WEEK 11 HANDOUT FOR BIO 03051, VERTEBRATE ZOOLOGY: SUPPORT AND MOVEMENT
Text (7th ed.): Ch. 6. Lab manual may also be of use.
4/4/00 Dr. W. Crone (303 FTZ, 629-7439, cronewil@hvcc.edu, http://www.hvcc.edu/academ/faculty/crone/index.html)
possible web site: http://www.meddean.luc.edu/lumen/MedEd/GrossAnatomy/dissector/mml/index.htm (LUMEN Master Muscle List: information and graphics on all human muscles)
HVCC audiovisuals: VT 3385,"Eyewitness: Skeleton" (to be seen in lecture)
VT 1081,"Human Musculature" (cadaver-based review of human muscles)
PROTECTION is achieved by the integument or external covering of an animal. Skin is the integument found in vertebrates and has two main layers: an epidermis (from ectoderm) of several cells in thickness of stratified squamous epithelial tissue, and a dermis (from mesoderm) of connective tissue below the epidermis. The dermis contains the support and nourishment for the epidermis and its structures.
SUPPORT is achieved through a rigid endoskeleton of either cartilage or bone. Connective tissue consists of cells, a matrix (ground substance), and fibers (typically collagen).
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cartilage: |
chondrocytes in large lacunae in a rubbery matrix with collagen. No blood vessels, so generally slow healing. Lighter than bone. |
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bone: |
osteocytes in small lacunae in a collagen matrix hardened by the mineral hydroxyapatite (calcium phosphate). Many blood vessels throughout bone, as highlighted by the many canals (e.g., central or Haversian) seen in sections. |
In general, there are two types of bones:
Dermal (membranous) bone forms in the dermis of the skin. Examples: our facial bones. Endochrondal bone forms the long bones from cartilaginous precursors. Osteoblasts (bone-forming cells) start along the middle (diaphysis) of the long bone and the breakdown within forms the marrow cavity. The end of the long bone, the epiphysis, keeps growing until adulthood. Examples: the long bones of our limbs, with compact bone on the outside and spongy (cancellous) bone inside.
A survey of the vertebrate skeletons seen so far range from the notochordal support of the hagfish, the high spinous processes (and hence, much epaxial muscle) of the bony fish, to the varied axial (skull and spine) and appendicular (limbs) skeletons seen in the tetrapods.
MOVEMENT is achieved by muscles, which work by contracting against their attachments to bones via tendons (or if broad, aponeuroses). These tendons are the outgrowths of the connective tissue (epimysium) surrounding the muscle. There are three types of muscles:
1) involuntary smooth muscle, with slow, sustained contractions, found around the gut, blood vessels, and such places as arrector pili muscles (goosebumps)
2) involuntary, striated cardiac muscle, branching, automatically contracting on its own, with specially modified electrical plates (intercalary discs) on the ends of the muscles
3) voluntary, striated skeletal muscle for movement
Briefly, muscles work by contraction. Let's concentrate on skeletal muscle (of particular interest to PES!). The striations represent light and dark patterns of myofibrils, or the bundles of contractile proteins within skeletal muscle cells. Actin and myosin within the myofibrils actually create the light and dark bands, with the light bands containing only the thin actin and the dark bands containing both actin and the thicker-fibers of myosin. The myofibril works by a unit called the sarcomere.
In the sarcomere during contraction, the attached (to a Z line) actins slide over the myosins to shorten the sarcomere. These contractions occur with the assistance of calcium to free up attachment sites for the myosin heads along the actin, and ATP (adenosine triphosphate) to power the contraction of the myosin head attached to the actin. Nerve impulses drive muscle contractions through neuromuscular junctions, by allowing the release of calcium stored in modified endoplasmic reticulum (the terminal cisternae of the sarcoplasmic reticulum). Exercised muscle will enlarge; underutilized muscle will atrophy.
Major movements: flexion, extension, adduction, abduction, rotation
Major muscles (mammalian, especially human) to be familiar with by this point in the course (m.: abbreviation for muscle)
head and neck:
facial muscles (expression) (e.g., zygomaticus major m.)
temporalis m., masseter m. (chewing)
strap muscles (e.g., sternohyoid m.) attached to hyoid
pectoral girdle:
pectoralis major m. (flexes humerus)
latissimus dorsi m. (extends humerus)
trapezius m. (shrug and squares shoulders)
deltoid m. (on shoulder, abducts humerus)
rotator cuff, e.g., supraspinatus m. (assists in holding humeral head in shoulder socket)
upper extremity:
biceps brachii m. (flexes elbow)
triceps brachii m. (extends elbow)
abdomen:
external, internal oblique muscles
rectus abdominus m. (all are body wall muscles)
pelvic girdle:
gluteus maximus m. (hip extensor, power for hills, stairs)
gluteus medius m., tensor fasciae latae m. (assist in stabilizing hip and knee while walking)
lower extremity:
quadriceps (e.g., rectus femoris m.) extend knee
hamstrings (e.g., biceps femoris m.) flex knee
adductors (e.g., gracilis m.) adduct thigh
gastrocnemius m. (distinctive calf muscle)
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Please send comments and questions to: cronewil@hvcc.edu
Copyright 1999, 2000 by Wilson Crone
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This web page last updated on April 7, 2000