Appendicular Skeleton and Muscular System

What is the fin fold theory?
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What is the fin fold theory?
Early vertebrates had a continuous lateral fin fold and when immediate parts of this fold were lost, paired fins were developed
What provides embryological evidence to this theory?
The limb-forming zone. The intermediate areas can still be induced
The big head reduces? The pectoral fin reduces? The median fin reduces?
The big head reduces yaw (side to side movement). The pectoral fin reduces pitch (up/down) The median fin reduces roll.
Describe the pectoral anatomy of gnathostomes.
Placoderms: earliest gnathostomes have pectoral anatomy built with dermal and cartilaginous elements
What is the basic layout of fins from proximal to distal?
Basal pterygiophores-radial ptergiophores-ceratotrichea/lepidotrichea
Describe pterygiophores
Made of cartilage and form in the proximal region from endochondral bone.
Pectoral Girdle in Chondrichthyans
Made of scapulocoracoid cartilage. Has to be larger as it lacks the stabilizing effect of bone
Pectoral Girdle in Osteichthyans (two main bones)
Scapula and coracoid are the two main bones
Pelvic Girdle
The only cartilage/bone of the girdle. No dermal component even in bony fish
What are the two types of sarcopterygian fins and what separates them?
Archipterygium- central pterygiophore axis down the middle. Radial pterygiophores extend from both sides

Crossopterygium- Pterygiophore axis on the posterior side. Only have radial pterygiophores coming from thee axis to the anterior border of the fin. More closely resembles tetrapod limb.
What are the three main components of the limb? At what component did tetrapods begin to significantly deviate from fish?Stylopodium: proximal region (brachium in front leg, femur in hindleg) Zeugopodium: Middle portion (Radia, ulna; tibia, fibia) Autopodium: Distal region (tetrapod deviation)Patterns of HoxD expression? Why arent they the best indicatorExperiment used the HoxD results of the zebrafish which is a telost, not an ancestor of the sarcopterygii. Others believe it might be a result of the curving of the pterygiophore axisWhat are the two types of bones that make up the pectoral girdle and give two examples from each bone?Dermal bone: clavicle and cleithrum Endochondral bone: scapula and coracoidWhat makes up the pelvic girdle?Endochondral bone: ilium, ischium, and pubis. No dermal bonesWhat key trait separates tetrapods from reptilomorphs?Tetrapods only have four digits on their forelimbsName three amphibian adaptations.Fused radius and ulna Fused tibia and fibia Extended tarsals that add another unfolding to the limb while jumpingAppendicular features of the reptilomorph skeletonFive digits on each limb. Hinge joint for ankle develops here, not seen in tetrapods. Astragalus- central element of the foot that articulates with the calcaneous to form a single unit.Appendicular Skeleton of TurtlesShoulder is internal to the ribs Shell is made up of ribs that have expanded and reduced intercostal space Carpical Ridge- scleotome cells migrate down along muscles to form the bones of the thorax but turtles have a ridge on the top of the body to attract sclerotome cells to lateral positions. Axial on outside, appendicular on insideWhat are the appendages like for early flying creatures?Lost fifth digit and thumb but digits 2, 3, and 4 are present. Really long forth finger to make up wingWhat alterations does the bird have in its appendicular skeleton to facilitate flying?Wishbone- fusion of clavicles Carpometacarpus: carpals and metacarpals of the two posterior fingers fuse to form long bone Pelvic girdle fuses and forms synsacrum for stabilityHow do smooth muscles attach with proteins to the cell membrane?In a cross-helical arrangementWhat allows a smooth muscle to contract as a unit from one electrical signal?Gap-junctionsDescribe the layout of a smooth muscle and its layersLumen is the space- lining is developed from the endoderm layer Smooth muscles comes from the splanchnic layer of the lateral plate mesoderm Inner layer- cells laid end to end (Squeezing action) Outer layer- cells are perpendicular (act to shorten the digestive tract)How are cardiac muscle cells associated with one anotherIntercalated disks- think interdigitation Gap junctions are also present at the end of these disks. Mechanical linking spread tension of the contraction through the heart`Describe the basic organization of skeletal muscle?Myoblasts fuse together to form myofilaments (endomysium covers fibers) Myofilaments are grouped into myofibrils Fibrils are grouped into fascicles (these are wrapped in perimysium) Fascicles come together to form the muscle body which is wrapped in epimysiumWhy do we need tendons?Joints would be bulky and impede movements without them Tendons have elastic energy Tendons allow motion from a distanceWhat are the differences between slow twitch muscle fibers and fast twitch muscle fibers?Slow twitch- highly vascularized, contains myoglobin Fast twitch- less vascularized, no myglobin, fewer mitochondriaWhat are tonic skeletal fibers?Muscle that is fused in cases where posture is important (long sustained contraction). Important in stationary animals that need to hold a postureWhat is the main factor in the amount of force a muscle can generate?Increasing diameter (the cross-sectional area) is the main factor that increases forceWhat are the three types of muscle architecture?Strap shaped: long parallel fibers with broad attachment (good for long-distance contraction) Fusiform- fibers lead to narrow tendons Pennate (unipennate/bipennate)- allows a greater number of short fascicles to be packed into a space. Muscles generate comparably more force per volume. Reduction in movement. Force has a vertical and horizontal componentDescribe how location of muscle attachment affects strength and speed.Proximal insertion- speed Distal insertion- strengthName the four criteria of muscle homology in order to their likelihood to be the first to deviateSimilar function (analogous) Similar attachment Similar nerve supply Similar embryonic originWhere does each muscle type come from in the embryo?Skeletal muscle- somites (myotomes) Cardiac muscle/smooth muscle- lateral plate (splanchnic mesoderm)Describe the two main muscle groups and what separates the two?The horizontal septum separates the hypaxial group (dorsal, above the septum) and the epaxial group (ventral, below the septum)Describe what happens to the somite muscles once they reach the head region.Segmentation continues but fades off. It gets smaller and smaller and sometimes doesnt even form complete arrangements. These are called somitomeres.What are branchniomeric muscles?Muscles that develop in the pharynx wall and attach to the visceral arches. Continuous with the hypaxial, epaxial regions. Epibranchial (above the gills). Hypobranchial (below the gills)Describe the innervation of the muscles in gnathostomes.Epaxial- innervated by the dorsal rammus of the spinal nerve Hypaxial- innervated by the ventral rammus of the spinal nerveCyclostome axial musclesNo hypaxial/epaxial muscles, no horizontal septum, segmentally innervated by spinal nervesChanges in axial musculature in tetrapodsHorizontal septum is in a more dorsal location. Epaxial muscles have narrowed considerablyWhat is the role of epaxial muscles in tetrapods?Less important as tetrapods dont really undulate Smaller but specialized for dorso-ventral movement of the vertebral column, more flexibilityWhat are the three hypaxial muscle groups?Subvertebral group- ventral to the vertebral column, acts on vertebral axis, and assists the epaxial muscles in supporting the body and bending the column Ventral group- includes the rectus abdominus and supports the abdomen. Contriubutes to lateral and ventral fexion of the trunk Lateral group- on the flank and forms several layers. Consists of the obliques and transverse abdominus. Fibers run at different anglesWhat does cranial nerve V innervate?First arch. Mandibular muscles (masseter, temporalis, ear muscle)What does cranial nerve VII innervate?Hyoid arch (Second arch). Branchial muscles in the shark. The stapes is also innervated by thisWhat muscle expands and becomes facial muscles? Why does this happen?The constrictor coli. Originates probably for sucklingWhat innervates the third and fourth arches?CN 9 and 10 innervate the third and fourth arches. In mammals these muscles move internally around the pharynx and are less superficialCranial nerve 11 and 12 innervate what?11- epibranchial muscles (trapezius) 12- hypobranchial muscles (tongue)Where do appendicular muscles originiateHypaxial muscles, myotomes migrate to populate limb buds. muscles are innervated by ventral rami of spinal nervesWhat is the only secondary appendicular muscle in the pelvic limb musclePsoas major