hence it is red in colour. General Plan of Connective Tissue in Animal Matti Fi Cell: Function of Semi-solid, jelly like | Present Present Binding and packing Hard in bone hyaline | Absent Present osteocytes Framework of the body- connective tissues | jelly, semi-solid Present Present chondrocyte | skeleton, protection Absent but RBCs, WBCs and Transportation of appear during | platelets various materials. Life blood clotting line in the body tones are dynamic tissues that constantly undergo remodeling, where old bone is broken down by cells called osteoclasts, nd new bone is formed by osteoblasts. This helps in repairing micro-damages and maintaining strength. It also plays an nportant role in regulating calcium levels in the body. (Fluid Connective Tissue) type of connective ude areolar tissue, 3, Vascular Connective Tissue Connective tissue proper is the general Types of connective tissue propeT incl «) Blood Blood is the fluid connective tissu blood vessels. It is red in colour tissue. It helps in binding or packing of celig adipose tissue, tendon, and ligament. s from one part of the body to another throug, e of the body. It flow: ce called haemoglobin, a protein because of a substan Structure: (a) Blood has a liquid part called blood plasma, which acts as the matrix. It makes up about 55% of the total blood volume. It contains inorganic and organic compounds. Organic substances include soluble proteins — albumin (maintains osmotic pressure), globulins (some act a antibodies), and fibrinogen (used in plood clotting)—as well as glucose, amino acids, lipids vitamins, enzymes, wastes, hormones, digested food, and gases to be transported. Function of Plasma: Helps in transportation, blood clotting, immunity, and maintaining osmoti: tension in blood. (b) Blood contains three types of cells: RBCs (Red Blood Corpuscles), WBCs (White Blood Corpuscles)_ and blood platelets. « Red Blood Corpuscles containing red pigment haemoglobin. nucleated, and biconvex. In mammals, and lack nuclei, allowing them to carry is 120 days in humans, after which they are renewe count is about 5 million per cubic mm in males and 4.5 million If their number falls below this, the person becomes anaemic, (RBCs): RBCs are the most numerous blood cells and contain the iron In most vertebrates, erythrocytes are oval-shaped : erythrocytes are circular, biconcave, dise-shaped more haemoglobin. The average lifespan of RBC din red bone marrow. The norma per cubic mm in femal appears pale, and ti easily. White Blood Corpuscles (WBCs): WBCs are of two types - granulocytes and agranulocy Granulocytes have irregularly shaped nucleiand cytoplasmic granules with specific propertie. This group includes basophils, eosinophils (acidophils), and neutrophils. Agranulocytes have no cytoplasmic granules and include monocytes and lymphocytes These cells are present in 5,000-9,000 per cubic mm of blood in adult humans. They have lifespan of 2-3 days, and new cells are produced in red bone marrow. Function: WBCs fight diseases by producing antibodies and engulfing germs. « Blood Platelets: Platelets are minute, anucleated, fragile fragments of giant bone marrow ¢ called megakaryocytes. They are small, irregularly shaped bodies in blood, numbe! about 2,50,000 per cubic mm in humans. They have a lifespan of 7 days. Function: Platelets help in blood clotting. tissue fu (ii) Lymph Jar connective tissue present in lymph vessels and also form: Lymph is a white vascul around body tissues. Function: * Carries materials from tissues « The WBCs present in lymph dest to the bloodstream and vice versa. roy invading microorganisms. 1. Smooth Muscles Structure: . Smooth muscle cells are spindle-shaped (pointed at both ends) with a single nucleus present in central thicker part of the cell. ; * The cells are elongated. * The cytoplasm of the muscle cells is called sarcoplasm, and the cell membrane is called ; . The sarcoplasm contains very fine myofibrils that run along the longitudinal axis of the ceils, are attached at the tips. * These muscles do not show stripes or striations across the fibres. Location: Visceral organs, blood vessels, bronchi, ureter, and iris (dark-coloured part of the eye). Functions: * Forms visceral organs, urinary bladder, and walls of blood vessels. * Helps in contraction and relaxation of the organs. 2. Striated Muscles Structure: * These muscles have long, unbranched, cylindrical fibre-like cells arranged in bundles. * They have many nuclei situated towards the periphery, making them multinucleated. * The cells appear to have light and dark bands; hence they appear striped. * The myofibrils in these cells form the light and dark bands. Location: Muscles attached to bones. Functions: * Forms the musculature of the body. * Attached to the bones of the skeleton. * Helps in movement of body parts and the body. Striated muscles 3. Cardiac Muscles Structure: Nucleus Straten * Cylindrical and branched muscles. « Have 1-2 nuclei present in the centre. * Show faint striations similar to striped muscles. Location: Forms the heart. Functions: Helps in pumping blood through the heart. Cardiac muscles ‘Spindle shaped ceils Nuc Smooth muscies Nerve Tissue Nerve tissue is made up of long nerve cells called neurons. These cells may be a metre long and remail_ connected to each other. They are present in bundles to form a nerve and are held in place by connects? tissue between them. The point where one neuron connects to another neuron is called synapse. Structure: 1, Made up of nerve cells (neurons). 2. Each neuron has three main parts: leus, and . Cell Body (Cyton): Round or polygonal in shape. Contains cytoplasm, a large central nucleus: a nucleolus. The cytoplasm has granule-like structures called Niss! granules drites: Thread-like projections arising from the cell body One projection is cal (singular), and multiple projections are called dendrites (plural). . axon: A single, long, thick extension of the cell body. The cytoplasm inside axon terminates in terminal branches ending in club-shaped structures called buttons led a dendron is called axoplasm The Neuron-a unit of nervous tissue Location: Brain, spinal cord, and nerves. Functions: 1, Forms the nervous system of the body (brain, spinal cord, and nerves). 2. Conducts, transmits, and receives messages throughout the body. 3. Controls the body. Types of Nerves There are two types of nerves: L Myelinated Nerve Fibres% « These fibres are white in appearance due to the myelin sheath covering them. ® Such nerves are called myelinated or insulated nerves. « They carry messages to and from the brain and spinal cord very fast. inated, which helps rapid transmission of Wonder Box Signals in neurons travel at speeds up to 120 meters per second, faster than a race car. ¢ Many nerves in the peripheral nervous system are myel impulses. They are similar to electric wires with a plastic or rubber coating. 2. Non-Myelinated Nerve Fibres: « These fibres are grey in colour and lack a myelin sheath, hence called non- myelinated fibres. « They are present in the centre of the brain and spinal cord. * They are similar to electric wires without a coating. BB Musculoskeletal System 1e musculoskeletal system is the body system that gives the human body its shape, pport, flexibility and ability to move. It is made up of different parts that work gether as a team. These include the skeleton (bones), muscles, joints, cartilage, ‘aments and tendons. All these components are connected and coordinated by 2 nervous system so that the body can perform various movements smoothly d with balance. 
