chapter 10 - muscle tissue

3 types of muscle

skeletal - moves & positions the body

smooth - pushes fluids & solids along digestive tract & regulates artery (blood vessel) diameter

cardiac - pushes blood through circulatory system

functions of skeletal muscle

skeletal movement - pulls tendons to move bones

maintain posture & body position

support soft tissues - ex. muscles of the abdominal wall & pelvic cavity

guard entrances & exists - openings of the digestive & urinary tracts

maintain body temp

store nutrients - glucose, lipid & even muscle proteins used during fasing

roots associated with muscle

myo, mys = muscle (myoneural junction = muscle nerve junction)

sarco - flesh (Gk) 

sarcolemma - cell membrane of a muscle cell 

sarcoplasm - cytoplasm of a muscle cell

sarcoplasmic reticulum - modified endoplasmic reticulum of a muscle cell

muscle tissue

muscle consists of muscle fibres (myofibers) wrapped in a connective tissue called the endomysium

a number of fibres are wrapped together in periosteum to form a fascicle, while fascicles are bundled together to form a muscle, which is wrapped in epimysium or deep fascia

the 3 connective tissue layers come together to form a tendon

Individual fibres are full of contractile organelles called myofibrils, which fill the cell and displace the nuclei to one side

Myofibrils are a systematic arrangement of proteins (myofilaments) which form the contractile unit of the muscle called a sarcomere, which give muscle its striated apperance

connective tissues around

whole muscle - epimysium

fascicles - perimysium

cells (myofibers) - endomysium

muscle attachments

the collagen fibres of 3 different connective tissue layers come together at the ends of the muscle to form tendons (bundles) or aponeuroses (sheets)

structure - tendons in turn are continuous with matrix of the bone they are attached to

aponeuroses

plural 

layers of flat broad tendons with fewer vessels & nerves 

structure - typically both tendons and aponeuroses attach muscles to bones

nerve and blood supply

nerve and blood vessels penetrate epimysium together and branch through perimysium and endomysium

each cell is

• adjacent to capillaries

• Inverted by nerve fibre axons

skeletal muscle is made up of..

myofibrils - a bundle of smaller rod like structures

Myofilaments - even smaller structures/proteins make up myofibrils

development of skeletal muscle from myoblast to maturity

1.muscle fibers develop through the fusion of ebryonic mesodermal cells called myoblasts

2. most myoblasts fuse to form larger multinucleate cells

2. a few myoblasts remain with the tissue as myosatellite cells 

3. multinucleate cells differentiate into skeletal muscle fibers as they enlarge and begin producing the proteins involved in muscle contraction

tubules surrounding the myofibrils

tiny tubules called transverse tubules or T tubules penetrate the sarcolemma and travel deep into the cell surrounding the myofibrils

t tubules - conduct waves of electrical activity from the sarcolemma deep into the cell, providing the signal for the cell to contract

structure of myofibrils

bundles of thick and thin filaments (protein strands)

sarcoplasmic recticulem

sarcolemma - plasma membrane of the muscle fiber, has an intricate system of penetrating T - tubules that connect to a specialized smooth ER called sarcoplasmic reticulum (SR)

the SR stores and releases calcium ions which are important for muscle contraction

most SR ca2+ bound to calsequestrin protein

muscle fiber bands/sections

A band - (dark area) corresponds to thick filaments

• M line - line of proteins that connect the thick filaments

• H zone - lighter region contains no overlap

Zone of overlap - thin filaments protrude between thick filaments

I band - (light area) extends from A band to A band

• includes thin filaments, with no overlap with thick filaments

• includes Z lines - anchor thin filaments

sarcomere - extends from Z line to Z line 

• functional unit of the muscle cell

Protein titin anchors thick filaments to Z lines (actin)