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WSU BIOLOGY 315 - Joints and Muscles

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Lecture 8 Outline of Last Lecture I. External gross structure of bonesa. Basic partsb. Bone cellsc. Bone tissueII. Development of Bonea. 2 classes of boneb. Phases of endochondral ossificationc. how bones widenIII. JointsOutline of Current LectureI. Joints- Synovial Joints continueda. Articular disc b. Ligaments c. Nerves d. Blood vesselsII. The Temporomandibular JointIII. Musclesa. Development of muscles Current LectureI. Joints- Synovial Joints (continued)a. Articular disc (menusus)i. Discs or rings of fibrocartilage inside some synovial jointsii. Subdivide the joint cavityiii. Shaped differently on upper and lower surfaces 1. To allow 2 distinct types of movement 2. Allow the opposing bone-ends to fit together betteriv. Not present in all jointsv. Examples) Knee joint and jaw jointb. Ligamentsi. Under great tensile and compressive stressii. Re-enforce synovial jointsiii. Extra ligaments can be either1. Thickenings of the fibrous wall of the joint capsule2. Separate ligaments internal to the capsule3. Separate ligaments outside of the capsuleiv. When stretched or torn  sprainc. Nervesi. go primarily to the fibrous joint capsuleii. some pick up pain sensations BIOL_315 1nd Editioniii. some sensitive to the position of the joint capsule1. lets the brain know how our body is moving and how it is positiona. allows our brain to calculate how to maintain balance and coordinate movementd. blood vesselsi. supplies blood to the jointsii. vessels go primarily to the synovial membrane**the fact that the synovial joints are supplied by several different nerves and vessels, which overlap, means that you can damage some of these and enough will remain to sustain function and allow recovery**II. Example of a particular joint- The temporomandibular (Jaw) jointa. The bony parts of the skull that articulate at the temporomandibular joint (TMJ)i. Head of the mandibleii. Inferior part of the squamous temporal boneiii. (temporal bone + mandible= temporomandibular)iv. Head of the mandible is egg shapedv. Articular surface on the temporal bone has a complex shape1. Posteriorly concave = mandibular fossa2. Anteriorly convex= articular tubercle b. Bony surfaces are covered by articular cartilagec. Joint capsule encloses the jointi. Lateral of capsule is theickened as the lateral ligamentii. Within the capsule is articular disc1. Superior and inferior surfaces are shaped differentlyd. 2 kinds of movement i. Between the head of the mandible and the inferior surface of the articular disc = hing-like rotationii. When mouth is open wide, articular disc slides anteriorly onto the articular tubercle 1. Function of this is brace the head of the mandible against the articular tubercle, allowing jaw to withstand the force of a strong bite e. Joints can disarticulate (dislocate), the TMJ is one that can do so easily i. Joints that dislocate easily have shallow socketsii. Joints that have deeper sockets (like the elbow) do not dislocate as oftenIII. Musclesa. Muscles are easier to understand if they are grouped according to developmental origin and function.b. 4 functional groupsi. Musculature of the digestive tube (and other hollow organs)1. Develops from splanchnic mesoderm around the embryonic gut 2. Consists of smooth musclea. Acts to squeeze things throughb. Arranged in sheetsi. Inner circular sheet and an outer sheetii. Muscles of the body axis (trunk, neck and head)1. Skeletal muscle tissue2. Excludes the limbs3. Develop from myostomesa. About 40 myotomes develop in the embryonic bodyb. Arranged segmentally 4. during the 5th week of development a. each myotome splits into a dorsal and ventral partb. dorsal parti. epaxial mass (dorsal to the vertebral axis)ii. epimere (upper piece)c. ventral parti. hypaxial mass (ventral to the vertebral axis)ii. hypomere (lower piece)d. after the have formed, they divide further into medial and lateral parts e. Epaxial Massi. Medial part: becomes the deep, short muscles of the back.Remain segmented, one vertebrae to the next. Function is to move or stabilize the individual vertebrae.ii. Lateral part: long muscles of the back- the erector spinae group of muscles. These run down the whole length of the back and function to extend the spine. f. Hypaxial massi. Medial part: located just ventral and lateral to the vertebral column, becomes the prevertebral muscles in theabdomen. 1. Example) the psoas major and quadratous lumborumii. Lateral part: thorax region. Largest part of the hypaxial mass runs between successive ribs. Gives rise to intercostals muscles (good example of segmentation). Function to move the ribs to produce breathing movements. Further down the body, external and internal oblique muscles and the transverse abdominis are lateral hypaxial muscles. Producing a strong abdominal wall to resist pressure from internal organs. Rectus abdominis alsodevelops from the ventral hypaxial mass. g. Axial muscles of the head: 2 sets in the head belong to the axial-muscle group: tongue muscles extrinsic eye musclesiii. Limb muscles1. Skeletal muscle tissue2. The 4 limbs arise as limb buds, somatic mesoderm enters these buds to form the limb skeleton, the ventral hypomere of the nearby myotomes enter to form the limb muscles3. Muscle forming tissue lies both dorsal and ventral to the skeletal elements4. Dorsal mass  primitive extensor muscles5. Ventral mass  primitive flexor muscles ** we have found that the same thing for both the axial muscles and the limb muscles. In both groups, the muscles that develop dorsally are extensors and the muscles that develop ventrally are flexors**iv. Muscles that originate around the pharynx 1. Skeletal muscle tissue, not smooth muscle2. Develops around the embryonic pharynx 3. Some stays in place around the pharynx, some migrates4. Includes some of the muscles of the larynx and the muscles of mastication, the thin muscles of our face, and maybe the trapezius and sternocleidomastoid muscles of the neck.c. Develop from the mesoderm germ


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