Chapter 10 Muscle Tissue - Fudan Universityfdjpkc.fudan.edu.cn › _upload › article › files › e9 › 59 › c7afd... · 2018-01-20 · 2 10-7 H E Iron-Haemotoxylin Transverse

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刘 琼 副教授

复旦大学基础医学院解剖与组织胚胎学系

Department of Human Anatomy, Histology and Embryology

Human Histology & Embryology

Chapter 10Muscle Tissue

3 Types of Muscle Tissue

• Skeletal muscle• attaches to bone, skin or fascia• striated with light & dark bands visible with scope • voluntary control of contraction & relaxation

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3 Types of Muscle Tissue

• Cardiac muscle• striated in appearance• involuntary control• autorhythmic because of built in pacemaker

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3 Types of Muscle Tissue

• Smooth muscle• attached to hair follicles in skin• in walls of hollow organs -- blood vessels & GI• nonstriated in appearance• involuntary

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Functions of Muscle Tissue• Producing body movements• Stabilizing body positions• Regulating organ volumes

• bands of smooth muscle called sphincters

• Movement of substances within the body• blood, lymph, urine, air, food and fluids, sperm

• Producing heat• involuntary contractions of skeletal muscle (shivering)

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Muscle Histology

• Elongated cylindrical cells = muscle fibers• Plasma membrane = sarcolemma• Transverse (T) tubules tunnel from surface to center of each fiber• Multiple nuclei lie near surface of cell• Cytoplasm = sarcoplasm

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H E Iron-Haemotoxylin

Transverse Tubules

• T (transverse) tubules are invaginations of the sarcolemma into the center of the cell

• filled with extracellular fluid• carry muscle action potentials down into cell

• Mitochondria lie in rows throughout the cell• near the muscle proteins that use ATP during contraction

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Myofibrils & Myofilaments

• Muscle fibers are filled with threads called myofibrils separated by SR (sarcoplasmic reticulum)

• Myofilaments (thick & thin filaments) are the contractile proteins of muscle

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Sarcoplasmic Reticulum (SR)

• System of tubular sacs similar to smooth ER in nonmuscle cells

• Stores Ca+2 in a relaxed muscle• Release of Ca+2 triggers muscle contraction

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Sarcomere• Filaments overlap in repeating patterns• Unit structure is called sarcomere• Separated by Z discs• Darker area = A band associated with thick filaments• H zone has no thin filaments• I band has thin filaments no thick filaments

Functional Structure• Thick filament (myosin) has moveable heads (like “heads” of

golf clubs)• Thin filaments (actin) are anchored to Z discs

• Contain myosin binding sites for myosin head• Also contain tropomyosin & troponin

• Tropomyosin blocks myosin binding site when muscle is at rest

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Sliding filaments and sarcomere shortening in contraction.Diagrams and TEM micrographs show sarcomere shortening during skeletal muscle contraction. (a) In the relaxed state the sarcomere, I band, and H zone are at their expanded length. The springlike action of titin molecules, which span the I band, helps pull thin and thick filaments past one another in relaxed muscle. (b) During muscle contraction, the Z discs at the sarcomere boundaries are drawn closer together as they move toward the ends of thick filaments in the A band. Titin molecules are compressed during contraction.

Ø Sarcolemma invaginate into sarcoplasm to form a transverse distributed tubular systemØFunction: transfer stimulation into cytoplasm (A-I band boundary)

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Ø Sarcoplasmic reticulum enlarge to form flattened sacØ Function: store and release Ca 2+ (Ca2+ pump on membrane)

One T-tubule + two terminal cisternae

Neuromuscular junction

MEP: motor end-plateNB: nerve bundleS: skeletal muscle

Neuromuscular junction

Structures of NMJ Region

• Synaptic end bulbs are swellings of axon terminals

• End bulbs contain synaptic vesicles filled with acetylcholine (ACh)

• Motor end plate membrane contains 30 million ACh receptors.

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HE Special stain

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Tissue Features:• Striated (same contractile machinery)• Self-excitatory and electrically coupled• Rate of contractions modulated by autonomic nervous system

• innervation is neuroendocrine in nature (i.e. no “motor end plates”) Cell Features:• 1 or 2 centrally placed nuclei• Branched fibers with intercalated discs• Numerous mitochondria (up to 40% of cell volume)• Sarcoplasmic reticulum & T-tubules appear as diads at Z lines

Smooth Muscle • Fusiform, non-striated cells• Single, centrally-placed nucleus• Contraction is non-voluntary• Contraction is modulated in a neuroendocrine manner• Found in blood vessels, GI and urogenital organ walls, dermis of skin

(a) Skeletal muscle

Description: Long, cylindrical,multinucleate cells; obviousstriations.

Function: Voluntary movement;locomotion; manipulation of theenvironment; facial expression;voluntary control.

Location: In skeletal musclesattached to bones oroccasionally to skin.

Photomicrograph: Skeletal muscle (approx. 460x).Notice the obvious banding pattern and thefact that these large cells are multinucleate.

Nuclei

Striations

Part ofmuscle fiber (cell)

(b) Cardiac muscle

Description: Branching, striated, generally uninucleate cells that interdigitate atspecialized junctions (intercalated discs).

Function: As it contracts, it propels blood into the circulation; involuntary control.Location: The walls of the heart.

Photomicrograph: Cardiac muscle (500X);notice the striations, branching of cells, andthe intercalated discs.

Intercalateddiscs

Striations

Nucleus

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(c) Smooth muscle

Description: Spindle-shapedcells with central nuclei; nostriations; cells arranged closely to form sheets.

Function: Propels substancesor objects (foodstuffs, urine,a baby) along internal passage-ways; involuntary control.

Location: Mostly in the wallsof hollow organs.

Photomicrograph: Sheet of smooth muscle (200x).

Smoothmusclecell

Nuclei