Muscle Tissue Overview

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Questions and Answers

Which of the following is NOT a characteristic of skeletal muscle cells?

They are uninucleated (correct)

They are elongated

They are multinucleated

They have peripherally located nuclei

What is the name of the contractile unit within a muscle cell?

Myofilament

Sarcolemma

Sarcomere (correct)

Sarcoplasmic reticulum

Which of the following is a type of muscle tissue that is NOT striated?

Skeletal muscle

Cardiac muscle

Smooth muscle (correct)

All of the above are striated

What is the name of the cell membrane of a muscle cell?

Sarcolemma (C) Signup and view all the answers

What is the function of the sarcoplasmic reticulum in muscle cells?

Stores and releases calcium ions (C) Signup and view all the answers

Which type of cell is responsible for bone resorption?

Osteoclast (D) Signup and view all the answers

What is the function of osteogenic cells?

To differentiate into other bone cells (B) Signup and view all the answers

Where are osteogenic cells located?

In both the periosteum and the marrow (A) Signup and view all the answers

What is the relationship between osteogenic cells and osteoblasts?

Osteoblasts are a type of osteogenic cell. (A) Signup and view all the answers

Which of the following is NOT a characteristic of osteoclasts?

Responsible for bone formation (A) Signup and view all the answers

Which of the following is NOT a feature of smooth muscle?

Striated appearance (C) Signup and view all the answers

What is the role of calmodulin in smooth muscle contraction?

It binds to calcium ions and activates myosin light chain kinase (D) Signup and view all the answers

What is the primary function of osteoblasts?

Form new bone tissue (B) Signup and view all the answers

How do osteocytes communicate with each other within the bone matrix?

Using long cytoplasmic processes that extend through canaliculi (B) Signup and view all the answers

Which statement correctly describes the difference between endomysium and perimysium?

Endomysium surrounds muscle fibers, while perimysium surrounds muscle fascicles (A) Signup and view all the answers

What is the significance of the inorganic salts, such as calcium phosphate and carbonate, in bone tissue?

They contribute to the hardness and rigidity of bone (D) Signup and view all the answers

What is the name given to the microscopic structural unit of compact bone?

Osteon (C) Signup and view all the answers

What is the term for non-cellular material found within the bone?

Extracellular matrix (B) Signup and view all the answers

What is the primary difference between lamellar bone and woven bone?

Lamellar bone is stronger due to its organized structure, while woven bone is weaker. (B) Signup and view all the answers

How does progesterone affect smooth muscle?

It inhibits smooth muscle contraction (A) Signup and view all the answers

What is the primary function of the mineral salts in bone?

Providing hardness and strength (A) Signup and view all the answers

Which of the following is NOT a characteristic of skeletal muscle?

Controlled by the autonomic nervous system (B) Signup and view all the answers

Where is compact bone typically found?

In the outer layer of bones, under the periosteum (B) Signup and view all the answers

What is another name for spongy bone?

Cancellous bone (C) Signup and view all the answers

Which of the following is NOT a characteristic of woven bone?

Organized into thin layers called lamellae (A) Signup and view all the answers

Which type of bone is associated with the adult skeleton?

Lamellar bone (B) Signup and view all the answers

Which type of skeletal muscle fiber relies primarily on anaerobic glycolysis for energy production?

Type IIb/IIx (C) Signup and view all the answers

What is the primary function of the spaces within spongy bone?

To reduce the weight of the bone (C) Signup and view all the answers

What is the primary function of the Z-line in a sarcomere?

Connecting point for actin filaments of neighboring sarcomeres. (D) Signup and view all the answers

What is the primary role of lamellae in the bone?

Organizing bone structure (A) Signup and view all the answers

What type of bone is found in the epiphyses of long bones?

Both compact and spongy bone (B) Signup and view all the answers

Which of the following characteristics is NOT associated with Type I skeletal muscle fibers?

Rapid, powerful contractions. (A) Signup and view all the answers

What is the name given to the membrane that covers the outer surface of bones?

Periosteum (A) Signup and view all the answers

What is the main difference between woven bone and lamellar bone?

Woven bone is less organized and laid down rapidly, while lamellar bone is organized and laid down slowly. (A) Signup and view all the answers

What type of bone is considered to be more mature?

Lamellar bone (D) Signup and view all the answers

What is the function of collagen fibers in the bone?

Providing flexibility and tensile strength (D) Signup and view all the answers

What is the role of the sarcoplasmic reticulum (SR) in muscle contraction?

To store and release calcium ions. (C) Signup and view all the answers

Which structure connects the muscle fiber to the tendon?

Muscle tendon junction. (D) Signup and view all the answers

Which of the following is an accurate comparison between compact and spongy bone?

Compact bone is dense and strong, while spongy bone is light and porous. (A) Signup and view all the answers

What is the functional unit of skeletal muscle contraction?

Sarcomere (C) Signup and view all the answers

Which of the following is a characteristic of skeletal muscle hypertrophy?

Increase in the number of myofibrils within each muscle fiber. (B) Signup and view all the answers

Which of these structures is NOT a component of a triad in skeletal muscle?

Myofibril (A) Signup and view all the answers

Signup and view all the answers

Study Notes

Muscle Tissue

Muscle tissue is of mesodermal origin
Muscle tissue is composed of specialized cells called myocytes that contract
Sarcomere is the cytoplasm of a myocyte
Sarcolemma is the cell membrane of a myocyte
Sarcoplasmic reticulum surrounds muscle fibers
Myocytes are composed of contractile protein filaments (myofilaments), including myosin and actin
Muscle tissue has three types: skeletal, cardiac, and smooth

Skeletal Muscle

Skeletal muscle cells are elongated, multinucleated, and have peripherally located nuclei
They have large, very long, unbranched, cylindrical fibers
Skeletal muscle has multiple subsarcolemmal nuclei
It exhibits strong, quick, intermittent contractions
Skeletal muscle is voluntary and controlled by the somatic nervous system
Skeletal muscle can hypertrophy by growth of new myofibrils increasing the diameter of the muscle fibers
Skeletal muscle cells contain ordered, arranged contractile sarcomeres forming cross-striations
Two types of skeletal muscle fibers: Type I and Type II

Type I Muscle Fibers (Slow Oxidative)

Rich capillary supply
Numerous mitochondria
Aerobic respiration
High myoglobin content (red fibers)
Less prone to fatigue
Do not produce high tension
Function: maintaining posture, stabilizing bones, and joints

Type II Muscle Fibers (Fast Oxidative/Intermediate)

Produce ATP relatively quickly
Produce high amounts of tension
High amount of mitochondria
Aerobic respiration
Myoglobin content less than Type I
Less prone to fatigue
Function: walking

Type IIb/IIx Muscle Fibers (Fast Glycolytic)

Anaerobic glycolysis
Less mitochondria (white fibers)
Less myoglobin
Rapid, forceful contractions
Quick, powerful movements
Prone to fatigue
Function: weight lifting

Sarcomere

I-band: actin filaments
A-band: myosin filaments, may overlap with actin filaments
H-band: zone of myosin filaments within the A-band
Z-line: zone of apposition of actin filaments belonging to neighboring sarcomeres (mediated by alpha-actinin)
M-line: band of connections between myosin filaments (mediated by proteins, e.g., creatine phosphate myomesin, M-protein).
T-tubule
Sarcoplasmic reticulum
Triad
External lamina

Smooth Muscle

Found in walls of hollow viscera and blood vessels (erector pili)
Small, spindle-shaped fibers (30-200 µm in relaxed state)
No striations
Single central nucleus
Weak, slow rhythmic contractions
Controlled by the autonomic nervous system
Mode of contraction: Ca release initiates a cascade that leads to sliding filaments, requiring calmodulin, and cAMP
Progesterone relaxes smooth muscles

Bone

Bone is a hard, rigid connective tissue, with an extracellular matrix impregnated with inorganic salts (e.g., calcium phosphate, carbonate).
Features: sclerous connective tissue, specialized in providing support due to infiltration with inorganic salts. It is characterized by rigidity, hardness, and power of regeneration and repair. It constantly undergoes remodeling to adapt to changing physical, biochemical, and hormonal influences
Functions: support, protection, movement, mineral storage, hematopoiesis.
Two types of bone: compact and spongy.
The structural unit of compact bone is called an osteon or haversian system; it's a cylinder with longitudinal orientation and 5-20 concentrically arranged lamellae. Lamellae have a crisscross pattern.
Spongy (trabecular) bone is a lattice-like network structure with trabeculae (plates) made of lamellae arranged in response to stress (Wolff's law).

Bone Cells

Osteoblasts: responsible for forming new bone. They synthesize and secrete collagen matrix and calcium salts
Osteocytes: primary cell of mature bone tissue, maintaining bone tissue. They lack mitotic activity and communicate via cytoplasmic processes extending through canaliculi
Osteogenic cells: mesenchymal stem cell line, source and precursors for osteoblasts.
Osteoclasts: responsible for bone resorption. They are multinucleated cells that originate from monocytes and macrophages

Bone Matrix

The extracellular matrix comprises the non-cellular component of bone tissue. It is highly specialized and contains collagen and associated proteins along with mineralized components, particularly calcium hydroxyapatite crystals organized into thin layers known as lamellae.

Bone Health and Diseases

Essential nutrients for bone health: calcium, Vitamin D, Vitamin K, magnesium, fluoride, omega-3 fatty acids.
Diseases related to skeletal system:
- Osteoporosis
- Rickets
- Osteomalacia
- Paget's Disease
- Rheumatoid arthritis

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Description

This quiz covers the fundamental aspects of muscle tissue, focusing on its origins, types, and structures. It also delves into skeletal muscle characteristics, including its cellular makeup and contraction mechanisms. Test your knowledge on the different muscle tissues and their functions.