Skeletal Muscle Tissue: Characteristics & Development

Skeletal Muscle Tissue

• Discussed: skeletal, smooth, and cardiac muscle tissue
• Skeletal muscle characteristics include parallel striations, uniformity, and multiple nuclei peripherally located due to myoblast fusion during development.
• Striated appearance caused by myofilament arrangement
• Myofilaments consist of actin and myosin proteins

Myogenic Origins

• Muscle cells are derived from stem cells and have myogenic origins
• Long muscle cells result from the fusion of numerous myoblasts, while shorter muscles develop from unfused, maturing myoblasts

Smooth Muscles

• Smooth muscles support the lining of organs and other bodily structures
• They appear least organized and consist of short cells with nuclei that are not perfectly parallel

Skeletal Muscle Development

• Myoblast fusion is significant during development to form mature cells

Connective Tissue

• Muscles contain bundles of fascicles and fibers, protected by linings
• Connective tissue layers between muscles is the Endomecium

Sarcomeres

• Functional units within striations
• The striation is typically parallel to the muscle's function
• Sarcomeres shorten to enable bodily movement

Muscle Arrangement

• Includes up and down arrangement
• Obliques have horizontal arrangement
• Depend on how myosin and actin shortens muscles during contraction.

Osseous (Bone) Tissue

• Bones have a sandwich-like appearance with compact bone layers

Periosteum

• Connective tissue layer providing membranous protection to bones
• Bones have protective connective tissue called periosteum

Compact Bone

• Compact bone's function resists compressive forces due to densely packed matrix and osteocytes

Spongy Bone

• Spongy bone appearance resembles a lettuce-like structure.
• Provides support by distributing weight

Bone Structure

• Proximal and distal ends of the bone help reveal structures
• Red bone marrow will be discussed

Articular Cartilages

• Act as a shock absorber and for joining bone

Spongy Bone Location

• In the top proximal part of the bone

Red Bone Marrow

• The spaces in the trabecular mesh-like contains red bone marrow

Compact Bone Location

• Compact bone makes up the majority of long bones

Bone Marrow Types

• Yellow bone marrow has bone marrow

Bone Articulation

• Bones are usually wider where they articulate with another bone
• These wider parts are called epiphysis lines

Epiphysis/Growth Line

• Epiphysis areas are important for bone growth, so that is when the bones are growing towards adolescence

Epiphysial Growth Plate

• During growth, the epiphysial growth plate is cartilage tissue that eventually ossified once the bone matures

Metaphysis

• The area of bone connected between the epiphysis
• This has to do with length and growth

Metaphysis Bone Growth

• Metaphysis develops new osseous cells that help push up towards the epiphysial line
• Connected to remodeling

Bone Growth Areas

• The metaphysis is responsible for growth, leading up to adolescence
• It lies between the wide epiphysis and narrow diaphysis

Red Bone Marrow

• Hemocoiesis (red blood cell formation) occurs here

209 Course

• Yellow fat deposits in marrow are related to survival and nutrients

Endosteum

• The inner tissue lining of compact bone
• Located around spongy bone layers

Nutrient Artery

• Nourishes living tissue
• Osseous tissue is alive

Periosteum, Compact Bone and Spongy Bone

• Medullary cavity filled with yellow bone marrow

Osteons

• Connective tissues layering protections
• Found in rings within the compact bone
• Concentric rings called osteons

Central Canal

• Blood and lymphatic systems are vital for protection

Osteocytes

• The osteocytes are matured cells in concentrated circuits
• Osteo cells matrix build from osteycytes

Interstitial Lamella

• The place between cell/vessels

Bone Growth Reminders

• Periosteum, compact bone, spongy bone can exist
• Trabeculae and medullary cavity also exist

Osteons Functional

• Osteons function from concentric lamellae

Epiphysis Areas

• Look at the epiphysis metaphysis area to see structure
• Trabeculae or ostiums are visible

Highlighted Section

• Bony matrix is calcium and phospates

Osteocytes

• Live cells that maintain or detroys the bony matrix
• Osteoclast: Breaks down bone matrix. Requires a specific thyroid gland

Osteogenic Cells

• Eventually mature

Breaking down Matrix

• The spongy side will break everything down

Matrix Composition

• The new matrix is composed of calcium and phosphates that will be deposited into bone.

Bone Remodelling

• Bone remodelling continues, but also strains with new cells
• • *The rate depends on level of strain
• Breaking down osseous cells that lead to OSteoclasts actions

Difference between Osteocyte and Osteoblast

• An osteocyte is a mature cell, but also contains osteblasts

Bone Cells

• Cells die when they obtain calcium
• Calcium source keeps maintenance in the bones

Intramembranous growth.

• The other types are the types are types
• Happens early and continues with the process

Intramembranous and Endochondral Growth Differences

• One is flat bones and the other is long

Bone Remodeling

• Maintained by osteoclasts which breaks down new cells

Con Cartilage

• 1st develops from cells

Muscle Contraction

• Calcium that helps talk for osteoclasts
• Homeosta Muscles balance with 2 minutes

Hypercalcemia

• Bones can fix elevated levels

Increased increase (osteoclast)

• Osteoclast activity in the bones (activity)

Calciumin Reabsorption

• Decreases calcium levels

Parathyroid glands

• In the anterior side of glands
• Connect calcium can bind and preventing hormones

Parathyroid Hormone

• Controls their realase

The Calcium Loop

• Releasing parathyroid hormone
• It really supports everything

Muscle Tissues

• Characteristics and their structures
• Types in skeletal muscles
• Straitions contain myosin and actin proteins

Muscle and Organs

epimysium - outer layer of connective tissue Perimysium bundles skeletal muscle fibers into fascicles. Surrounds the entire muscle fibre and around each myofibril myofilaments: actin and myosin largest to smallest:

• actin—>myosin—>myofibril —> muscle fiber —> muscle fascicle-->skeletal muscle

Connective Tissues and Muscles

smallest to largest:

skeletal muscle->muscle fascicle->muscle fiber—> myofibril->myosin_>actin

Explore the characteristics of skeletal muscle, including striations, nuclei placement, and myofilament composition. Understand the myogenic origins of muscle cells and their development through myoblast fusion. Also, a short overview of smooth muscles.