~L5-6: Skeletomuscular Structure and Functions

The five main anatomical components of the musculoskeletal system:

1. Muscle

2. Bone

3. Tendons

4. Ligaments

5. Cartilage

• Ligaments and tendons are examples of _____________ tissue while

• Cartilage and bones are an example of ________________ tissue

dense regular connective - supportive connective

Supportive connective tissues have a ____________ matrix.

dense, solid

Cartilage is vascular/avascular and has ________ residing in lacunae which produce _________

avascular - chondrocytes - collagen + ECF

Cartilage surface is covered by a ______________, which is a __________________ tissue

perichondrium - dense fibrous connective

Collagen’s three subtypes:

1. __________: proteoglycans

   1. e.g. _____________

2. __________: proteoglycans + elastin

   1. e.g. _____________

3. __________: proteoglycans + collagen

   1. e.g. _____________

1. hyaline - joints

2. elastic - ear

3. Fibrocartilage - intervertebral discs

Bone tissue is vascular/avascular and filled with _____________. They have lacunae which house ___________.

vascular - bone marrow - osteocytes

Compact bone is organized into _____________ separated by layers of __________. It _______ force.

concentric rings - matrix - resists

Spongy bone is organized into ___________ within ___________. It ________ force

trabeculae - bone marrow - distributes

Bone tissue cell that produces other bone cells + location

osteogenic cells - endosteum

Bone cells that maintain bone matrix:

Osteocytes - moved down form osteoblasts

Bone cells that produce bone matrix + location

Osteoblasts - periosteum

Bone cell that dissolves bone matrix + location

Osteoclasts - medullary cavity

Why is it important that bone can be remodeled by cellular activity?

mineral reservoir: t can store or release minerals as needed

When calcium levels are high, __________ cells will __________.

If they are low, ______ cells will _____________.

• High: osteoblasts - make new bone matrix

• Low: osteoclasts - break down bone to release calcium and phosphate ions

Cartilage can grow through ____________ as well as __________ during childhood.

differentiation - cell division

Interstitial cartilage growth involves the ____________ of ___________ cells. Cells are pushed apart by: ___________.

proliferation - chondrocyte - new matrix secreted

_________ cartilage growth is growth by differentiation:

• _______ to ___________

• ___________ secrete ___________

• ___________ to _____________

appositional

• stem/mesenchymal cells - chondroblasts

• chondroblasts - new matrix

• chondroblasts - chondrocytes

Endochondral growth is the growth of ________ by the _________ of _________ . It only occurs during childhood and begins as __________ in utero.

bone - ossification - cartilage - hyalin cartilage

• Endochondral growth starts with ossification at the _________ then the _________.

• ___________ grow by _______ _______ until they ossify at puberty.

• shaft - epiphyses

• epiphysial plates - interstitial division

• Bones lengthen at the ____________. Chondrocytes divide then _______, causing the matrix to ________.

• Then _______ will secrete _________ and _________ will occur.

• epiphyseal - die - calcify

• osteoblasts - bone matrix - ossification

Intramembranous ossification is the direct conversion of __________ _________ cells in _______ ______ connective tissue into __________.

embryonic mesenchymal - dense proper - osteoblasts

_______ and _______ bones are examples of bones made through intramembranous bones.

dermal - sesamoid

Bone can grow by _______ growth, as well as __________ growth & __________ during embryonic development and childhood.

appositional - endochondral - intramembranous ossification

• The diameter of a bone increases with ___________ growth at the inner layer of the ___________ with the activity of ___________.

• As the bone diameter increases, (cell + activity), will cause the _________ to expand.

• appositional - pericardium - osteoblasts

• osteoclasts break down bone matrix - medullary cavity

Synovial joints are part of the __________ functional category.

Diarthrosis (free movement)

Synovial joints have _______ cartilage, a sub-type of ________ cartilage.

articular - hyaline

Bone repairs itself through ____________ of cells, starting with ________ → __________ → _________. Calluses are formed by __________

extra proliferation

cartilage → spongy bone → compact bone

secreting chondrocytes

Cartilage can only repair itself through __________ only for _____ and ______ cartilage and not ________ cartilage because __________.

appositional growth - fibro/elastic cartilage - articular - it has no perichondrium (contains stem cells)

Osteoarthritis is caused by damage to the ______________. This increases _________ which leads to inflammation and more ______________

articular cartilage - friction - pressure on remaining cartilage.

The two categories and three subtypes of muscle tissue:

1. Striated

   1. Skeletal

   2. Cardiac

2. Smooth

Which type of muscles are striated?

Which are multinucleated?

• Striated: skeletal, cardiac

• Multinucleated: skeletal

All muscle tissue is specialized for _______ and producing ___________ ________.

contraction - mechanical force

Muscles are connected to the skeletal system via:

• ___________ —→ narrow and rounded

• ___________ —→ broad and flat

• Tendons

• Aponeuroses

Skeletal Muscles are organized into _____________

layers of fasciae

A singular muscle consists of many bundles of ________ called _________ which are surrounded by a __________.

muscle fibres - fascicles - perimysium

A singular myofiber within a _______ consists of many ________ wrapped into an __________.

fascicle - myofibrils (+ other organelles) - endomysium

An endomysium (found around _________) will contain:

• _______________

• _______________

• _______________ cells

  • _________ for muscle tissue

myofiber

• motor neuron axon

• capillaries

• Myosatellite cells

  • Stem cells

Myofibers Main Organelles:

• M____________

• S____________

• S____________

• S____________

• ____________

• Sarcolemma

• Sarcoplasm

• Sarcoplasmic Reticulum

• T-Tubules (Transverse Tubules)

• Myofibrils

Sarcoplasmic Reticulum function + position

Store and release calcium - surrounds myofibril

T-Tubule position

Right angle to the cell surface, continuous with the sarcolemma

Myofibers are produced by the fusion of many _________, forming a single, _______ cell

myoblasts - multinucleated

Adult tissue repair on myofibers is done through the _________ of _________ cells.

proliferation - myosatellite

• Contraction: Myofibers/myofibrils becoming __________ and ___________

• Excitation: The __________ generating an electrical signal before ___________.

• shorter - producing tension

• sarcolemma - contraction

A myofiber will have one NMJ which consists of:

• The __________ of a motor neuron

• The ____________ and _____________ of the myofiber.

• axon terminal

• synaptic cleft - motor end plate

Combination of a motor neuron and muscle cells:

motor unit

Excitation of a muscle cell occurs at the _______:

1. _______ receives a command from the nervous system.

2. Activation will excite the myofibre

NMJ

1. motor neuron

Charged ions will move not only according to diffusive forces but __________ forces as well

electromotive

V_m is the _______________. An excited cell will have a __________ V_m than at rest.

Transmembrane potential - less negative

Excitable cells will alter their Vm when stimulated to ___________________.

send/receive signals (potentials)

V_m is measured in _____ and take place within _________

mV - milliseconds

_________ potentials occur in the _________ and when summation reaches a threshold, a __________ potential occurs in the __________.

Graded - cell body - action - axon

Vm signals, or _________ potentials are generated by ______ rapidly crossing the __________ through _________.

Membrane - ions - plasma membrane - ion channels

The four categories of ion channel gating:

• Leak Channels (ungated)

• Gated:

  • Ligand Gating

  • Voltage gating

  • Mechanical Gating

Motor neurons release the neurotransmitter _____________ which opens _______ gated ion channels that allow ____ into the __________.

Acetylcholine - ligand - Na+ - Myofibre

Myofibre excitation at the _______:

1. ______ potential arrives at the ______ neuron’s __________

2. _______ is released into the __________by ___________.

3. Neurotransmitter binds to __________

4. Inrush of ___ ions generates an _______ potential in the ____________

NMJ:

1. Action - motor - axon terminal

2. Acetylcholine - synaptic cleft - exocytosis

3. ACh receptors on ligand-gated channels

4. Na+ - action - sarcolemma

Excitation propagates through the myofibre’s ______ from the ____ by opening and closing _______-gated ___ ion channels

sarcolemma - NMJ - voltage - Na+

______ propagate the action potential to the ___________, triggering _____ release with the help of ______ and ______ membrane proteins.

T-tubules - sarcolemma - Ca2+ - DHPR - RYR

The ________ potential generated at the neuromuscular junction triggers the opening of voltage-gated channels which initiate an ________ potential in the muscle sarcolemma.

graded - action

Acetylcholine released at the neuromuscular junction triggers the opening of ion channels that change the ________ potential of the _________, causing a _________potential.

membrane - myofiber - graded