Human Skeletal System PDF

Human Skeletal System Skeletal System Bones, Cartilages, and Ligaments (sometimes) are tightly joined to form a strong, flexible, framework called the skeletal system Functions of Skeletal System Protects our vital internal organs Cranium/ Skull Brain Rib Cage Hea...

Human Skeletal System Skeletal System Bones, Cartilages, and Ligaments (sometimes) are tightly joined to form a strong, flexible, framework called the skeletal system Functions of Skeletal System Protects our vital internal organs Cranium/ Skull Brain Rib Cage Heart & Lungs Provides a framework for the movement of our body through our muscles Stores minerals that our body needs to function properly Produces blood cells (from bone marrow)  Bones Cartilages Rigid, tough and not flexible Flexible and Elastic Made up of Osteoblast, Made up of Chondrocytes Osteoclast, Osteocytes Chondrin protein Ostin protein Does not have a rich blood Have a rich blood supply supply Growth is bidirectional Growth is unidirectional CaCo3 and Ca3(PO4)2 Ca3(PO4)2 Skeletal System Axial Skeleton Axial Skeleton Consists of bones that lie Appendicular Skeleton around the longitudinal/ central axis Protects the vital organs Cranium: Brain; Ribs: Heart & Lungs; Vertebral Column: CNS 80 bones [Vertebra 26+ Ribs 24+ Sternum 1 + Skull 29] Appendicular Skeleton Helps in body movement Bones of lower and upper limbs 126 bones Upper limb (Hand) [30×2 = 60] Lower limb (Leg) [30×2 = 60] Pelvic: 2 Connecting bone Clavicle: 2 between Axial and Appendicular Skeleton Scapula: 2 (Pelvic) (Clavicle) (Scapula)  Axial Skeleton 80 bones [Vertebra 26+ Ribs 24+ Sternum 1 + Skull 29] Skull (29) 6 Auditory ossicles 1 Hyoid Bone Face (14) Cranium (8) Nasal (2) Frontal (1) Vomer (1) Ear Ossicles (6) Parietal (2) InferiorNasal Concha (2) Malleus (2) Incus (2) Hyoid (1) Occipital (1) Lacrimal (2) Temporal (2) Zygoma (2) Stapes (2) Sphenoid (1) Palatine (2) Ethmoid (1) Maxilla (2) Mandible (1)  Skull (28)= Paired Bones(22) + unpaired(6) Paired 1. Nasal 6. Parietal 2. Lacrimal 7. Temporal 3. Inferior Nasal 8. Palatine Concha 9. Malleus 4. Maxillary 10. Incus 5. Zygomatic 11. Stapes Vertebral Column (26) Vertebral Formula: C7T12L5S(5)C(4) Ribs (24) + Sternum (1) In humans there are normally 12 pairs of ribs The first seven pairs are attached directly to the sternum by costal cartilages and are called true ribs The 8th, 9th, and 10th pairs- false ribs-do not join the sternum directly but are connected to the 7th rib by cartilage Ribs (24) + Sternum (1) True Ribs attach directly to the sternum. False ribs attach through costal cartilage. Floating ribs have no attachment to the sternum. Characteristics of Sternum A partially T-shaped vertical bone that forms the anterior portion of the chest wall centrally The sternum is divided anatomically into three segments: manubrium, body, and xiphoid process The sternum connects the ribs via the costal cartilages forming the anterior rib cage Appendicular Skeleton (Upper Limb) Total: 30 1 Humerus 1 Radius (towards thumb) 1 Ulna (towards little finger) 8 Carpels 5 Meta carpels 14 Phalanges Appendicular Skeleton (Lower Limb) Total: 30 1 Femur 1 Tibia (most shining bone) 1 Fibula (thin bone) 1 Patella 7 Tarsals 5 Meta tarsals 14 Phalanges Appendicular Skeleton (Pelvic, Clavicle, Scapula) Pelvic: It is a basin like structure which connects the spine to lower limbs Clavicula (collar bone) is a fully developed rod-shaped bone in man but it becomes reduced in domestic mammals. The rudimentary clavicle is embedded in the muscle as a small ossicle (fe), a cartilage (ca) or a tendinous band (Un) Scapula is the main structure of shoulder girdle in domestic mammals. It is well- developed and carries the foreleg. It is connected to body by extrinsic scapular muscles The scapula is the most familiar wide flat, triangular bone. The shape of the bone likes a trowel or small shovel, so the name originates from in Greek word «skaptein-to dig» It placed on a cranio-lateral aspect of the thoracic cage with almost 60° to ground Characteristics of Bones Bone is the hardest tissue in the body and supports various organs The matrix is tough containing both inorganic and organic substances The inorganic salts present in the matrix are Calcium Phosphate, Calcium Carbonate, Calcium Fluoride, Magnesium Phosphate etc. If the bone is treated with Hydrochloric acid or EDTA for some time, its inorganic matter is dissolved and the organic matter is left behind Such a bone is called as decalcified bone Microscopic Structure of Human Bones The mammalian bone consists of the following parts: 1. Periosteum 2. Matrix 3. Endosteum 4. Bone Marrow Periosteum It is a thick and tough sheath that forms an envelop around the bone It comprises two distinct layers; Fibrous layer Osteogenic layer a thin outer layer of fibrous connective tissue and a layer of osteoblasts The Osteoblasts are called bone forming cells because they produce new bone material Matrix It is composed of a protein called Ossein The matrix forms thin plates called lamellae The lamellae which occur around the Haversian canals are called Haversian lamellae Circumferential or concentric lamellae are present inner to periosteum and outer to endosteum Osteocytes are present in lamellae Matrix Osteocytes are surrounded by a space called lacuna The lacunae lead into fine channels, the canaliculi containing protoplasmic processes of the osteocytes With the help of Canaliculi, one osteocyte is in contact with another A Haversian canal and its lamellae and osteocytes form a Haversian System (Osteon/ Basic functional unit of compact bone) Haversian systems are absent in Spongy bones Endosteum It is present outer to the bone marrow cavity Like the periosteum it comprises two distinct layers; a thin inner layer of fibrous connective tissue and a layer of osteoblasts which produce new bone material The growth of bones is bi- directional Bone Marrow In long bones such as Humerus and Femur, a cavity called bone marrow cavity is present inner to the endosteum The bone marrow cavity is filled with a soft and semisolid fatty neurovascular tissue termed as Bone Marrow Types of Bone Marrow 1. Red Bone Marrow It is red due to abundant blood vessels It is present in the epiphyses and produces RBCs, WBCs, and Platelets 2. Yellow Bone Marrow It is present in shafts of long bones It is yellow in colour and has much fatty tissues It produces blood cells in emergency Yellow bone marrow may be replaced by red bone marrow in anaemia Joints The structural arrangements of tissues by which bones are joined together are called joints Locomotion is the ability to move from one place to another The major key factors that help in locomotion are bones and muscles Bones allow movement through different types of joints Joints ❖ Joint (or articulation/ articular surface): the junction/ connection between two or more bones ❖ With the exception of Hyoid bone, every bone in the body is connected to or forms a joint ❖ There are 230 joints in the body ❖ The type and characteristics of a given joint determine its degree and type of movement ❖ Joints can be classified based on structure and function Classification of Joints There are two different types of joints- Structural and Functional classification of joints Structural Classification 3 types 1. Fibrous Joints/ Fixed/ immovable joints 2. Cartilaginous Joints/ Slightly movable joints 3. Synovial Joints/ Freely movable joints Fibrous Joints In this type of joints there is no movement between the bones concerned As the name suggests, there is white fibrous tissue between the ends of the bones Fixed joints, also called immovable joints, are found where bones are not flexible In such joints, bones have been fused together in such a way that they are fixed to that part, most commonly to create a structure A prominent example of a fixed joint is the skull, which is made up of a number of fused bones Other examples include the upper jaw, rib cage, backbone, and pelvic bone, etc. Cartilaginous Joints A pad of white fibrocartilage between the ends of the bones take part in joints They allow very slight movement Movement is only possible due to the compression of pad of cartilages Examples include the pubic symphysis of pubis and the joints between the vertebra (intervertebral discs) Synovial Joints A considerable movement is possible at all synovial joints The synovial joints are the most common type of joint because this joint helps us to perform a wide range of motion such as walking, running, typing and more Synovial joints are flexible, movable, can slide over one another, rotatable and so on These joints are found in our shoulder joint, neck joint, knee joint, wrist joint, etc. Structure of a Generalized Synovial Joint There is present a membrane called Synovial membrane This membrane is composed of secretory epithelial cells which secrete a thick sticky fluid, of the consistency of the white of an egg called Synovial fluid It acts as a lubricant to the joints, provides nutrient materials for the structures within the joint cavity and helps to maintain the stability of the joint, it prevents the ends of the bones from being separated Structure of a Generalized Synovial Joint Bone ends are covered by articular cartilages Ligaments join the bones and tendons connect the bones with muscles Little Scas of synovial fluid or bursae are found in some joints to provide cushion Functional Classification of Synovial joints Functional classification of joints is based on the type and degree of movement permitted Based on their shapes, and degree of movement permitted There are six types of freely movable joint 1. Gliding Joint 1. Hinge Joint 3. Pivotal Joint 4. Ellipsoid/ Condyloid Joint 5. Saddle Joint 6. Ball and Socket Joint 1. Gliding Joint Simplest type of Synovial joints The articular surfaces are usually flat Permit only back-and-forth and side- to-side movements No rotation or twisting is possible because the bones are packed closely together by ligaments Gliding joints are found between the carpal bones and between the tarsal bones 2. Hinge Joint Allows movement primarily in one plane In a hinge joint spool (reel) like surface of one bone fits into the concave surface of another bone The elbow, the knee, ankle and interphalangeal joints are examples of hinge joints 3. Pivotal Joint Allows movement in only one plane In a pivotal joint, rounded or pointed bone fits into a shallow depression in another bone The joints between atlas and axis and between the radius and ulna (radioulnal joint) are examples of pivotal joints The primary movement at a pivot joint is rotation 4. Ellipsoid/ Condyloid Joint Allows movement in two planes, back and forth and side-to-side An oval shaped condyle of one bone fits into an elliptical cavity in another bone The joints between the metacarpals and phalanges (metacarpo- phalangeal joint) of the fingers are examples of ellipsoid joints Metacarpo-phalangeal joint 5. Saddle Joint Allows the same movements as an ellipsoid joint, but the movements are free The projection of one bone fits in saddle-shaped depression in another bone The joint between the carpal and metacarpal of thumb (carpometacarpal joint of thumb) is an example of saddle joint 6. Ball and Socket Joint This is the most free movable of all joints In a ball and socket joint as the name suggests, a ball like structure of the bone fits into a socket like structure in another bone Shoulder and hip joints are the examples of ball and socket joint 6. Ball and Socket Joint Between the glenoid cavity of the pectoral girdle and the head of the humerus and between acetabulum of pelvic girdle and the head of the femur 1. Pivot Joint 2. Hinge Joint 3. Saddle Joint 4. Plane Joint 5. Ball and Socket Joint 6. Condyloid Joint 7. Ellipsoid joint