2. AHP PPT- Unit – II Skeletal System Full- Subathra.pptx

Skeletal:
Types of Bone and function
Physiology of Bone formation
Division of Skeleton
Types of joints and function
Types of cartilage and function
Muscular
Parts of Muscle
Movements
Respiratory
Parts of Respiratory Systems
Types of respiration
Mechanisms of Breathing
Regulation of Respiration

1. Unit – II Skeletal System

2. Topic to be covered in Unit – II Skeletal: Types of Bone and function Physiology of Bone formation Division of Skeleton Types of joints and function Types of cartilage and function Muscular Parts of Muscle Movements Respiratory Parts of Respiratory Systems Types of respiration Mechanisms of Breathing Regulation of Respiration

3. Session 1

4. Objective: To understand the macroscopic and microscopic  structure  of a long  bone and its function Learning Outcome: Underline the role of bone in giving shape to the body Elucidate Sliding theory of contraction State the importance of muscles in movement

5. Skeletal System

6. Besides bones, the  skeletal system  includes cartilage and ligaments. The   skeleton  is traditionally divided into two major  parts : the axial  skeleton , which includes the skull, spine, and rib cage; the appendicular  skeleton , which includes the appendages and the girdles that attach them to the axial   skeleton . Cartilage  is a type of dense connective tissue, made of tough protein fibers. It is strong but flexible and very smooth. It covers the ends of bones at joints, providing a smooth surface for bones to move over. Ligaments  are bands of fibrous connective tissue that hold bones together. They keep the bones of the skeleton in place.

7. Axial and Appendicular Skeletons The skeleton is traditionally divided into two major parts: the axial skeleton and the appendicular skeleton The axial skeleton forms the axis of the body . It includes the skull, vertebral column (spine), and rib cage. The bones of the axial skeleton, along with ligaments and muscles, allow the human body to maintain its upright posture . The axial skeleton also transmits weight from the head, trunk, and upper extremities down the back to the lower extremities. In addition, the bones protect the brain and organs in the chest. The appendicular skeleton forms the appendages and their attachments to the axial skeleton . It includes the bones of the arms and legs, hands and feet, and shoulder and pelvic girdles. The bones of the appendicular skeleton make possible locomotion and other movements of the appendages. They also protect the major organs of digestion, excretion, and reproduction.

8. Bone- Introduction A bone is a rigid organ that constitutes part of the vertebrate skeleton. Bones support and protect the various organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, and enable mobility. Bones come in a variety of shapes and sizes and have a complex internal and external structure. They are lightweight yet strong and hard, and serve multiple functions. Bone tissue is a hard tissue, a type of dense connective tissue.

9. It has a honeycomb-like matrix internally, which helps to give the bone rigidity. Bone tissue is made up of different types of bone cells. Bone is a strong and durable type of connective tissue. It consists of : water (25%) organic constituents including osteoid (the carbon containing part of the matrix) and bone cells (25 %) inorganic constituents, mainly calcium phosphate (50%) Although bones are often thought to be static or permanent they are highly vascular living structures that are continuously being remodeled.

10. Bone structure General structure of a long bone (Fig. 16.1 ) These have a diaphysis or shaft and two epiphyses or extremities. The diaphysis is composed of compact (cortical) bone with a central medullary canal, containing fatty yellow bone marrow. The epiphysis consist of an outer covering of compact bone with cancellous (trabecular, spongy) bone inside. The diaphysis and epiphyses are separated by epiphyseal cartilages, which ossify when growth is complete. Thickening of a bone occurs by the deposition of new bone tissue under the periosteum . Long bones are almost completely covered by a vascular membrane, the periosteum . The outer layer is fibrous and the inner layer is osteogenic containing osteoblasts (bone-forming cells) and osteoclasts ( bone-destroying cells ), which are involved in maintenance and remodeling of bones; it gives attachment to muscles and tendons and protects bones from injury. Hyaline cartilage replaces periosteum on the articular surfaces of bones forming synovial joints

11. Bone structure Structure of short, irregular, flat and sesamoid bones (Fig. 16.2) These have a relatively thin outer layer of compact bone with cancellous bone inside containing red bone marrow (Fig . 16.2). They are enclosed by periosteum except the inner layer of the cranial bones where it is replaced by dura mater.

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13. Session 2

14. Objective: To understand the macroscopic and microscopic  structure  of a long  bone and its function Learning Outcome: List the types of bones based on structure Illustrate different types of bone structure

15. Bone Cells Bones are not a static tissue but need to be constantly maintained and remodeled. There are three main cell types involved in this process . Osteoblasts :  These are responsible for making new bone and repairing older bone . Osteoblasts produce a protein mixture called osteoid , which is mineralized and becomes bone. They also manufacture hormones, including prostaglandins. Osteocytes:  These are inactive osteoblasts that have become trapped in the bone that they have created. They maintain connections to other osteocytes and osteoblasts. They are important for communication within bone tissue. Osteoclasts:  These are large cells with more than one nucleus . Their job is to break down bone . They release enzymes and acids to dissolve minerals in bone and digest them. This process is called resorption . Osteoclasts help remodel injured bones and create pathways for nerves and blood vessels to travel through.

16. Functions of bones Bones have a variety of functions. They: provide the framework of the body give attachment to muscles and tendons permit movement of the body as a whole and of parts of the body, by forming joints that are moved by muscles form the boundaries of the cranial, thoracic and pelvic cavities, protecting the organs they contain contain red bone marrow in which blood cells develop : haematopoiesis provide a reservoir of minerals, especially calcium phosphate .

17. Types of bones- Shape Bones are classified as long, short, irregular, flat and sesamoid . Long bones: These consist of a shaft and two extremities. As the name suggests the length is much greater than the width . Examples include the femur, tibia and fibula. Short, irregular, flat and sesamoid bones: These have no shafts or extremities and are diverse in shape and size. Examples include: short bones — carpals ( wrist) irregular bones—vertebrae and some skull bones flat bones — sternum, ribs and most skull bones sesamoid bones — patella (knee cap).

18. Long bones Short bones Flat bones Sesamoid bones Irregular bones

19. Types of Bones & its function There are five types of bones in the human body: Long bones:  A   long bone is one that is cylindrical in shape, being longer than it is wide . Long bones are mostly compacted bone with little marrow and are found in the arms ( humerus , ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers ; they move when muscles contract. These bones tend to support weight and help movement . Short bones:  Only a thin layer of compact bone , these include bones in the carpals of the wrists and the tarsals of the ankles . Short bones provide stability and support as well as some limited motion . Flat bones:  Usually bones that are thin and curved . They consist of two outer layers of compact bone and an inner layer of spongy bone. Flat bones include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs .

20. Types of Bones & its function Sesamoid bones:  These are embedded in tendons , such as the patella or kneecap. They protect tendons from wear and stress . Irregular bones:  As their name implies, these are bones that do not fit into the first four categories and are an unusual shape . They include the bones of the spine and pelvis . They are often protecting organs or tissues. Bones of the skeleton are split into two groups: Appendicular skeleton  — bones of the limbs, shoulders, and pelvic girdle. Axial skeleton  — bones of the skull, vertebral column, thoracic cage.

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22. Session 3

23. Objective: To gain knowledge on skeleton division and its related biological terms To know the different types of joints and its function Learning Outcome: Differentiate axial and appendicular skeleton structure Differentiate between joints Recall how the joints bring about various motions

24. Division of Skeleton The skeletal system includes all of the bones, cartilages, and ligaments of the body that support and give shape to the body and body structures. The  skeleton consists of the bones of the body. For adults, there are 206 bones in the skeleton. Younger individuals have higher numbers of bones because some bones fuse together during childhood and adolescence to form an adult bone.

25. Division of Skeleton The primary functions of the skeleton are to provide a rigid, internal structure that can support the weight of the body against the force of gravity, and to provide a structure upon which muscles can act to produce movements of the body. The lower portion of the skeleton is specialized for stability during walking or running. In contrast, the upper skeleton has greater mobility and ranges of motion , features that allow you to lift and carry objects or turn your head and trunk.

26. The Axial Skeleton: The  axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back It serves to protect the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs . The Appendicular Skeleton: The appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. There are 126 bones in the appendicular skeleton of an adult.

27. Axial Skeleton This part consists of the skull, vertebral column, ribs and sternum . Together the bones forming these structures constitute the central bony core of the body, the axis . Skull (Figs 16.7 and 16.8) The skull rests on the upper end of the vertebral column and its bony structure is divided into two parts: The cranium T he face Cranium The cranium is formed by a number of flat and irregular bones that provide a bony protection for the brain . It has a base upon which the brain rests and a vault that surrounds and covers it. The periosteum inside the skull bones consists of the outer layer of dura mater . In the mature skull the joints (sutures) between the bones are immovable (fibrous). The bones have numerous perforations (e.g. foramina, fissures) through which nerves, blood and lymph vessels pass . The bones of the cranium are : 1 frontal bone 2 parietal bones 2 temporal bones 1 occipital bone 1 sphenoid bone 1 ethmoid bone .

28. Face The skeleton of the face is formed by 13 bones in addition to the frontal bone. Figure 16.13 shows the relationships between the bones : 2 zygomatic or cheek bones 1 maxilla (originated as 2) 2 nasal bones 2 lacrimal bones 1 vomer 2 palatine bones 2 inferior conchae 1 mandible (originated as 2 ) Axial Skeleton

29. Vertebral column ( Fig.16.16 ) The vertebral column consists of 24 separate movable, irregular bones, the sacrum (five fused bones) and the coccyx (four fused bones). The 24 separate bones are in three groups: 7 cervical, 12 thoracic and 5 lumbar. The movable vertebrae have many characteristics in common but some groups have distinguishing features.

30. Thoracic cage (Fig. 16.25 ) The bones of the thorax or thoracic cage are: 1 sternum 12 pairs of ribs 12 thoracic vertebrae

31. Appendicular Skeleton The appendicular skeleton consists of the shoulder girdle with the upper limbs and the pelvic girdle with the lower limbs Shoulder girdle and upper limb Each shoulder girdle consists of: 1 clavicle 1 scapula. Each upper limb consists of the following bones: 1 humerus 1 radius 1 ulna 8 carpal bones 5 metacarpal bones 14 phalanges.

32. Pelvic girdle and lower limb The bones of the pelvic girdle are: 2 innominate bones 1 sacrum. The bones of the lower limb are: 1 femur 1 tibia 1 fibula 1 patella 7 tarsal bones 5 metatarsal bones 14 phalanges. Appendicular Skeleton

33. Joints A joint, also known as an articulation or articular surface , is a connection that occurs between bones in the skeletal system. Joints provide the means for movement . The type and characteristics of a given joint determines its degree and type of movement . Joints can be classified based on structure and function .

34. Structural classification of joints Structural classification of joints categorizes them based on the type of tissue involved in formation. There are three structural classifications of joints: Fibrous Joint Cartilaginous Joint Synovial Joint

35. Fibrous Joints Fibrous joints are connected by dense, tough connective tissue that is rich in collagen fibers . These fixed or immovable joints are typically interlocked with irregular edges. There are three types of fibrous joints . Sutures are the types of joint found in the cranium (skull). The bones are connected by Sharpey’s fibres ( The outer surface of bone is covered by periosteum, which is bound to bone by bundles of collagen  fibers  known as  Sharpey's fibers , and the inner bone surface is lined with endosteum ). The nature of cranial sutures allows for some movement in the fetus. However, they become mostly immovable as the individual ages, although very slight movement allows some necessary cranial elasticity. These rigid joints are referred to as synarthrodial .

36. Contd … Syndesmoses are found between long bones of the body, such as the radio-ulnar and tibio -fibular joints. These moveable fibrous joints are also termed amphiarthrodial . They have a lesser range of movement than synovial joints. Gomphosis is a type of joint found at the articulation between teeth and the sockets of the maxilla or mandible (dental-alveolar joint). The fibrous tissue that connects the tooth and socket is called the periodontal ligament.

37. Fibrous Joints Image demonstrating the three types of fibrous joints. (a) Sutures (b) Syndesmosis   (c) Gomphosis .

38. Cartilaginous Joints Cartilaginous joints are connected by fibrocartilage or hyaline cartilage. They allow more movement than fibrous joints but less than that of synovial joints. These types of joints are further subdivided into primary ( synchondroses ) and secondary ( symphyses ) cartilaginous joints. The epiphyseal (growth) plates are examples of synchondroses . Symphyses are found between the manubrium and sternum ( manubriosternal joint), intervertebral discs, and the pubic symphysis .

39. Cartilaginous Joints Image demonstrates a synchondrosis joint with epiphyseal plate (temporary hyaline cartilage joint) indicated (a) and a symphysis joint (b). Manubriosternal joint Intervertebral Disc

40. Synovial Joints This is the most common and movable joint type in the body. These joints (also called diarthroses ) have a synovial cavity. Their bones are connected by dense irregular connective tissue that forms an articular capsule surrounding the bones’ articulating surfaces. A synovial joint connects bones with a fibrous joint capsule that is continuous with the bones’ periosteum. This joint capsule constitutes the outer boundary of a synovial cavity and surrounds the bones’ articulating surfaces. Synovial cavities are filled with synovial fluid. The knees and elbows are examples of synovial joints.

41. Functional Classification of Joints Functional classification of joints is based on the type and degree of movement permitted.

42. Three Categories of Functional Joints Synarthrosis :  These types of joints are immobile or allow limited mobility. This category includes fibrous joints such as suture joints (found in the cranium) and gomphosis joints (found between teeth and sockets of the maxilla and mandible). Amphiarthrosis :  These joints allow a small amount of mobility. Most joints in this category include cartilaginous joints such as those found between vertebrae and the pubic symphysis . Diarthrosis : These are the freely-movable synovial joints. Synovial joints are further classified based on the different types of movement they provide, including: Plane joint Ball and socket joint Hinge joint Pivot joint Condyloid joint Saddle joint

43. Types of joints and function : Fixed Joint or Synarthroses Slightly Movable Joint or Amphiarthroses Freely Moveable Joint or Synovial Joints Ball and socket joint Hinge joint Pivot joint Ellipsoid/gliding joint Saddle joint

44. Gliding joints: only allow sliding movement Hinge joints: allow flexion and extension in one plane Pivot joints: allow bone rotation about another bone Condyloid joints: perform flexion, extension, abduction, and adduction movements Saddle joints: permit the same movement as condyloid joints and combine with them to form compound joints Ball and socket joints: allow all movements except gliding

45. Movement of Synovial Joints Joints can also be classified by the number of axes of movement they permit: Nonaxial (gliding): Found between the proximal ends of the ulna and radius. Monoaxial (uniaxial): Movement occurs in one plane. An example is the elbow joint. Biaxial: Movement can occur in two planes. An example is the wrist. Multiaxial : Includes the ball and socket joints. An example is the hip joint. The movements possible with synovial joints are: Abduction: movement away from the body’s midline Adduction: movement toward the body’s midline Extension: straightening limbs at a joint Flexion: bending the limbs at a joint Rotation: a circular movement around a fixed point

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48. Session 4

49. Objective: To gain knowledge on cartilage and its function Learning Outcome: Differentiate various types of cartilages based on its characteristics List different types of cartilages Tabulate the functions of all types of cartilages

50. Cartilage Cartilage is a much firmer tissue than any of the other connective tissues; the cells are called chondrocytes and are less numerous. They are embedded in matrix reinforced by collagen and elastic fibres . There are three types: hyaline cartilage fibrocartilage elastic fibrocartilage .

51. Hyaline cartilage Hyaline cartilage appears as a smooth bluish-white tissue. The chondrocytes are in small groups within cell nests and the matrix is solid and smooth .

52. Fibrocartilage This consists of dense masses of white collagen fibres in a matrix similar to that of hyaline cartilage with the cells widely dispersed. It is a tough, slightly flexible tissue

53. Elastic cartilage This flexible tissue consists of yellow elastic fibres lying in a solid matrix. The cells lie between the fibres. It forms the pinna or lobe of the ear, the epiglottis and part of the tunica media of blood vessel walls.

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55. Session 5

56. Objective: To understand the mechanism behind Bone formation & growth Learning Outcome: Summarize the bone formation & the growth of bone cells List the steps involved in bone formation & bone growth during different process

57. Bone Formation and Development In the early stages of embryonic development , the embryo’s skeleton consists of fibrous membranes and hyaline cartilage. By the sixth or seventh week of embryonic life, the actual process of bone development, ossification (osteogenesis), begins. There are two osteogenic pathways: intramembranous ossification endochondral ossification But in the end, mature bone is the same regardless of the pathway that produces it .

58. Intramembranous Ossification During intramembranous ossification, compact and spongy bone develops directly from sheets of mesenchymal (undifferentiated) connective tissue . The flat bones of the face, most of the cranial bones, and the clavicles (collarbones) are formed via intramembranous ossification. The process begins when mesenchymal cells in the embryonic skeleton gather together and begin to differentiate into specialized cells (Figure 6.4.1a). Some of these cells will differentiate into capillaries, while others will become osteogenic cells and then osteoblasts. Although they will ultimately be spread out by the formation of bone tissue, early osteoblasts appear in a cluster called an ossification center. The osteoblasts secrete osteoid, uncalcified matrix consisting of collagen precursors and other organic proteins, which calcifies (hardens) within a few days as mineral salts are deposited on it, thereby entrapping the osteoblasts within. Once entrapped, the osteoblasts become osteocytes (Figure 6.4.1b). Figure 6.4.1 – Intramembranous Ossification: Intramembranous ossification follows four steps. (a) Mesenchymal cells group into clusters, differentiate into osteoblasts, and ossification centers form. (b) Secreted osteoid traps osteoblasts, which then become osteocytes.

59. Intramembranous Ossification As osteoblasts transform into osteocytes, osteogenic cells in the surrounding connective tissue differentiate into new osteoblasts at the edges of the growing bone. Several clusters of osteoid unite around the capillaries to form a trabecular matrix, while osteoblasts on the surface of the newly formed spongy bone become the cellular layer of the periosteum (Figure 6.4.1c). The periosteum then secretes compact bone superficial to the spongy bone. The spongy bone crowds nearby blood vessels, which eventually condense into red bone marrow (Figure 6.4.1d). The new bone is constantly also remodeling under the action of osteoclasts (not shown). Figure 6.4.1 – Intramembranous Ossification: Intramembranous ossification follows four steps. (c) Trabecular matrix and periosteum form. (d) Compact bone develops superficial to the trabecular bone, and crowded blood vessels condense into red bone marrow.

60. Endochondral Ossification In endochondral ossification, bone develops by replacing hyaline cartilage . Cartilage does not become bone. Instead, cartilage serves as a template to be completely replaced by new bone. Endochondral ossification takes much longer than intramembranous ossification. Bones at the base of the skull and long bones form via endochondral ossification. In a long bone, for example, at about 6 to 8 weeks after conception, some of the mesenchymal cells differentiate into chondroblasts (cartilage cells) that form the hyaline cartilaginous skeletal precursor of the bones (Figure 6.4.2a). This cartilage is a flexible, semi-solid matrix produced by chondroblasts and consists of hyaluronic acid, chondroitin sulfate, collagen fibers, and water. As the matrix surrounds and isolates chondroblasts , they are called chondrocytes . Unlike most connective tissues, cartilage is avascular, meaning that it has no blood vessels supplying nutrients and removing metabolic wastes. All of these functions are carried on by diffusion through the matrix from vessels in the surrounding perichondrium, a membrane that covers the cartilage , a ). Figure 6.4.2 – Endochondral Ossification: Endochondral ossification follows five steps. (a) Mesenchymal cells differentiate into chondrocytes that produce a cartilage model of the future bony skeleton. (b) Blood vessels on the edge of the cartilage model bring osteoblasts that deposit a bony collar. (c) Capillaries penetrate cartilage and deposit bone inside cartilage model, forming primary ossification center. (d) Cartilage and chondrocytes continue to grow at ends of the bone while medullary cavity expands and remodels. (e) Secondary ossification centers develop after birth. (f) Hyaline cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage .

61. Endochondral Ossification As more and more matrix is produced, the cartilaginous model grow in size. Blood vessels in the perichondrium bring osteoblasts to the edges of the structure and these arriving osteoblasts deposit bone in a ring around the diaphysis – this is called a bone collar (Figure 6.4.2b). The bony edges of the developing structure prevent nutrients from diffusing into the center of the hyaline cartilage. This results in chondrocyte death and disintegration in the center of the structure. Without cartilage inhibiting blood vessel invasion, blood vessels penetrate the resulting spaces, not only enlarging the cavities but also carrying osteogenic cells with them, many of which will become osteoblasts. These enlarging spaces eventually combine to become the medullary cavity. Bone is now deposited within the structure creating the primary ossification center (Figure 6.4.2c ). Figure 6.4.2 – Endochondral Ossification: Endochondral ossification follows five steps. (a) Mesenchymal cells differentiate into chondrocytes that produce a cartilage model of the future bony skeleton. (b) Blood vessels on the edge of the cartilage model bring osteoblasts that deposit a bony collar. (c) Capillaries penetrate cartilage and deposit bone inside cartilage model, forming primary ossification center. (d) Cartilage and chondrocytes continue to grow at ends of the bone while medullary cavity expands and remodels. (e) Secondary ossification centers develop after birth. (f) Hyaline cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage.

62. Endochondral Ossification While these deep changes are occurring, chondrocytes and cartilage continue to grow at the ends of the structure (the future epiphyses), which increases the structure’s length at the same time bone is replacing cartilage in the diaphyses . This continued growth is accompanied by remodeling inside the medullary cavity (osteoclasts were also brought with invading blood vessels) and overall lengthening of the structure (Figure 6.4.2d). By the time the fetal skeleton is fully formed, cartilage remains at the epiphyses and at the joint surface as articular cartilage. After birth, this same sequence of events ( matrix mineralization, death of chondrocytes, invasion of blood vessels from the periosteum, and seeding with osteogenic cells that become osteoblasts ) occurs in the epiphyseal regions, and each of these centers of activity is referred to as a secondary ossification center (Figure 6.4.2e). Throughout childhood and adolescence, there remains a thin plate of hyaline cartilage between the diaphysis and epiphysis known as the growth or epiphyseal plate (Figure 6.4.2f). Eventually, this hyaline cartilage will be removed and replaced by bone to become the epiphyseal line. Figure 6.4.2 – Endochondral Ossification: Endochondral ossification follows five steps. (a) Mesenchymal cells differentiate into chondrocytes that produce a cartilage model of the future bony skeleton. (b) Blood vessels on the edge of the cartilage model bring osteoblasts that deposit a bony collar. (c) Capillaries penetrate cartilage and deposit bone inside cartilage model, forming primary ossification center. (d) Cartilage and chondrocytes continue to grow at ends of the bone while medullary cavity expands and remodels. (e) Secondary ossification centers develop after birth. (f) Hyaline cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage.

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