Body_Tissues fully detailed notes [1].pptx

Body tissues all in one best notes for exams point of view.

1. Body Tissues BY Dr. Uzma Saleem

2. Tissue The word tissue comes from an old French verb meaning “to weave”. Tissue is a group of similar cells, having same origin and performing a specific function. The term tissue was given by Bichat. The study of tissue is known as histology. The term histology was introduced by Mayer. Xavier Bichat   ("the father of histology") establishes the systematic study of tissues as a discipline within anatomy by describing twenty-one basic tissue types. Karl Mayer applies the word "histology" as the name for the new discipline founded by Bichat.

3. History of Bichat Xavier Bichat , who lived a short life (1771–1802), was prominent French anatomist and physiologist during the time of revolution . He played a key role in the creation of the science of histology.  Indeed, he was the first to see the organs of the body as being formed through the specialization of simple, functional units (tissues). Bichat is also known as one of the last of the major theorists of vitalism . [ Vitalism is a scientific theory that living organisms have a vital force, or life-force, that is distinct from physical and chemical forces, and that this force controls the development and activities of living organisms].

4. History of Karl Mayer Karl Mayer (1787–1865) was a German anatomist and physiologist who coined the term "histology" in 1819. The term comes from the Greek words histos (tissue) and logia (science). Mayer used the term in his book on histology and a new classification of tissues of the human body.

5. Types of tissues The organs in your body are composed of four basic types of tissue, including: Epithelial Connective Muscular Nervous

6. Epithelial Tissue Epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Epithelial tissues covers body surface, lines body cavities & ducts and form glands. The epithelium is a type of body tissue that forms the covering on all internal and external surfaces of the body, lines body cavities and hollow organs and is the major tissue in glands. Epithelial tissue has a variety of functions depending on where it’s located in your body, including protection, secretion and absorption.

7. There are many different kinds of epithelial tissue throughout the body. Some examples of epithelial tissue include: The outer layer of the skin (epidermis) The lining of the intestines The lining of the respiratory tract The lining of the abdominal cavity Sweat glands Epithelial cells derive from following three major embryonic layers: Ectoderm Mesoderm Endoderm

8. The epithelia lining the skin, parts of the mouth, nose and anus develop from ectoderm . The epithelium that lines vessels in the lymphatic and cardiovascular system derives from mesoderm and is called an endothelium .

9. General characteristics This tissue is highly cellular. Little or no extracellular material present between cells. Adjoining cells form a specialized intercellular connection between their cell membrane called cell junction. The basal lamina, a mixture of glycoproteins and collagen provides an attachment site for the epithelium separating it from underlying connective tissue. The basal lamina attaches to a reticular lamina (collagen and elastin), which is secreted by the underlying connective tissue, forming a basement membrane that helps hold it all together.

10. 6. Epithelial tissues are nearly completely avascular. For instance no blood vessels cross the basement membrane to enter the tissue. 7. Nutrients must come by diffusion or absorption from underlying tissues or surface. 8. Many epithelial tissues are capable of rapidly replacing damaged and dead cells. 9. Sloughing off of damaged or dead cells is a characteristic of surface epithelium and allows our airways and digestive tracts to rapidly replace damaged cells with new cells.

11. Generalized function of Epithelial tissues Epithelial tissues provide the body’s first line of protection from: Physical Chemical, and Biological wear and tear. The cells of an epithelium act as gatekeepers of the body controlling permeability and allowing selective transfer of materials across a physical barrier. Some epithelia often include structural features that allow the selective transport of molecules and ions across their cell membranes.

12. 4. Many epithelial cells are capable of secretion and release mucous and specific chemical compounds onto their apical surface. 5. The epithelium of the small intestine releases digestive enzymes.

13. Epithelial Tissue

14. Cell surfaces The cells of epithelial tissue have three types of surfaces differentiated by their location and functional specializations: i ) basal, ii) apical, and iii) lateral Basal surface The basal surface is nearest to the basement membrane. The basement membrane itself creates a thin barrier between connective tissues and the most basal layer of epithelial cells. Specialized junctions called hemi desmosomes secure the epithelial cells on the basement membrane.

15. Lateral surface The lateral surfaces of epithelial cells are located between adjacent cells. The most notable lateral surface structures are junctions. Adhering junctions link the cytoskeleton of neighboring cells to produce strength in the tissue. Desmosomes can be thought of as spot- welding for epithelial tissues. They are usually located deep to adhering junctions and are found in locations subject to stresses. For example in the stratified epithelium of the skin . 3. Apical surface The apical surface of an epithelial cell is nearest to the luminal or free space. Apical cell surfaces may display specialized extensions.

16. Cilia are microscopic extensions of the apical cell membrane that are supported by microtubules. Microvilli are small processes projecting from the apical surface to increase surface area. They are heavily involved in diffusion in the PCT of the nephron and in the lumen of the Small Intestine.

17. The Epithelial Cell Epithelial cells are typically characterized by the polarized distribution ( this is the organization of proteins and lipids on the plasma membrane of cells. It's essential for the physiological functions of eukaryotic cells and gives them distinct identities ) of organelles and membrane-bound proteins between their basal and apical surfaces. Particular structures found in some epithelial cells are an adaptation to specific functions. Certain organelles are segregated to the basal sides, whereas other organelles and extensions, such as cilia, when present, are on the apical surface.

18. Functions: Move fluids as well as trapped particles. Helps in circulation of cerebrospinal fluid. Ciliated epithelium of airway forms mucociliary escalator that sweeps dust particles. It is called an escalator because it continuously pushes mucous with trapped particles upward. Nasal cilia sweep the mucous blanket down towards your throat. 6. In both cases, the transported materials are usually swallowed, and end up in the acidic environment of your stomach.

19. Cell-Cell Junction Cells of epithelia are closely connected and are not separated by intracellular material. Three basic types of connections allowing varying degrees of interaction between the cells: Tight Junctions Anchoring Junctions Gap Junctions

20. Tight junction They separates the cell into apical & basal compartments. When two adjacent epithelial cells form a tight junction, there is no extracellular space between them and the movement of substances through the extracellular space between the cells is blocked. This enables the epithelia to act as selective barriers.

21. 2. A nchoring junction An anchoring junction includes several types of cell junctions that help stabilize epithelial tissues. Anchoring junctions are common on the lateral and basal surfaces of cells where they provide strong and flexible connections. There are three types of anchoring junctions: Desmosomes Hemidesmosomes Adherens

22. Desmosomes occur in patches on the membranes of the cell. These patches are structural proteins on the inner surface of cell’s membrane. The adhesion molecule, cadherin, is embedded in these patches and projects through the cell membrane to link with the cadherin molecules of adjacent cells. ii. Hemidesmosome , look like half of desmosome & link cells to the extracellular matrix for instance, the basal lamina. Includes adhesion protein called integrins .

23. iii. Adherens junction They use either cadherins or integrins depending on whether they are linking to other cells or matrix. These junctions are characterized by the presence of the contractile protein actin located on the cytoplasmic surface of the cell membrane. These junctions influence the shape and folding of the epithelial tissue.

24. 3. Gap junction They forms an intercellular passage way between the membranes of adjacent cells to facilitate the movement of small molecules and ions between the cytoplasm of adjacent cells. These junctions allow electrical and metabolic coupling of adjacent cells, which coordinates function in large groups of cells.

25. Classification of Epithelial tissues Epithelial tissues are classified according to Shape of the cell Number of cell layers formed 1. Classification based on cell shape Squamous (flattened & thin) Cuboidal (boxy, as wide as it is tall) Columnar (rectangular, taller than it is wide)

26. 2. Classification based on number of cell layers Similarly, the number of cell layer in the tissue can be one, where every cell rest on basal lamina, it is called simple epithelium . If number of cell layer is more than one. It is called stratified epithelium & only the basal layer of the cell rests on basal lamina. 2.1. Simple epithelialium Squamous epithelium (flattened) Cuboidal epithelium (cube shaped) Columnar epithelium (elongated) Ciliated epithelium Pseudo-stratified epithelium

27. 2.2. Compound or Stratified epithelium Stratified compound Transitional compound Pseudostratified Pseudostratified (Pseudo = false) describes tissues with single layer of irregularly shaped cells that give the appearance of more than one layer.

28. I . Simple epithelium : The cells in simple squamous epithelium have the appearance of thin scales. Squamous cell nuclei tend to be flat , horizontal , and elliptical (oval shape). Example: The endothelium is the epithelial tissue that lines vessels of the lymphatic and cardiovascular system & it is made up of single layer of squamous cell. Simple squamous epithelium, because of the thinness of the cell, is present where rapid passage of chemical compounds is observed.

29. Other Examples are: Alveoli of lungs where gases diffuse Segments of kidney tubules Lining of capillaries Simple squamous epithelium of alveoli Simple squamous epithelium of kidney

30. Simple squamous epithelium of blood vessel

31. Example: The Mesothelium is a simple squamous epithelium that forms the surface layer of the serous membrane that lines body cavities and internal organs. Its primary function is to provide a smooth and protective surface. Mesothelial cells are squamous epithelial cells that secrete a fluid that lubricates the mesothelium and reduce the friction between organs and the walls of body cavities .

32. II. Simple cuboidal epithelium : The nucleus of the box-like cells appears round and is generally located near the center of the cell. These epithelia are active in the secretion and absorptions of molecules. Examples: Simple cuboidal epithelia are observed in the lining of the kidney tubules and in the ducts of glands. Kidney Pancreatic duct

33. III. Simple Columnar epithelium The nucleus of the tall column- like cells tends to be elongated and located in the basal end of the cells. This epithelium is active in the absorption and secretion of molecules. Simple columnar epithelium forms the lining of some sections of the digestive system and parts of the female reproductive tract.

34. IV. Ciliated columnar epithelium It is composed of simple columnar epithelial cells with cilia on their apical surfaces. These epithelial cells are found in the lining of Fallopian tubes Respiratory system

35. V. Pseudostratified columnar epithelium It is a type of epithelium that appears to be stratified but instead consists of a single layer of irregularly shaped and differently sized columnar cells. In pseudostratified epithelium, nuclei of neighboring cells appear at different levels rather than clustered in the basal end. The arrangement gives the appearance of stratification; but in fact all the cells are in contact with the basal lamina, although some do not reach the apical surface. Pseudostratified columnar epithelium is found in the respiratory tract .

36. Transitional epithelium Another kind of stratified epithelium so- called because of the gradual changes in the shapes of the apical cells as the bladder fills with urine. It is found only in the urinary system, specifically the ureters and urinary bladder. When the bladder is empty, this epithelium is convoluted and has cuboidal apical cells with convex, umbrella shaped, apical surfaces. As the bladder fills with urine, this epithelium loses its convolutions and the apical cells transition from cuboidal to squamous. It appears thicker and more multi- layered when the bladder is empty, and more stretched out and less stratified when the bladder is full and distended.

37. Connective Tissue

38. Introduction As obvious from its name, one of the major function of connective tissue is to connect tissue and organs. Connective tissue cells are dispersed in a matrix . The matrix usually includes a large amount of extracellular material produced by the connective tissue cells that are embedded within it. The matrix plays a major role in the functioning of this tissue.

39. Two major components of the matrix are : Ground substance Protein fibers Ground substance : It is usually a fluid (water), but it can also be mineralized and solid, as in bones. Connective tissues come in a vast variety of forms, yet they typically have in common three characteristic components: Cells Large amount of ground substance Protein fibers

40. The amount and structure of each component correlates with the function of the tissue. Like f rom the rigid ground substance in bones supporting the body to the inclusion of specialized cells; for example, a phagocytic cell that engulfs pathogens and also rids tissue of cellular debris. Fibroblast : The most common cell found within connective tissue. Polysaccharides and proteins secreted by fibroblasts combine with extra- cellular fluids to produce a viscous ground substance that with embedded fibrous proteins, forms the extracellular matrix.

41. Types of fibers secreted by fibroblasts: Collagen Elastic Reticular Collagen fiber: It is made from fibrous protein subunits linked together to form a long and straight fiber. Flexible Great tensile strength Resist stretching, and give ligaments and tendons their characteristic resilience and strength. These fibers hold connective tissues together, even during the movement of the body.

42. Elastic fiber : It contains the protein elastin along with lesser amounts of other proteins and glycoproteins. The main property of elastin is that after being stretched or compressed, it will return to its original shape. Elastic fibers are prominent in elastic tissues found in skin and the elastic ligaments of the vertebral column.

43. Reticular fiber : It is also formed from the same protein subunits as collagen fibers. However, these fibers remain narrow and are arrayed in a branching network. They are found throughout the body, but are most abundant in the reticular tissue of soft organs, such as liver and spleen. Liver

44. Classification of Connective tissue

45. Classification of Connective tissue Loose Connective Tissue They have large amounts of ground substance and fewer fibers. Types are: Aerolar Adipose Reticular 2. Dense Connective Tissue They have large amounts of fibers and less ground substance. Types are: Dense regular Dense irregular Elastic Connective Tissue

46. 3. Cartilage Specialized cells called chondrocytes are within the matrix (cartilage cells) Hyaline cartilage Elastic cartilage Fibrocartilage 4. Bone Strongest connective tissue with little ground substance, hard matrix of calcium and phosphorous and specialized bone cells called osteocytes. 5. Blood Fluid connective tissue, no fibers – only ground substance (plasma) and cells (red, white, and platelets).

47. 1. Loose connective tissue Loose connective tissue is found between many organs where it acts both to absorb shock and bind tissues together. It allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues. Fat contributes mostly to lipid storage, can serve as insulation from cold temperatures and mechanical injuries. Example : Adipose tissue consists mostly of fat storage cells called a dipocytes that store lipids as droplets that fill most of the cytoplasm. A large number of capillaries allow rapid storage and mobilization of lipid molecules.

48. Adipose Tissue

49. 1.1. Areolar tissue This is the most generalized type of connective tissue. The matrix is semisolid with many fibroblasts and some fat cells (adipocytes), mast cells and macrophages, widely separated by elastic and collagen fibers. It is found in almost every part of the body, providing elasticity and tensile strength. It connects and supports other tissues, for example: under the skin between muscles

50. supporting blood vessels and nerves in the alimentary canal in glands supporting secretory cells. Book: Ross and Wilson

51. 1.2. Reticular tissue It is a mesh- like, supportive framework for soft organs such as lymphatic tissue, the spleen, and the liver. It contains reticular cells and white blood cells (monocytes and lymphocytes). Reticular cells produce the reticular fibers that form the network onto which other cells attach. It derives its name from the Latin word reticulus , which means “little net.”

52. Reticular tissue

53. 2. Dense connective tissue Dense connective tissue contains more collagen fibers than does loose connective tissue. As a consequence, it displays greater resistance to stretching. There are three major categories of dense connective tissue: regular, irregular, and elastic. 2.1. Dense regular connective tissue fibers are parallel to each other, enhancing tensile strength and resistance to stretching in the direction of the fiber orientations. Example: Ligaments and tendons are made of dense regular connective tissue.

54. 2.2. Dense irregular connective tissue , the direction of fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers.

55. 2.3. Elastic tissue Elastic tissue is capable of considerable extension and recoil. There are few cells and the matrix consists mainly of masses of elastic fibres secreted by fibroblasts. It is found in organs where stretching or alteration of shape is required. e.g. in large blood vessel walls, the trachea and bronchi, and the lungs.

56. 3. Cartilage Types of cartilages Hyaline cartilage Fibrocartilage Elastic cartilage i . Hyaline cartilage The most common type of cartilage in the body, consists of short and dispersed collagen fibers and contains large amounts of proteoglycans. The surface of hyaline cartilage is smooth, Both strong and flexible.

57. It is found in the rib cage and nose and covers bones where they meet to form moveable joints. It makes up a template of the embryonic skeleton before bone formation. A plate of hyaline cartilage at the ends of bone allows continued growth until adulthood. ii. Fibro cartilage It is tough because it has thick bundles of collagen fibers dispersed through its matrix. The knee and jaw joints and the intervertebral discs are examples of fibrocartilage.

58. iii. Elastic cartilage It Contains elastic fibers as well as collagen and proteoglycans. This tissue gives rigid support as well as elasticity. Tug gently at your ear lobes, and notice that the lobes return to their initial shape. The external ear contains elastic cartilage.

59. [Type of Hyaline cartilage]

60. 4. Blood Blood is a fluid connective tissues. Blood has two components: Cells Fluid matrix Erythrocytes, red blood cells, transport oxygen and some carbon dioxide. Leukocytes, white blood cells, are responsible for defending against potentially harmful microorganisms or molecules. Platelets are cell fragments involved in blood clotting. Some white blood cells have the ability to cross the endothelial layer that lines blood vessels and enter adjacent tissues.

61. Nutrients, salts, and wastes are dissolved in the liquid matrix called plasma and transported through the body. Lymph contains a liquid matrix and white blood cells. Lymphatic capillaries are extremely permeable, allowing larger molecules and excess fluid from interstitial spaces to enter the lymphatic vessels. Lymph drains into blood vessels, delivering molecules to the blood that could not otherwise directly enter the blood stream.

62. Bone

63. 5. Bone Bone is the hardest connective tissue. It provides protection to internal organs and supports the body. Bone’s rigid extracellular matrix contains mostly collagen fibers embedded in a mineralized ground substance containing hydroxyapatite, a form of calcium phosphate. Both components of the matrix, organic and inorganic, contribute to the unusual properties of bone. Without collagen, bones would be brittle and shatter easily. Without mineral crystals, bones would flex and provide little support.

64. Osteocytes , bone cells, are located within lacunae (gap). The histology of transverse tissue from long bone shows a typical arrangement of osteocytes in concentric circles around a central canal. Bone is a highly vascularized tissue. Unlike cartilage, bone tissue can recover from injuries in a relatively short time .

65. Bone is a living tissue capable of changing its structure as the result of the stresses to which it is subjected. Like other connective tissues, bone consists of: cells, fibers, and Matrix It is hard because of the calcification of its extracellular matrix and possesses a degree of elasticity because of the presence of organic fibers. Bone has a protective function.

66. Examples: The skull protect the brain and vertebral column protect the spinal cord from injury. The sternum and ribs protect the thoracic and upper abdominal viscera respectively.

67. Bone exists in two forms: Compact Cancellous Compact bone : appears as a solid mass Cancellous bone: consists of a branching network of trabeculae . The trabeculae are arranged in such a manner as to resist the stresses and strains to which the bone is exposed.

68. Classification of Bone Bone may be classified regionally or according to their general shape.

69. Classification of Bone Long Bones: are found in the limbs, for example Humerus Femur Metacarpals Metatarsals Phalanges

70. Characteristics : Their length is greater than their breadth. They have tubular shaft, the diaphysis & usually epiphysis at each end. During the growing phase, the diaphysis is separated from th e epiphysis by an epiphyseal cartilage. The part of diaphysis lies adjacent to epiphyseal cartilage is called the metaphysis. The shaft has central marrow cavity containing bone marrow. The outer part of the shaft is composed of compact bone that is covered by a connective tissue sheath, the periosteum .

71. The ends of the long bone are composed of cancellous bone surrounded by thin layer of compact bone. The articular surfaces of the end of the bones are covered by hyaline cartilage.

72. Short bones They are found in hands & feet, for example Scaphoid Lunate Talus Calcaneus They are roughly cuboidal in shape and composed of cancellous bone surrounded by thin layer of compact bone. Short bones are covered with periosteum. The articular surfaces are covered with hyaline cartilage.

73. Flat bones They are found in vault of the skull (frontal and parietal bones). They are composed of thin inner and outer layers of compact bone. The scapulae, although irregular, included in this group. The tables of the skull are the layers of compact bone that make up the cranial bones.  The skull has two tables, an outer table and an inner table, separated by a layer of spongy bone called the diploë .

74. Irregular bones include those not assigned to the previous group For example, bones of skull, the vertebrae and the pelvic bone They are composed of thin shell of compact bone with an interior made up of cancellous bone. Sesamoid bones They are small nodules of bone that are found in certain tendons where they rub over bony surfaces. The greater part of sesamoid bone is buried in the tendon & free surface is covered with cartilage. The largest sesamoid bone is patella, which is located in the tendon of the quadriceps femoris.

75. JOINTS

76. Definition: A site where two or more bones come together, whether or not movement occurs between them, is called a joint . Types: joints are classified according to the tissues that lie between the bones: Fibrous joints Cartilaginous joints Synovial joints

77. i . Fibrous joints The bones forming these joints are linked with tough, fibrous material. Such an arrangement often permits no movement. For example, the joints between the skull bones, the sutures, are completely immovable (Fig. A on next slide), and the healthy tooth is cemented into the mandible by the periodontal ligament (Fig. B on next slide). The tibia and fibula in the leg are held together along their shafts by a sheet of fibrous tissue called the interosseous membrane (Fig. C on next slide) . This fibrous joint allows a limited amount of movement and stabilises the alignment of the bones.

78. Fibrous joints: (A)Suture of the skull (B) The periodontal ligament (C) The Interosseous membrane linking the tibia and fibula

79. ii. Cartilaginous joints It can be divided into two types: ( i ) Primary (ii) secondary ( i ) Primary cartilaginous joint It is one in which the bones are united by a plate or a bar of hyaline cartilage. Example The union between epiphysis and the diaphysis of the growing bone (Fig. A on next slide) & between 1 st rib and the manubrium sterni are examples of such joints. No movement is possible.

80. Cartilaginous joints. (A) The epiphyseal plate. (B) Intervertebral discs and the symphysis pubis.

81. ii. Secondary cartilaginous joint It is one in which bones are united by a plate of fibrocartilage and articular surface of the bones are covered by a thin layer of hyaline cartilage. Examples : Joints between vertebral bodies and the symphysis pubis (Fig. B on previous slide). A small amount of movement is possible. They are also shock absorbent.

82. iii. Synovial joints Synovial joints are charcterised by the presence of a space or capsule between the articulating bones. The ends of the bones are held close together by a sleeve of fibrous tissue (fibrous sheath) and lubricated with a small amount of fluid. Synovial joints are the most movable Joints of the body. The basic structure of a synovial joint

83. Characteristics 1. The articular surfaces of the bone are covered by a thin layer of hyaline cartilage separated by a joint cavity. 2. This arrangement permits a great degree of freedom of movement. 3. The cavity of the joint is lined by synovial membrane, which extends from the margins of one articular surface to those of the other. 4. The synovial membrane is protected on the outside by a tough fibrous membrane referred to as the capsule of the joint. 5. The articular surfaces are lubricated by a viscous fluid called synovial fluid, produced by synovial membrane.

84. 6. Fatty pads are found in some synovial joints lying between the synovial membrane and the fibrous capsule or bone. e.g. hip and knee joints. Ilium:  This large, wing-shaped bone forms the upper part of the hip, providing stability and support for the joint. Ischium:  The ischium is the lower and posterior part of the hip bone. It forms the “sit bones” and supports our body weight when we sit. Pubis:  The pubis is the anterior part of the hip bone and is responsible for connecting the two hip bones at the front of the pelvis.

85. Types of Synovial Joints Synovial joints can be classified according to the Arrangement of the articular surfaces & Type of movement that are possible Plane joints The apposed (place side by side) articular surfaces are flat or almost flat, and this permits the bones to slide on one another. Examples: Sternoclavicular & acromioclavicular joints

86. Hinge joints They resembles the hinge on a door, so that flexion and extension movements are possible. Examples: elbow, knee & ankle Pivot joint A central bony pivot is surrounded by a bony-ligamentous ring and rotation is the only movement Possible Example: atlantoaxial joint

87. Condyloid joint It has two distinct convex surfaces that articulate with two concave surfaces. The movements of flexion, extension, abduction and adduction are possible together with small amount of rotation. Examples: the metacarpophalangeal joint or knuckle joint

88. Ellipsoid joints An elliptical convex articular surface fits into an elliptical concave articular surface. The movements of flexion, extension, abduction and adduction can take place, but rotation is impossible because of the presence of ligaments in a particular fashion. Example: The wrist joint is a good example.

89. Saddle joints The articular surfaces are reciprocally concavoconvex and resemble a saddle on a horse’s back. These joints permit flexion, extension, abduction, adduction, and very slight rotation. Example: carpometacarpal joint of the thumb

90. Ball- and- socket joints A ball- shaped head of one bone fits into a socket like concavity of another. This arrangement permits free movements, including Flexion Extension Abduction Adduction Lateral rotation Circumduction Examples: Shoulder & hip joint. Shoulder joint is shallower than the hip joint that’ s why shoulder dislocation is common.

91. Types of synovial joint with examples of their locations in the skeleton

92. Muscle

93. Definition A band or bundle of fibrous tissues that has the ability to contract, producing movement in or maintaining the position of parts of the body. Skeletal Muscle Skeletal muscles produce the movements of the skeleton. They are sometimes called voluntary muscles and are made up of striped muscle fibers. A skeletal muscle has two or more attachments. The attachment that moves the least is referred to as the origin , and the one that moves the most is known as the insertion.

94. The fleshy part of the muscle is referred to as its belly. The ends of a muscle are attached to bones, cartilage by cords of fibrous connective tissue called tendons. Occasionally, flattened muscles are attached by a thin but strong sheet of fibrous tissue called an aponeurosis.

95. Structure of Skeletal Muscle The muscle fibers are bound together with delicate areolar tissue, which is condensed on the surface to form a fibrous envelope, the epimysium . The individual fibers of a muscle are arranged either parallel or oblique to the long axis of the muscle. Because a muscle shortens by one third to one half its resting length when it contracts. It follows that muscles whose fibers run parallel to the line of pull will bring about a greater degree of movement compared with those whose fibers run obliquely.

96. Examples of muscles with parallel fiber arrangements are Sternocleidomastoid Rectus abdominis Sartorius Sartorius Sternocleidomastoid Sartorius Rectus abdominis

97. Muscles whose fibers run obliquely to the line of pull are referred to as pennate muscles (feather like). unipennate muscle A unipennate muscle is one in which the tendon lies along one side of the muscle and the muscle fibers pass obliquely to it. Example: Extensor digitorum longus

98. Bipennate muscle A bipennate muscle is one in which the tendon lies in the center of the muscle and the muscle fibers pass to it from two sides. Example: Rectus femoris Rectus femoris

99. Multipennate muscle They may be arranged as a series of bipinnate muscle lying alongside one another. e.g. acromial fibers of deltoid. OR They may have the tendon lying within its center & muscle fiber passing to it from all sides. e.g. tibialis anterior.

100. Acromial fibers of deltoid

101. Smooth muscle Smooth muscle (SM) consist of long, s pindle-shaped cells closely arranged in bundles or sheets. In the tubes of the body, it provides the motive power for propelling the contents through the lumen.

102. A wave of contraction of the circularly arranged fibers passes along the tube, mixing the contents onward. In the storage organ such as urinary bladder & the uterus, the fibers are irregularly arranged & intercalated with one another. In the walls of the blood vessels, the SM fibers are arranged circularly & serve to modify the caliber of the lumen.

103. Cardiac Muscle Cardiac muscle consists of striated muscle fibers that branch and unite with each other. It forms the myocardium of the heart. Its fibers tend to be arranged in spirals, they have the property of spontaneous and rhythmic contraction. Specialized cardiac muscle fibers form the conducting system of the heart. Cardiac muscle is supplied by autonomic nerve fibers that terminate in the nodes of the conducting system and in the myocardium.

104. Cardiac muscle is made up of individual cells called cardio myocytes.  Cardio myocytes are tubular in shape and contain chains of myofibrils.  Myofibrils are rod-like units that contain sarcomeres, which are the muscle's fundamental contractile units.  Cardiac muscle cells are branched, unlike skeletal and smooth muscle cells, which are linear and longitudinal.