Human Anatomy – Class Notes Skeletal System



Skeletal SystemThere are 206 bones in the human bodyThe Skeletal system performs five major functionsSupport and StructureThe skeletal system is the body’s frameworkIt supports the body and provides structure much like a building under construction has a frame to support the walls and ceilingsExoskeletons are outside – crabs and roaches have Exoskeletons, - they have NO backboneInternal or ENDOSKELETON – this skeleton is inside the body – birds, monkeys, snakes, and humans have endoskeletonsMovementTo provide movement, you must have musclesBones attached to other bones via ligaments (bones are held together by ligaments)Muscles attached to bone via tendonsMuscles and bones work together to move the bodyProtection-the skeletal system protects vital tissues and organs- For example: the skull protects the brain, the ribcage protects the lungs, and the backbone protects the spinal cordStorage area for blood clotting Stores products that help body functionFor example: bleeding – the body forms a blood clotting agent that comes from the bonesBlood ManufacturingNew blood cellsRed blood cells are producedThere are 27 trillion red blood cells in the body Marrow is where new red blood cells formBlood travels through veinsBones and CartilageBones are the strongest material in the body – bones represent only 14% of body weightWhen a person is born, the majority of their bones are made of cartilage Cartilage is more flexibleFrom 7 months to age 25 cartilage gradually is replaced by bonesBabies have a “soft spot” on their head because the skull starts out as cartilage to fit through the birth canal - eventually the bones of the skull fuse together to create boneBones continue to reform through lifeCartilage provides a smooth surface for bones to glide across and bend and is more slippery than ice You will find cartilage in your knee, nose, and elbow - and is located between bonesBreakdown in cartilage causes bone to rub against bone, this can be painful and can also lead towards arthritisYour knee absorbs the most pressure from the body - Cartilage provides a cushionJointsJoints keep bones far enough apart so they don’t rub together and they hold bones in placeThe skeleton is moveable because of the joints it containsThe FOUR types of joints areHinge Joint – only moves in one directionExample: elbow and knee are the two main areas with hinge jointsBall and Socket – this joint is in the shoulder and allows for movement in many directionsPivot Joint – this joint is found in the neck – you can move and twist the neck back and forth, up and downFixed Joints – These joints do not move – the bones come together but there is no movementExample: the skull is a fixed jointInjuryThere are two types of fracturesSimple fracture – a bone breaks but it doesn’t come through the skinCompound fracture – a bone breaks and pushes through the muscle and skinLigamentsConnect the bone to boneSprain – this occurs when a ligament is torn or over stretchedMuscle – a muscle can be strained if it is over stretched Cramp – a sudden strong contraction of a muscle – ex: charley horse or a knotTHE SPINEThere are curvature abnormalities in the spine, they include1) Scoliosis: an abnormal curvature that usually occurs in the thoracic region of the spine.The spine is normally “S” shaped but scoliosis is more of a curveIt is more common in girlsIt can be treated surgically or with a braceA person with scoliosis may have one leg longer than the other2) Kyphosis: an extreme thoracic curvature that creates a condition called a hunchback- it is caused by rickets (a bacterial infection) and/or tuberculosis of the spine3) Lordosis: This is an extreme lumbar curvature- it affects people with potbellies or pregnant women- it is also referred to as swaybackTHE BONY THORAXThis is also referred to as the thoracic ribcageIt is the point of attachment for the neck, head, back, chest, and shoulder musclesIt is made up of 3 parts12 thoracic vertebrae -divides the ribcage in the backSternum or breastbone-forms the anterior midline of the ribcageRibs-there are 12 paired flat bones = 24 total ribs-forms a lateral or side bar of the cage-ribs are directly attached to the thoracic vertebrae in the back-TRUE Ribs are the 1st 7 pair of ribs (totaling 14) – they are attached anteriorly to the sternum by hyaline cartilage-FALSE Ribs – these are the bottom 5, indirectly attached to the sternum by cartilage above them-FLOATING Ribs- the last two ribs are false ribs called floating ribs because they have no attachment; they are only attached via muscles hence floating. The skeletal system is broken down into 2 divisionsAxialAppendicularAXIALAn axis is an imaginary line – for the skeletal system it goes straight down the bodyThere are 80 bones in the Axial divisionThese bones form a long axis of the body and skeletal systemThere are 3 regionsA) skullB) vertebral column (or backbone)C) bony thorax (or rib cage)The three regions have a job – to protect the head, neck and torso which is the brain, spinal cord, and lungs & heartThe Skull is the most complex part of the axial systemTWO KEY TERMS for axial systemPAIRED- 2 identical bones for example: in your skull the temporal boneARTICULATE – connects with – Ex. Your radius and ulna are connected to the humorousThe axial is divided into planesTRANSVERSE – HorizontalSuperior and inferiorFRONTAL – Vertical, head to foot or up and down-anterior (front) and posterior (back)SAGITAL – vertically right to leftMedial (toward the midline) and lateral (away from the midline)Proximal – near the trunkDistal – away from the trunkAppendicular Skeleton– it helps us move-Made up of upper and lower limbs (arms and legs)-girdles attach the limbs to the axial skeleton- all the bones help us move and manipulate our environmentUPPER LIMBS OF THE APPENDICULAR SYSTEMOne of the most important bones is the pectoral girdle or the shoulder girdle (there are two in our body)Attaches upper limb to trunk of body and anchors musclesEach girdle is made up of two bones Clavicle – also called the collarbone. It is the anterior boneScapula – or the shoulder blade is the posterior boneBONES IN THE UPPER LIMBSYou have 30 bones in the upper limb27 bones in a handHumerus – IN THE UPPER ARM, AND IS THE ONLY BONE IN THE UPPER ARM, IT IS THE LARGEST AND LONGEST BONE IN UPPER LIMBSALSO CALLED THE FUNNY BONERadius – CONTAINED IN THE FOREARM – ENDS CLOSER (PROXIMAL ENDS) TO THE TRUNK CONNECT WITH THE HUMERUS TO FORM ELBOWUlna – DISTAL ENDS CONNECT WITH HAND TO FORM THE WRIST AND IS IN THE FOREARMBones in the hand8 carpals – bones that form the wrist5 metacarpals –(form the palm)12 phalanges (fingers and the thumb)**the thumb is also called the pollexTHE SKULLThere are 22 bones in the skull not including the 3 bones in each of our earsThe skull is broken into two sets, the cranial and facial CRANIAL or CRANIUM– Helmet or top part of the skullThe cranium has 8 bones – 2 paired and 4 unpairedPaired bones include the parietal and TemporalUnpaired bones include the frontal, occipital, ethmoid, and sphenoidPAIRED BONESFRONTAL – forms the front of the head (forehead) and the eye sockets also called the superior orbits Also includes he paranasal sinuses which are the mucus lined cavities that filter airOCCIPITAL – forms the base and back of the headETHMOID - forms the nasal cavity and the septum, is at the base of the craniumSPENOID – articulates or connects with all cranial bones, it is also called the keystone of the cranium and is located at the base of the craniumUNPAIRED BONESPARIETAL – forms the roof of the craniumTEMPORAL – forms the lower outer side of the craniumThe –oids ethmoid and sphenoid are found in the inside, they are the internal bones in the craniumThe –als Frontal, Parietal, Occipital, and Temporal are the external bones of the craniumFACIAL – Jaw, eye sockets, provide cavities for the eyes and noseThere are 14 facial bones, 6 paired and 2 unpairedPAIRED BONESUNPAIREDNASAL – Bridge of noseLACRIMAL – anterior medial orbits, tear sacsZYGOMATIC- cheekINFERIOR NASAL CONCHA- side walls of nasal cavityMAXILLAE – eye socket, nasal cavityPALATINE –floors of orbits, walls of nasal cavities, and portion of the hard palateMANDIBLE – jaw bone VOMER – poster and inferior parts of nasal septumHyboid Bone – not officially part of a bone. It does not articulate or connect with any other bone. It’s the little bone bit below the jaw; it’s the point of attachment for the tongue, throat, and neck musclesTHE VERTEBRAL COLUMNAlso called the backboneThere are 26 bones in the vertebral columnAnd it is broken down into 5 piecesCervical division – has 7 vertebrae and is located in the neckThoracic division – has 12 vertebrae and is located in the chest area, the rib cage connects with it.Lumbar division – there are 5 vertebrae and is located in the lower back (small of the back)Sacrum division – there are 5 vertebrae and it articulates with the pelvis; it is fused or melted togetherCoccyx – it had 3 fused vertebrae and is also called the tailboneAnswersAppendicular Skeleton: the Upper LimbsFrom the Standard deviants videoThe appendicular skeleton helps us moveIt is made up of upper and lower limbs which are the arms and legsIt is made up of girdles which attach the limbs to the axial skeletonThe Pectoral Girdle is also called the Shoulder girdle – there are two in your body which means it is a paired bone- it attaches the upper limb to trunk of the body and it anchors muscles that move the limb- there are two bones in the pectoral girdle 1) the clavicle (collarbone): this is the anterior bone2.) the scapula (shoulder blade): this is the posterior bone There are 30 bones in upper limbThere are 27 bones in the handThe Upper arm contains one bone – the humerus - it is the longest and largest bone in the upper limb and it is the only bone in the humerus.The forearm contains two bones, the ulna and radius the proximal ends of the ulna and radius connect with humerus to form elbow The distal ends of the radius and ulna connect with the hand to form the wristThe hand: 8 carpals – bones of the wrist5 metacarpals – bones of the palm 14 phalanges – fingers and thumbs***Pollex is fancy word for thumb ................
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