Anatomy and Physiology of the Skeletal System PDF

ANATOMY AND PHYSIOLOGY ○ Production of red blood cells THE SKELETAL SYSTEM that occur within the marrow ➔ Skeleton comes from a Greek word cavities of certain bones meaning dried up body ➔ Afte...

ANATOMY AND PHYSIOLOGY ○ Production of red blood cells THE SKELETAL SYSTEM that occur within the marrow ➔ Skeleton comes from a Greek word cavities of certain bones meaning dried up body ➔ After body decomposition, bones are A. BONES OF THE HUMAN BODY still intact because bones have Two basic types of bone tissue: mineral content of limestone 1. Compact Bone ➔ Bones appear dead and dried up – Dense/hard – provide structural Bone is living tissue support and movement (locomotion) ➔ Newborn human has 350 bones; Covered in the periosteum where bones are not yet fused together muscles and tendons attach ➔ Adult human has 206 bones 2. Spongy Bone ➔ Weighs about 30 pounds Cancellous – tissue on the “inside” of the bone Functions of the Bones: Made up of slender fibers and Support of the body (framework) lamellae and is filled with marrow ○ Concrete reinforcement of which creates red blood cells the body Adds flexibility and a level of shock Protection of soft organs absorption to the bone, and stores ○ Skull protecting the brain; minerals (99% of the body’s Spinal cord protects the calcium) spinal cavity; spinal vertebrae surrounds spinal structure ○ Rib cage protecting the vital organs of the thorax Serves as levers (with help from muscles) Allows movement ○ Muscles use bones as levers to move the body Osteon Storage of minerals and fats Functional units of compact bone (calcium) Cylindrically-shaped and connected ○ Fat stored in the internal together inside compact bone (marrow) cavities of bones Made of lamellae, lacunae, and ○ Most of the body’s calcium is osteocytes arranged around a central deposited in the bones as canal calcium salts; also stores ★ Clopton Havers - first to study phosphorus osteons in depth, published first Blood cell formation description of osteon in 1691 (hematopoiesis) Lamellae Singular: lamella Layers of matrix Extracellular matrix around cells that gives compact bone its hardness and rigidity Made of both organic and inorganic materials Collagen provides tensile strength Hydroxyapatite crystals provide compressive strength Canals 1. Haversian Canal Three types of Lamellae: Concentric lamellae 1. Interstitial Lamellae Arranged around the central canal Irregularly shaped 2. Central Canal Fill spaces between osteons Parallel to the long axis of the bone 2. Circumferential Lamellae Where blood vessels, lymph vessels, Wrap around circumference of the and nerves are located bone Contains small amount connective 3. Concentric Lamellae tissue Circular 3. Perforating Canal (Volkmann's Arranged concentrically around the Canal) central canal of each osteon Run at right angles to central canals Connects central canal’s blood vessels with the periosteum’s blood supply Lacunae Singular: Lacuna Gaps or empty spaces Lacunae within the lamellae contain osteocytes B. GROSS ANATOMY OF A BONE Red marrow is confined in cavities of spongy bones (hip bones and epiphysis of long bones) Epiphyseal Growth Plate Contains hyaline cartilage in a growing bone Once the bone stops growing, the cartilage is replaced by osseous tissue and the plate becomes a line Articular Cartilage Made also of hyaline cartilage Reduces friction and acts as a shock absorber Covers the external surface of the epiphyses Periosteum Outsides covering of the diaphysis Fibrous connective tissue membrane Diaphysis Serves as an attachment for muscles Shaft Contains blood vessels, nerves, and Walls are composed of dense and lymphatic vessels hard compact bones; for strength Tendons and ligaments attach to the Hollow region (medullary cavity) bone filled with yellow marrow Arteries Cavity is lined with endosteum Supply bone cells with nutrients (composed of delicate connective tissues) where bone growth, repair, C. CLASSIFICATION OF BONES and remodeling occur Epiphysis Ends of the bone Composed mostly of spongy bone (consists of red bone marrow) Structure of a Long Bone: Medullary Cavity Cavity of the shaft Contains yellow marrow (mostly fat) in adults Contains red marrow (for blood cell L.S.F.I.S formation) in infants; until age 7 Long Bones  Typically longer than wide diameter and in density through Have a shaft with heads at both ends exercise Contains mostly compact bone (for durability) D. GENERAL BONE MARKINGS Responsible for absorbing the stress Articulation of the body’s weight at several Area where two bones meet different points Example: right humerus and scapula Found in legs and arms (radius) Examples: femur, humerus Short Bones Generally cube-shaped and small (pea-sized) Contains mostly spongy bone Found in wrists, ankles, and toes Projection Examples: carpals, tarsals Area that projects above the surface Flat Bones of the bone Thin and flattened Example: left temporal bone Usually curved Covers organs and provides surface for large muscles Thin layers of compact bone around a layer of spongy bone Examples: skull, ribs, sternum Irregular Bones Hole Irregular shape Opening or groove in the bone that Does not fit into other bone allows blood vessels and nerves to classification categories enter Example: vertebrae, hip Example: sacrum Sesamoid Bones Embedded in tendons Most notable example is the patella (knee cap) Vary in number from person to person, and are typically only a few millimeters in size Process: Sesamoid came from the Latin word Head “sesamum” meaning “sesame seed” Round surface of a bone that helps form a joint ★ Bones stop growing in length during Example: right talus (found in puberty, but they can grow in tarsals)  Body Largest and main segment of the bone Example: left scaphoid, left calcaneus, body of sternum Facet Smooth and flat surface that help from gliding joint Example: thoracic vertebrae Body of sternum Epicondyle Rounded projection that sits on top of the condyle and allows connective tissues to connect to the bone Example: left humerus, left femur Condyle Provides structural support Absorbs most of the force exerted by the joint Example: left tibia Femur Crest Raised ridge projection that is part of the edge of a bone Allows connective tissues to connect to the bone Neck Examples: left ilium, left pubis, Narrowing of the bone where the frontal bone shaft of the long bone (diaphysis) meets the end of the long bone Example: right 1st rib, left radius Ilium Spine (Spinous Process) Left radius  More pronounced raised, sharp elevation of bone that allows connective tissues and muscles to connect to the bone Found in vertebrae Examples: T01 vertebra, L03 vertebra, right scapula Tubercle of mandible Foramen Round hole where blood vessels, nerves, or ligaments pass through Example: right zygomatic bone, sphenoid, occipital Vertebra Tuberosity Large projection on the side of the bone/ moderate projection that allows connective tissues to connect to the bone Examples: left femur, right 5th Meatus metatarsal, right ischium, left radius Tube-like channel that provides passage and protection to nerves and vessels within the bone Example: right temporal bone Ischial tuberosity Tubercle Small round projection that allows connective tissues to connect to the bone Example: C03 vertebra, mandible, Fissure left fifth rib Slit in the bone that usually houses nerves and blood vessels Example: right maxilla  E. CHANGES IN THE HUMAN SKELETON Sulcus In embryos, the skeleton is primarily Groove that accommodates a nerve, hyaline cartilage blood vessel, or tendon During development, much of this Example: right talus cartilage is replaced by bone; in the third trimester, some cartilage are already replaced by bones Cartilage remains in isolated areas: (parts important for motion and bending of fetus inside the womb ○ Bridge of the nose ○ Parts of ribs Fossa ○ Joints Shallow depression in a bone’s surface that allows other bones to F. BONE GROWTH articulate with it Epiphyseal plates allow for growth Example: left humerus of long bone during childhood ○ New cartilage is continuously formed ○ Older cartilage becomes ossified (turns to bone) ○ Cartilage is broken down ○ Bone replaces cartilage Hyaline cartilage leaves remnants of Sinus epiphyseal plates to form epiphyseal Cavity within an organ or tissue lines Example: ethmoid bone Bones are remodeled and lengthened until growth stops ○ Grows longitudinally for height ○ Grows in width to support weight (appositional growth)  Break down bone matrix for Bone Width remodeling and release Long after longitudinal bone growth (reabsorption) of calcium has stopped, bones continue to grow in thickness and width (in Bone Remodeling preparation for support, structure, Process by both osteoblasts and and proper posture) osteoclasts Bones are continuously being Osteoblasts deposit bone on the reshaped external bone surface (bricklayer) Osteoclasts break down bone from Epiphyseal Disc the inside Growth plate To retain normal proportions and Cartilage near the epiphyseal disc strength during long bone growth multiplies and eventually becomes (increase in body size and weight) ossified (turns to bone) In response to: As long as new cartilage continues to ○ Calcium ion in blood (more form, the bone continues to lengthen calcium ion in the blood, When the growth plate hardens and more bone growth) becomes ossified, growth stops ○ Pull of gravity and muscle on Hormone play a big part in this the skeleton ○ Growth hormones stimulates growth H. Long Bone Formation and Growth ○ Sex hormones stop growth (during puberty) ★ Your skeleton is replaced every 10 years G. TYPES OF BONE CELLS Osteocytes Mature bone cells Osteocytes have access to blood vessels and provide the bone with nutrients I. BONE FRACTURES Osteoblasts A break in a bone Bone-forming cells (secreting Types of bone fractures: extracellular matrix) Closed (Simple) Fracture – break Osteoclasts that does not penetrate the skin; Bone-destroying cells allows for bone regeneration  Open (Compound) Fracture – broken bone penetrates through the skin; needs surgery Bone fractures are treated by reduction and immobilization ○ Realignment of the bone Common Types of Fractures: Impacted Comminuted Broken bone ends are forced into Bone breaks into three or more each other fragments Commonly occurs when someone Fixed by putting plates attempts to break a fall with Common in older people who have outstretched arms more brittle bones Spiral Compression Ragged break occurs when twisting Bone is crushed forces are applied to a bone Common in porous bones (ex: Common sports fracture osteoporotic bones of older people) Depressed Greenstick Broken bone portion is pressed Bone breaks incompletely, much in a inward green twig breaks Typical in skull fractures Requires surgery Common in children, whose bones are more flexible than those of adults Dislocation of a Joint Displacement of bones at the joint  ○ Often caused by impact ○ Axial Skeleton trauma to that joint Bones of the cranium, Can be more damaging and painful face, vertebral than a fracture column, and bony ○ Damage to the joint capsule thorax and surrounding ligaments ○ Appendicular Skeleton and tendons often take much Bones of the pelvic longer to heal than bone girdles, the upper tissue extremities and lower extremities Repair of Bone Fractures 1. Hematoma (blood-filled swelling) is formed Bruising Bone cells are deprived of nutrition 2. Break is splinted by fibrocartilage to form a soft callus Blood vessels grow into the hematoma 3. Fibrocartilage callus is replaced by a bony callus K. THE AXIAL SKELETON Slowly becomes spongy bone Forms the longitudinal part of the 4. Bony callus is remodeled to form a body permanent patch Divided into parts: Response to mechanical stress ○ Skull ○ Laryngeal skeleton Hematoma -> Fibrocartilage -> Bony Callus ○ Vertebral column (S-shaped) ○ Bony thorax (part of the ribs, Stages in the Healing of a Bone Fracture sternum, and vertebrae) L. THE SKULL Sits on top of the vertebral column Two sets of bones ○ Cranium (8 bones) ○ Facial bones (14 bones) Bones are joined by sutures Only the mandible (part of facial J. DIVISIONS OF THE SKELETAL bone) is attached by a freely movable SYSTEM joint (temporomandibular joint) Divided into two divisions:  Not part of the facial skeleton; part of the calvaria Frontal bone articulates with 12 other bones (10 of 12 belongs to the facial skeleton) Parietal Bone (2) Upper sides of the head and the roof of the cranial cavity (top of the head) Temporal Bone (2) M. CRANIAL BONES Sides of the head, close to ears The Cranium Commonly called the temples Includes the external auditory meatus Bony structure that encases and (opening for the ear) protects the brain Includes the zygomatic process (part Calvaria (skull cap) is the upper part of the cheekbone) (connected to the of the cranium maxillary bone) Each bone in the calvaria is named Styloid process - pointed projections for corresponding lobe of the at the bottom; where muscles of neck cerebrum — the largest part of the and tongue is attached brain Occipital Bone (1) ○ Frontal bone protects the Back and base of the cranium frontal lobe Protects the occipital lobe ○ Parietal bones protect the Gives passage to the medulla parietal lobes oblongata, which connects the brain ○ Occipital bone protects the to the spinal cord occipital lobe Includes the foramen magnum ○ Temporal bones protect the (foramen = hole) temporal lobes ○ Large hole for the brainstem and spinal cord to connect Sphenoid Bone (1) Forms sides of cranium and parts of orbits of the eyes Butterfly-shaped ○ Includes sella turcica (Turk’s saddle) ○ Where the pituitary gland sits Sphenoid and ethmoid are not part of Bones of the Cranium: the calvaria but part of the cranium Frontal Bone (1) Bat-shaped bone and is the keystone Gives shape to the forehead, orbits, bone at the base of the cranium and nasal cavity Ethmoid Bone (1) Horseshoe-shaped mandible is the Irregularly-shaped bone located largest and strongest of the facial between the eye orbits bones Spongy, cubed bone that gives shape Carries the lower teeth to part of the roof of the nose and the Anterior portion forms the chin orbits Only freely movable joint in the The ethmoid is also home to skull numerous foramina through which Articulates with the temporal bones the branches of the olfactory nerves at the temporomandibular joint (smell) pass The cribriform plate of the ethmoid supports the olfactory bulb (the terminus of the olfactory bulb) Suture Fibrous joint found only in the skull Maxilla (2) Parietal bones come together to form Upper jaw the sagittal suture and also form the Forms the upper jaw and the coronal suture with the frontal bone boundary of three cavities: ○ Roof of the mouth ○ Floor and lateral wall of the nasal cavity ○ Floors of the orbits Palatine Bones (2) N. THE FACIAL SKELETON Form the posterior part of the hard Facial Bones: palate and the floor of the nasal 14 bones cavity Most of these bones come in pair Posterior borders of the palatines Only mandible and vomer are single serve as the attachment site of the bones soft palate, and the sharp medial Mandible (1) borders form the posterior nasal Lower jaw bone spine for the attachment of the uvula  ★ Failure of the palatine and/or maxillary bones to fuse causes a cleft palate Vomer Nasal septum Superior half of the vomer is fused with the perpendicular plate of the Zygomatic Bone (2) ethmoid, and its lower half attaches The cheekbones to the septal cartilage Also forms a part of the orbits of the Posterior border is free and separates eyes the choanae, also known as the Connected to the temporal bone internal nares ★ People with high cheekbones simply have zygomatic bones that project outward more Inferior Nasal Conchae (2) Nasal conchae consist of a layer of spongy bone curled up on itself like a scroll Nasal (2) and Lacrimal Bones (2) Medial surface of the conchae are Inner wall of eye sockets perforated for the passage of Make up the bridge of the nose and numerous vessels attach to the nasal cartilage Folds of the conchae increase the The lacrimal bones (inside the orbits) surface area of the nasal cavities. contain the lacrimal sacs that Enhances warming and humidifying continue as the nasolacrimal ducts, air passing over them or tear ducts Smallest bones to make up the facial bones O. PARANASAL SINUSES Q. THE HYOID BONE Air filled cavities U-shaped Functions of paranasal sinuses: Found in the upper neck ○ Lighten the skull Only bone that does not articulate ○ Give resonance and with another bone; somehow floating amplification to the voice Serves as a moveable base for the tongue P. THE FETAL SKULL Large compared to the infants total Middle Ear body length 3 tiny bones that transmit vibrations Fontanelles - fibrous membranes All derived from Latin words connecting the cranial bones ○ Malleus (Hammer) ○ Allow the brain to grow ○ Incus (Anvil) ○ Convert to bone within 24 ○ Stapes (Stirrup) months after birth Smallest and lightest bone All three bones are laid end to end are only one inch long R. THE VERTEBRAL COLUMN Backbone or spine Consists of 26 bones called vertebrae ★ You shrink ¼ during the day (vertebral discs compress and  dehydrate) but you gain it back when Atlas and Axis you sleep Atlas is the topmost vertebra, sitting just below the skull. The axis is Atlas and Axis below it The atlas (topmost) and axis are part These support the skull, facilitate of the seven cervical vertebrae head and neck movement, and These vertebrae have a few unique protect the spinal cord features: They form only the craniovertebral ○ Smallest of the vertebrae joints in the human body ○ C01-C06 have three ○ Craniovertebral joint permits foramina: (one vertebral and movement between cervical two transverse) vertebrae and neurocranium ○ Protrusion that can be felt at Gives passage to its dorsal and the back of the neck is the ventral roots non-bifid spinous process of C07 Atlanto-Occipital Joint Connects atlas to occipital bone Flexes the neck, allowing you to nod your head Atlas (C01) Ring-like and consists of an anterior and posterior arch, and two lateral masses Holes on the processes, or foramina, Atlanto-Axial Joint give passage to the vertebral artery Connects axis to the atlas and vertebral vein Permits rotational movement of the Connected on the base part of the head occipital bone Axis (C02) C1-C7: neck region (7 cervical Has a spinous process that is not vertebrae) obviously bifid like the rest of the T1-T12: chest region (12 thoracic cervical vertebrae vertebrae) The dens rises perpendicular from L1-L5: lower back (5 lumbar the upper surface of the axis body. It vertebrae) articulates with the ring formed by Sacrum: curved bone of the lower the anterior arch and the transverse back (posterior wall of the pelvis) ligament of the atlas, creating the ○ Fused sacral vertebrae pivot joint ○ 5 vertebrae at birth The spinous process serves as the ○ Came from the Latin word attachment site for many muscles of “os sacrum” or “sacred the spine, as well as the nuchal bone” ligament ○ Considered sacred because it was often part of an animal that was offered in sacrifice ○ Has holes that allow passageway of vessels and nerves ○ In the female skeleton, the sacrum is shorter and wider ★ Lower parts of the vertebrae are than in the male, it is directed bigger because they are needed for more obliquely backward, support and structural function increasing the size of the pelvic cavity Lumbar Vertebrae Coccyx: tailbone ○ 4 vertebrae at birth ○ Terminal portion of the vertebral column and forms part of the posterior wall of the pelvic cavity ○ Resembles a miniature sacrum in shape Vertebral foramen The Vertebral Column ○ Opening for spinal cord Vertebrae separated by intervertebral discs (acts as shock absorbers) Spine has a normal curvature Each vertebrae is given a name according to its location S. BONY THORAX (THORACIC CAGE) A. APPENDICULAR SKELETON Chest region Consists of 126 bones Forms a cage to protect major organs Limbs (appendages) Composed of sternum, ribs, and Pectoral girdle (shoulder) thoracic vertebrae Pelvic girdle Sternum ○ Breastbone B. BONES OF THE SHOULDER ○ Dagger-shaped bone located GIRDLE along the midline of the Composed of two bones: anterior chest Clavicle - “collarbone” Ribs Scapula - “shoulder blade” ○ 12 pairs attach posteriorly to These bones allow the upper limb to the thoracic vertebrae have exceptionally free movement ○ True ribs (first 7 pair) – because of the following factors: connected directly to sternum ○ Each shoulder girdle attaches ○ False ribs (last 5 pairs) – to the axial skeleton at only connected only by cartilage one point, the ○ Floating ribs (not connected) sternoclavicular joint ○ The loose attachment of the scapula allows it to slide back and forth against the thorax as muscles act ○ The glenoid cavity is shallow, and the shoulder  joint is poorly reinforced by Sometimes called the “wing” ligaments because they flare when we move ★ Collarbone is the most commonly our arms posteriorly broken bone among children. Each scapula has a flattened body Usually occurs by falling on an with three borders: superior, medial, outstretched arm lateral Acromion Clavicle ○ Where lateral end of the Slender bone that connects parts of clavicle is connected to the anterior thorax ○ enlarge lateral end of the Acts as a brace to hold the arm away spine from the top of the thorax and Acromioclavicular Joint prevent shoulder dislocation ○ Where acromion connects Medial (sternal end) – connected to with the clavicle laterally the manubrium (head of the Glenoid Cavity sternum) ○ Shallow socket that receives Clavicular notch – where medial the head of the humerus end of the clavicle sits on Suprascapular Notch Lateral (acromial end) directly ○ Where nerves pass through connected to the acromion; Superior Angle and Subscapular connected by acromioclavicular Fossa joint ○ Where muscles of the chest are inserted to 2 processes: ○ Acromion enlarge lateral end of the spine of the scapula ○ Coracoid Process “Beaklike” Points laterally over the top of the shoulder Scapula Anchors some Glenoid cavity muscles of the arms Shallow socket that receives the head of the humerus Shoulder joint is poorly reinforced by ligaments  ○ Runs obliquely down the posterior aspect of the shaft ○ Where radial nerve passes on The Forearm Ulna The longer of the forearm bones Located on the medial or little finger side of the forearm C. BONES OF THE UPPER LIMB ○ Olecranon Process – consists The Arm of the bone of the proximal Formed by a single bone, humerus ulna from the base of the Humerus coronoid process proximally Head of humerus allows for rotation Radius 2 Tubercles of the Humerus: Located on the lateral or thumb side Greater tubercle of the humerus when the palm of the hand is facing Lesser tubercle of the humerus forward The head of the radius forms a joint Parts of the Humerus: with the capitulum of the humerus Anatomical Neck ○ Styloid Process – articulated ○ Slight constriction on the wrist immediately inferior to the ○ Radial Tuberosity – head articulated near the proximal Surgical Neck (the line) radioulnar joint; where ○ Common site of fracture or tendons of the bicep muscles breakage of the humerus attaches Deltoid Tuberosity Radioulnar Joint ○ Just below the surgical neck ○ Where both proximally and ○ Where deltoid muscles are distally the radius and ulna attached articulate ○ Deltoid muscle – largest arm Interosseous Membrane muscle; site of intramuscular ○ Connects the two bones injection Capitulum & Trochlea ★ Arms are among the most commonly broken bones, accounting for almost ○ Parts that are being connected half of all adults’ broken bones to the forearm Coronoid Process ○ Has a depression wherein the part of the ulna is connected Radial Groove  D. BONES OF THE PELVIC GIRDLE Composed of two coxal bones (hip bones) Composed of three pairs of fused bones ○ Ilium ○ Ischium ○ Pubis Total weight of the upper body rests on the pelvis Protects several organs: ○ Reproductive organs ○ Urinary bladder The Hand ○ Part of the large intestine Carpals (8) – wrist Pelvic Girdle – coxal bones and ○ Scaphoid Bone – one of the sacrum biggest bones in the carpal Pelvis – coxal bones, sacrum, and ○ Lunate coccyx ○ Triquetral Ilium ○ Pisiform - smallest bone in Connect posteriorly with the sacrum the carpal Large flaring bone that forms most ○ Trapezium of the hip bone ○ Trapezoid Alae – wing-like portion of the ilium ○ Capitate Sacroiliac Joint – joins the ilium ○ Hamate and part of the sacrum Metacarpals (5) – palm Ischium Phalanges (14) – fingers Sit down bone ○ Distal – thumb does not have Ischial Tuberosity – receives body a median phalange weight when in a sitting position ○ Middle Ischial Spine – superior to the ○ Proximal tuberosity Narrows the outlet of the pelvis Pubis Most anterior and inferior part Forms in the fusion of rami of the pubis Obturator Foramen – opening that allows blood vessels and nerves to pass into the anterior part of the thigh  Pubic Symphysis – pubic bones of Gender Differences of the Pelvis each hip articulate anterior to form a cartilaginous joint ★ During birth, the baby passes through the pelvic brim E. THE PELVIS Acetabulum Deep socket formed by the fusion of Female inlet is larger and more ilium, ischium, and pubis circular Accommodates the head of the Female pelvis is shallower femur Bones are lighter and thinner False Pelvis Female ilia flares more laterally Superior to the true pelvis Female sacrum is shorter and less Area medial to the flaring portions of curved the ilia Female ischial spine are shorter and True Pelvis farther apart (bigger outlet) Surrounded by bone Female pubic arch is more rounded Lies inferior to the flaring parts of the ilia and the pelvic brim F. BONES OF THE LOWER LIMB Outlet The Thigh Inferior opening of the pelvis Femur measured between the ischial spines Thigh bone Inlet Longest, heaviest, and strongest bone Superior opening between the right of the human body and left sides of the pelvic brim Its proximal end has a ball-liked head, a neck, and a greater trochanter and lesser trochanter, separated anteriorly by the intertrochanteric line and posteriorly by the intertrochanteric crest Lateral and Medial Condyle ○ Distal on the femur ○ Articulate with the tibia ○ Separated by the intercondylar fossa Patella ○ Kneecap  ○ Triangular bone located within a tendon that passes over the knee ○ Protects the anterior articular surface of the knee joint ○ Patellar surface – anteriorly on the distal femur; forms a joint with the patella The Foot Tarsal (7) – ankle ○ Body weight is carried mostly by the calcaneus and talus ○ Calcaneus – heel bone; largest tarsal The Leg ○ Talus – second largest tarsal; Tibia lies superior to the calcaneus Shin bone; larger Metatarsals (5) – sole/instep Tibial Tuberosity Phalanges (14) – toes ○ Roughened area on the anterior tibial surface Medial Malleolus ○ Forms inner bulge of the ankle Anterior Border ○ Unprotected by muscles which makes it easily felt beneath the skin Fibula Long and thin Lateral Malleolus ○ Distal end ○ Forms out part of the ankle G. JOINTS Articulation of bones Functions of joints include: ○ Holds bones together ○ Provide flexibility Ways joints are classified: ○ By their function ○ By their structure H. FUNCTIONAL CLASSIFICATION OF JOINTS Synovial Joints Synarthroses Articulating bones are separated by a ○ Immovable joints joint cavity Amphiarthroses Synovial fluid – found in the joint ○ Slightly moveable joints cavity Diarthroses Reinforced by ligaments ○ Freely moveable joints All joints in the limbs are synovial Fibrous Joints joints ○ Generally immovable Bursae – small fluid-filled sacs that Cartilaginous Joints reduce friction between moving parts ○ Immovable or slightly in your body’s joints moveable 4 distinct features: Synovial Joints Articular Cartilage ○ Freely moveable ○ Covers the ends of the bones forming the joints Fibrous Joints (Synarthrosis) Articular capsule Bones united by fibrous tissues – ○ Joint surfaces are enclosed by largely immovable a sleeve of fibrous connective Examples: sutures of the skull tissue lined with a smooth synovial membrane Joint Cavity ○ Articular capsule encloses a cavity called the joint cavity which contains a lubricating synovial fluid Reinforcing Ligaments ○ Fibrous layer of the capsule Cartilaginous Joints (Amphiarthrosis) is usually reinforced with Bones connected by cartilage ligaments Examples: pubic symphysis and intervertebral joints  ○ Ex: head (side to side “no” action), forearm joints (palm supination/pronation) 6 Types of Synovial Joints: H.B.P.S.G.C Hinge Joint ○ Like two beards joined Saddle Joint together by a hinge ○ When the surfaces of both ○ Movement in one direction articulation bones are ○ Ex: elbow, knees, fingers saddle-shaped ○ Concave/convex ○ Wide range of motion ○ Ex: thumbs Ball and Socket Joint ○ Ball-shaped end of one bone fits into the cup-shaped socket of another Gliding Joint ○ Bones can move in many ○ Interaction of flat surfaces of directions articulating bones ○ Ex: shoulder, hip ○ Limited but complex movement ○ Ex: wrist, ankle Pivot Joint ○ Allows for rotation around the length of a bone ○ Only for rotation  Condyloid Joint Causes pain and swelling in the ○ Oval-shaped articular surface joints of one bone fits into the oval-shaped depression of another THE MUSCULAR SYSTEM ○ Ex: mandible, knuckles Muscle ➔ Latin word “mus” – “little mouse” A. FUNCTIONS OF THE MUSCULAR SYSTEM Producing Movement ○ Contraction of skeletal muscle ○ Respond to change in I. INFLAMMATORY CONDITIONS external environment ASSOCIATED WITH JOINTS ○ Express emotion (smile and Bursitis frown) Inflammation caused by a bursa Maintaining Posture and Body usually caused by a blow or friction Position Tendonitis ○ Muscle adjust after the other Inflammation of tendon sheaths – maintain posture Arthritis Stabilizing Joints Inflammatory or degenerative ○ Skeletal muscle pulls on bone diseases of joints ○ Muscle tendon reinforces and Over 100 types stabilizes joints Most widespread crippling disease in Generate Heat the United States ○ Body heat – product of muscle activity (ATP) Clinical Forms of Arthritis: ○ Heat maintain normal body Osteoarthritis temperature Most common chronic arthritis Probably related to normal aging ❖ Like nervous tissue, muscles are processes excitable or “irritable” Rheumatoid Arthritis Has the ability to respond to Autoimmune disease – immune stimulus system attacks the joints ❖ Unlike nerves, muscles are also: Symptoms begin with bilateral Contractible (shorten) inflammation of certain joints Extensible (stretch) Often leads to deformities Elastic (return to original Gouty Arthritis shape) B. THREE TYPES OF MUSCULAR Cardiac Muscle TISSUE Pumping function of the heart Skeletal Muscle Cushioned by small amount Fibers are huge, of soft connective tissues cigar-shaped, multinucleate (endomysium) (many nuclei) Arranged in spiral or figure Located in the skeleton 8-shaped bundles Functions for movement, Striated, one central nucleus heat, posture Contract at a fairly steady Has striated, multinucleated rate (pacemaker) (eccentric), fibers parallel Involuntary Voluntary Smooth Muscle C. SKELETAL MUSCLE FIBERS Spindle-shaped Skeletal muscle is the only organ of Surrounded by scant the muscular system (sufficient) endomysium ○ Largest – 30 cm (1 ft in Contraction is slow and length) sustained ○ Forms contour of the body Peristalsis, blood pressure, Skeletal muscle is composed of pupil size, erects hairs skeletal muscle tissue and also No striations, one central contains nervous tissue (impulses), nucleus blood vessels, and connective tissue Found in hollow visceral Half of the body’s weight is muscle organs (digestive and urinary tissue tract) ○ Skeletal muscle = 40% in Involuntary males, 32% in females ○ Cardiac muscle = 10% Allows for movement, facial expressions, breathing, swallowing, writing, talking and singing, posture, heat production, joint stability  Tough overcoat of connective tissue that binds fascicle Aponeurosis Epimysia blends into a strong, cord-like tendon which attach muscle indirectly into bones, cartilages, or Connective Tissue Coverings connective tissue coverings Fascia Tendons Found after the hypodermis Tough collagenic fibers – anchors Surrounds an individual skeletal (holds on) to bone muscle, separating it from other muscles E. SKELETAL MUSCLE May extend beyond the ends of the ARRANGEMENT muscle to become a tendon Muscle fiber – single muscle cell May connect muscle to muscle and is ○ Fibers are made up of called aponeurosis myofibrils ○ Myofibrils are made up of D. ORGANIZATION OF MUSCLE thick and thin filaments TISSUE Sarcolemma – muscle cell Many large muscle groups are membrane encased in both a superficial and a Sarcoplasm – muscle cell cytoplasm deep fascia Myofibrils are striated ○ Striations are due to arrangement of thick and thin filaments ○ Seen as alternating areas of light and dark bands Sarcomeres – The length of each myofibril that is divided into repeating units Endomysium ○ Functional unit of skeletal Connective tissue sheath that muscle encloses a muscle fiber (cell) Perimysium Coarse fibrous membrane that wrap several sheath muscle fibers Outside layer of endomysium Fascicle Bundle of fibers Epimysium “Epi” – upon, over; “mys” – muscle F. STRUCTURE AND bands of adjacent myofibrils are ORGANIZATIONAL LEVELS OF aligned SKELETAL MUSCLE Sarcomere (segment of a myofibril) Muscle (organ) Contractile unit, composed of Consists of hundreds to thousands of myofilaments made up of contractile muscle cells, plus connective tissue protein wrappings, blood vessels, and nerve fibers Covered externally by epimysium Myofilaments or Filaments (extended Fascicle (a portion of the muscle) macromolecular structure) Discrete bundle of muscle cells, Thick filaments segregated from the rest of the ○ Contain protrusion of muscle by a connective tissue sheath bundled myosin molecules Surrounded by the perimysium Thin filaments Muscle Fiber (cell) ○ Contain actin molecules Elongated multinucleated cell (plus other proteins) It has a striated appearance Sliding of the thin filaments past the Surrounded by endomysium thick filaments produces muscle shortening Elastic filaments maintain the organization of the A band and provide elastic recoil when muscle contraction ends G. SARCOMERE ARRANGEMENT Myofibril or Fibril (complex organelles Alternating light (I) and dark (A) bands composed of bundles of myofilaments) Give muscle cell its striped Rodlike contractile elements that appearance occupy most of the muscle cell The banding pattern reveals the volume working structure of the myofibrils Composed of sarcomeres arranged Thick filaments end to end, they appear banded, and Myosin filaments Thin filaments ○ This is called Contractile protein “actin” troponin-tropomyosin Myosin complex Protein molecule ATPase enzyme – general power of contraction H. SARCOMERE STRUCTURE Sarcomere exists from Z-line to Z-line A-band is dark middle band ○ Overlapping thick and thin filaments K. PHYSIOLOGY OF SKELETAL I-band – thin filaments only MUSCLE CONTRACTION: Z-line – middle of the I-band NEUROTRANSMITTER RELEASE Myosin filaments are held to the Motor impulse is initiated in the Z-line by titin proteins brain (cannot act independently) Travels through the brain and spinal I. THICK FILAMENT STRUCTURE cord to a motor nerve ending Composed of many myosin Motor nerve endings (axons) molecules depolarize ○ Each myosin molecule has a Calcium enters the axonal endings tail region and 2 globular Calcium causes the release of heads (cross bridges) acetylcholine into the neuromuscular When they link, it junction (synaptic cleft) causes contraction J. THIN FILAMENT STRUCTURE Composed of actin protein ○ 2 strands of globular actin molecules twisted into a helix ○ Actin filaments have binding sites for myosin cross bridges ○ Tropomyosin protein spirals around actin helix Troponin protein (3 subunits) is attached to actin and holds tropomyosin in place Motor Neuron Stimulates contraction Nerve cell that innervates skeletal Calcium is important in the muscle tissue conduction of impulses to muscles Dendrites Receives information Axon Transmits information Has vesicles containing neurotransmitter that will stimulate or inhibit muscle contraction Neuromuscular Junction Site where branch of motor neuron(motor nerve ending) comes in contact with sarcolemma of Skeletal Muscle Contraction skeletal muscle fiber When a nerve impulse reaches a neuromuscular junction, acetylcholine (ACh) is released, upon binding to sarcolemma receptors, ACh causes a change in sarcolemma permeability leading to a change in membrane potential Steps: 1. Action potential arrives at axon terminal of motor neuron 2. Voltage-gated Ca2+ channels open. Motor End-Plate Ca2+ enters the axon terminal Sarcolemma of muscle fiber directly moving down its electrochemical beneath motor nerve ending gradient Contains an abundance of 3. Ca2+ entry causes ACh to mitochondria and nuclei neurotransmitters to be released by Chemical substance released from exocytosis vesicles in the motor nerve ending 4. ACh diffuses across the synaptic (axonal ending) cleft and binds to its receptors on the Acetylcholine (ACh) is the sarcolemma neurotransmitter released by motor 5. ACh binding opens ion channels in neurons the receptors that allow simultaneous When stimulated by a nerve impulse, passage of Na+ into the muscle fiber acetylcholine is released, travels and K+ out of the muscle fiber. More across the synaptic cleft and binds Na+ ions enter than K+ ions exit, receptors on motor end plate  which produces a local change in the Sliding Filament Mechanism end plate potential The sliding of actin on myosin (thin 6. ACh effects are terminated by its filaments on thick filaments) can be breakdown in the synaptic cleft by broken down into a 4-step process acetylcholinesterase and diffusion away from the junction With exposure of the myosin binding sites actin (thin filaments) – in the presence of Ca2+ and ATP – thick and thin filaments slide on one L. SLIDING FILAMENT THEORY another and the sarcomere is Sarcomere is the functional unit of shortened the skeletal muscle When a skeletal muscle contracts, sarcomeres shorten The sliding filament model of contraction states that during contraction, the thin filaments slides past the thick ones so that the actin and myosin filaments overlap to a M. PHYSIOLOGY OF SKELETAL greater degree MUSCLE CONTRACTION: POWER Thin filaments move towards the STROKE center of the sarcomere from both Calcium binds troponin (which is ends attached to tropomyosin) Moves tropomyosin from the myosin binding sites on actin Myosin cross bridges (heads) bind to actin  ○ ATP hydrolysis supplies Na & K needs to be normal level to energy prevent abnormal ability Actin is pulled inward towards the center of the sarcomere = POWER STROKE Sarcomere shorten as muscle contracts 1. ATP Hydrolysis 2. Attachment 3. Power Stroke 4. Detachment - muscle relaxes/depolarizes Muscle Relaxation Mechanism Acetylcholinesterase present in the NMJ destroys ACh (preventing continual stimulation) Calcium ions are transported from the sarcoplasm back into the SR N. PHYSIOLOGY OF SKELETAL Linkages between myosin and actin MUSCLE CONTRACTION: are broken; requires ATP bonding DEPOLARIZATION Then, the muscle fiber relaxes After ACh binds to the ACh receptors, its effects are quickly Energy for Contraction terminated by acetylcholinesterase, Muscle cells require huge amounts an enzyme located in the synaptic of ATP energy to power contraction cleft The cells have only a very small Acetylcholinesterase breaks down store of ATP ACh to its building blocks, acetic Three pathways supply ATP to acid and choline power muscle contraction: This removal of ACh prevents continued (and most likely undesirable) muscle fiber contraction in the absence of additional nervous system stimulation K-contractility happens outside of the cell  ATP is initially supplied from Exercise and Contraction cellular respiration In intense strenuous activity, oxygen If ATP is abundant, it is converted to can be depleted creatine phosphate and stored in Why? skeletal muscles ○ Contraction of skeletal When ATP is low, creatine phosphate muscles decreases blood supplies phosphate to ADP making delivery to muscles, nutrients ATP and O2 levels in contracting CP & ATP stores only good for muscles decrease about a 10 second maximal contraction ATP must then come from cellular respiration or glycolysis (in liver) Exercise and Skeletal Muscles Intense, strenuous exercise Oxygen & Muscle Contraction Muscles exceed capacity of Myoglobin of muscle (similar to respiratory and cardiovascular hemoglobin) binds to and stores systems to deliver oxygen for oxygen contraction Supplies O2 needed to make ATP for ATP supplied anaerobically through contraction glycolysis Pyruvate is converted to lactic acid Exercise and Skeletal Muscles Lactic acid builds up in muscles Prolonged, moderate exercise Causes muscles to fatigue ATP supplied through cellular respiration Oxygen Debt Once glycogen stores are depleted in Amount of oxygen needed by liver the muscle, glucose and fatty acid cells to use the accumulated lactic deliveries from blood are used as acid to produce glucose fuel source ○ Oxygen not available ○ Glycolysis continues ○ Pyruvic acid converted to lactic acid  ○ Liver converts lactic acid to Muscles provide applied force (AF) glucose required to overcome resistance Also the amount of oxygen needed to (load) (R) replace O2 levels in skeletal muscles Effort x length of effort arm = load x to pre-exercise levels length of load arm Force x distance = resistance x distance Functions are to change: ➔ Direction of an AF (applied force) ➔ Distance & speed of movement produced by an AF ➔ Effective strength of an AF Three Classes: Depend on the relationship between Heat Production applied force, fulcrum, and Cellular respiration is only about resistance 40% efficient First Class About 60% of the energy found in a ○ LOAD-FULCRUM- glucose is lost as heat during cellular EFFORT respiration ○ Ex: scissors Muscle contraction generates heat ○ In the body, when you raise because muscles use large amounts your head off your chest of nutrients to make ATP, generating ○ Load = facial skeleton large amounts of heat ○ Fulcrum = atlanto-occipital Heat is used to maintain body joint temperature ○ Effort = posterior neck muscles (pull) O. LEVER SYSTEMS: BONE-MUSCLE RELATIONSHIPS The operation of most skeletal muscles involves leverage – using a lever to move some object Lever – rigid bar that move on Second Class Fulcrum – fixed point ○ FULCRUM-LOAD- Force/Effort – used to move a EFFORT resistance or load ○ Ex: wheelbarrow Joints – acts as fulcrums ○ In the body, when you stand Bones – acts as levers on tiptoe  ○ Fulcrum = joints of the ball ★ Origin and insertion provide useful of the foot points of reference. Understanding ○ Load = weight of the body functional relationships of these ○ Effort = calf muscles pulling point during muscle contraction upward on heel helps in deducing muscle actions Q. BASIC BODY MOVEMENTS Flexion Decrease the angle of the joint Brings two bones together Hinge joint - bending Extension Third Class Increase the angle or distance ○ LOAD-EFFORT- between bones FULCRUM Abduction ○ Ex: tweezer Moving limb away from the midline ○ In the body, when flexing the Fingers and toes spread apart forearm by the biceps brachii Adduction ○ Load = hand and distal end Moving limb toward the midline of the forearm Rotation ○ Effort = proximal of the Movement of bone around forearm longitudinal axis ○ Fulcrum = elbow joint Ex: ball and socket joint, movement of atlas around the dens Circumduction Combination of flexion, extension, abduction, and adduction Ex: ball and socket joint (shoulder) Proximal end is stationary and its P. MUSCLE ATTACHMENTS distal end is moving in circle Point of Attachments: Origin Point of attachment does not move (immovable) More stationary at a joint when contraction occurs Insertion Moves during contraction Inserted bone towards the origin bone Inversion R. INTERACTION OF SKELETAL Turns the sole medially (inward) MUSCLE IN THE BODY Eversion ➔ Muscle groups produce an opposite Turns the sole laterally (outward) movement on the opposite side of Dorsiflexion joint Lifting foot ➔ Produces smooth and coordinated Superior surface approaches shin movements Walking on heels Prime Movers/Agonists Plantar Flexion Causing a particular movement Depressing the foot Antagonists Pointing the toes Oppose or reverse the movement Flexion of the hands Stretched and relaxed when prime Supination mover is active Turning forward Synergist Palms face anteriorly Helps prime mover by producing the Pronation same movement or by reducing Turning backward movement Palms face posteriorly Ex: finger flexor muscle of both Opposition wrist and the finger joint Saddle joint between the metacarpal Fixator 1 and the carpal Specializes synergist Maintains the position Stabilizes the origin of a prime mover so all the tension can be used to move the insertion bone S. NAMES OF SKELETAL MUSCLE 1. Direction of the Muscle Fiber ➔ Reference to imaginary line (midline or long axis) Rectus ○ Straight ○ Muscle fiber that runs parallel to the imaginary line ○ Ex: rectus femoris (straight muscle of the thigh/femur) Oblique ○ Muscles runs slant 2. Relative Size of the Muscle Maximus  ○ Largest Convergent ○ Ex: gluteus maximus ○ Fascicles merge toward a Minimus single insertion tendon ○ Smallest ○ Ex: pectoralis major Longus Parallel ○ Long ○ Length of fascicles run 3. Number of Origin parallel to the long axis of the Biceps muscle ○ Two origins ○ Ex: sartorius ○ Ex: biceps of muscle of the Pennate arm has two heads ○ Short fascicles attach Triceps obliquely to the central ○ Three origins tendon Quadriceps ○ Ex: extensor digitorum ○ Four origins ○ Fascicle insert only to one 4. Location of the Muscle’s Origin side of the tendon and muscle and Insertion Bipennate Ex: sternocleidomastoid muscle ○ Fascicle insert into opposite ○ Origin: sternum and clavicle site or from several different ○ Insertion: mastoid process sides 5. Shape of the Muscle ○ Ex: rectus femoris Deltoid Fusiform ○ Triangular ○ Spindle-shaped muscle with ○ Ex: deltoid muscle an expanded belly 6. Action of the Muscle (midsection) Action ○ Ex: biceps brachii ○ Flexor, extensor, and adductor ○ Ex: adductor muscle of the thigh, extensor muscle of the wrist T. ARRANGEMENT OF FASCICLES Circular ○ Arranged in concentric rings ○ Surrounds external body opening which closes by contraction ○ Ex: orbicularis oris (mouth) and oculi (eyes) U. MUSCLES OF THE FACE wrinkles forehead horizontally Nerve Supply Facial nerve Occipitalis Overlies posterior occiput By pulling on the epicranial aponeurosis, fixes origin of frontal belly Posterior Scalp: Occipitalis Origin Occipital bone and temporal bone Insertion Galea aponeuronica Action Pulls scalp posteriorly Nerve Supply Facial nerve Orbicularis Oculi Superficial muscle of expression Thin, flat sphincter muscle of the V. MUSCLES OF THE HEAD eyelid Occipitofrontalis (Epicranius) Surrounds the rim of the orbit Bipartite muscle consisting of the Orbicularis Oculi frontal and occipital bellies connected by the epicranial Origin Frontal bone, maxilla, aponeurosis and medial palpebral ligament; lacrimal bone Muscle of the scalp Covers forehead and dome of the Insertion Lateral palpebral raphe skull; no bony attachment and superior and inferior tarsi medial Anterior Scalp: Frontalis (Frontal Belly) Action Blinks and closes eyelids Origin Epicranial aponeurosis Nerve Supply Facial nerve (Cranial VII) Insertion Skin of eyebrow and root of nose Orbicularis Oris Action Raises eyebrows, Encircles the mouth (orem)  Muscle of facial expression Masseter Kissing and whistling muscle Origin Temporal bone Orbicularis Oris Insertion Ramus of mandible Origin Mandible and maxilla Action Raises the mandible Insertion Sphincter-like muscle at against the maxilla with angle of the mouth great force Action Superficial = close, Nerve Supply Trigeminal nerve protrudes lips (Cranial V) Deep = presses lip against teeth Buccinator Thin, horizontal cheek muscle Nerve Supply Facial nerve Principal muscle of the cheek Deep to the masseter W. MUSCLES OF MASTICATION Temporalis Buccinator Fan-shaped muscle that covers part Origin Molar region of the of the temporal, frontal, and parietal maxilla and mandible bones Insertion Orbicularis oris Temporalis Action Compresses cheek (as in Origin Temporal fossa and whistling and sucking, temporal fascia draws corner of the mouth laterally) Insertion Coronoid process, anterior ramus of Nerve Supply Facial nerve mandible Action Closes jaw, elevates and Zygomaticus retracts the mandible Muscle pair extending diagonally against maxilla with from cheekbone to corner of the great force mouth Nerve Supply Trigeminal nerve Adjacent to buccinator Zygomaticus Masseter Origin Zygomatic bone Powerful muscle that covers lateral aspect of the mandibular ramus Insertion Skin and muscle at the Superficial muscle of corner of the mouth mastication/chewing Action Raises lateral corners of  mouth upward (smiling) to its midline Nerve Supply Facial nerve Insertion Skin and muscle of lower lip Risorius Action Draws lower lip Slender muscle inferior and lateral to inferiorly (pout) zygomaticus Nerve Supply Facial nerve Risorius Origin Lateral fascia associated Depressor Anguii Oris with masseter muscle Small muscle running from mandible to lower lip Insertion Skin at angle of mouth Lateral to depressor labii inferioris Action Draws corner of the lip Depressor Anguii Oris laterally; tenses lips; synergist of zygomaticus Origin Body of mandible below incisors Nerve Supply Facial nerve Insertion Skin and muscle at angle Levator Labii Superioris of mouth below insertion of zygomaticus Thin muscle between orbicularis oris and inferior eye margin Action Draws corners of mouth down and laterally (a Levator Labii Superioris “tragedy mark” grimace); Origin Zygomatic bone and zygomaticus antagonist infraorbital margin of Nerve Supply Facial nerve maxilla Insertion Skin and muscle of upper X. EYE MUSCLES lip Superior Rectus Action Opens lip; raises and Upgaze, upward; with some furrows upper lip contribution – inferior oblique Rotate medially Nerve Supply Facial nerve Lateral Rectus Outward Depressor Labii Inferioris Toward the ear Small muscle running from mandible Inferior Rectus to lower lip Down gaze, downward; with some Depressor Labii Inferioris contribution – superior Rotate laterally Origin Body of mandible lateral Medial Rectus  Inward Movements of vertebral column and Toward the nose head Superior Oblique Part of the collarbone Rotate medially Stenrocleidomastoid Inferior Oblique Rotate laterally Origin Sternum and clavicle Insertion Lateral surface of the Y. MUSCLES OF THE NECK mastoid process; nuchal Muscles that move the head and line of occipital bone shoulder girdle Platysma Action Draws head towards Unpaired, thin, sheetlike superficial shoulder of the same side, rotates head to neck muscle; not strictly a head opposite side, flexes muscle, but plays a role facial cervical part, assist in expression elevating the thorax Covers anterolateral neck (anterior neck) Nerve Supply Accessory nerve (cranial X1) and branches of Platysma cervical spinal nerves C2 and C3 (ventral rami) Origin Fascia of chest (over pectoral muscles and deltoid); pectoralis Scalenes deltoid Anterior, middle, posterior More laterally than anteriorly on Insertion Lower margin of mandible, and skin and neck muscle at corner of the Deep to platysma and mouth sternocleidomastoid Action Tenses neck of skin Scalenes (during shaving); helps Origin Transverse processes of depress mandible; pulls cervical vertebrae lower lip back and down, producing downward sag Insertion Anterolaterally on first of mouth; “sad clown two ribs face” Action Elevate first two ribs (aid Nerve Supply Facial nerve in inspiration); flex and rotate neck Sternocleidomastoid Nerve Supply Cervical spinal nerve Neck muscle classified with lateral cervical muscles Arises from two heads, Splenius Capitis ○ Abdominal Intrinsic muscle of the spine Pectoralis Major Posterior triangle of the neck Vertebral column and head Origin Sternum, clavicle, and movements first to sixth ribs Splenius Capitis Insertion Proximal humerus Origin Lower half of Action Adducts and flexes the ligamentum nuchae and humerus spinous process of 7th cervical vertebrae – 3rd or 4th thoracic vertebra Intercostal Muscles: ➔ Found in between the ribs Insertion Mastoid process of ➔ For breathing temporal bone and External Intercostals occipital bone Muscles of thorax from tubercles of Action ✓Supports head erection the ribs behind to the cartilages of ✓Draws head directly the ribs in front backwards Fibers are directly obliquely ✓Draws head to one downwards and laterally on the back side of the thorax, and downward, Slight rotation, turning forward, and me