Lecture 2: Joints and Muscle-Nervous Tissue

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synarthroses

immovable joints

amphiarthrosis

partially movable joints

diarthrosis

movable joints (uniaxial, biaxial, multiaxial)

fibrous joints

“at these joints, the adjacent bones are directly connected to each other by fibrous connective tissue, and thus the bones do not have a joint cavity between them”

1. sutures

2. gomphosis

3. syndesmosis

sutures

fibrous connective tissue that joins two bones of the skull

• synarthroses

gomphosis

fibrous connective tissue joins bones like a peg and socket (tooth in socket)

• synarthroses

syndesmosis

two bones joined by wide sheet of connective tissue

• amphiarthrosis

• ie: interosseous membrane between ulna and radius

cartilaginous joints

1. synchondrosis

2. symphysis

synchondrosis

hyaline cartilage directly connects two bones

• synarthrosis

• ie: epiphysial plate and first sternocostal joint

symphysis

pad of fibrocartilage connects two bones

• amphiarthroses

• ie: intervertebral disc

synovial joints

freely movable joints

• components:

  • articular surfaces

  • joint capsule

  • joint cavity

  • synovial fluid

  • ligament

articular surfaces

bone ends covered by hyaline (articular) cartilage

joint capsule

outer fibrous layer and inner synovial membrane

joint cavity

potential space enclosed by capsule

synovial membrane

specialized layer of connective tissue that lines the inner cavities of freely movable joints

• encase your joints in a layer of synovial fluid

synovial fluid

fills joint cavity, lubricates articular surfaces

ligaments (synovial joints)

reinforce joint capsule, connect bone to bone

specialized structures of synovial joints

1. bursa

2. tendon sheath

3. articular disc

bursa

fluid-filled sac reducing friction between bone and soft tissue

• ie: glenohumeral joint

tendon sheath

elongated sheath wrapping tendons, crossing joints

• ie: extensor pollicis sheaths

articular disc

fibrocartilage pad between articulating bones

• improves fit and distributes load

  • ie: meniscus in knee

diarthroses types and movments

joint structure determines range of motion at synovial joints

1. uniaxial

2. biaxial

3. triaxial

uniaxial joints

movement around one axis

• hinge

• pivot

• plane

hinge joint

flexion and extension

pivot joint

rotation

plane joints

gliding movement

biaxial

movement around 2 axes

1. condyloid

2. saddle

condyloid joints

flexion, extension, abduction, adduction, circumduction

saddle joints

flesion, extension, adduction, abduction, circumduction, medial and lateral rotation

muscle

specialized for contraction, generates force and drives movement of body and internal organs

muscle fiber

a single long, cylindrical muscle cell that can contract to produce movement

fascicle

a discrete bundle of skeletal muscle fibers grouped together in parallel and wrapped in a protective connective tissue layer called the perimysium

muscle contractility

cells contract and shorten; muscle cells are long in relaxed state

skeletal muscle

cells are long, multinucleated, and striated due to stacking of contractile proteins

• attach to bones via tendons

cardiac muscle

striated and contract synchronously as a unit via intercalated discs

• only in the heart

smooth muscle

cells are shorter and contract smoothly and sustained, no visible striations

• form sheets within organs and blood vessels

muscle organization

1. muscle fibers (cells) wrapped in endomysium → bundled to form fascicles

2. fascicles wrapped in perimysium → bundled with neurovascular structures to form skeletal muscle

3. skeletal muscle wrapped in epimysium and deep fascia → attaches to bone via tendon

muscle morphologies

fiber arrangement determines force and range of motion

• parallel, pennate, convergent, circular, digastric, tendinous intersections

tendinous intersections

fibrous transverse bands that segment the muscle longitudinally

• composed of dense connective tissue

parallel

fibers run along long axis

• max range of motion, less force

• fusiform (biceps brachii) = spindle-shaped

• thin parallel (sartorius) = thin parallel

• flat parallel with aponeurosis (external oblique): broad, flat sheet

• quadrate (rectus abdominus) = square or rectangular

pennate

feathered muscle fibers attach at angles to tendon

• more force, less range

• unipennate (extensor digitorum longus) = one side of tendon

• bipennate (rectus femoris) = both sides of tendon

• multipennate (deltoid) = multiple tendon branches

convergent

fan-shaped; fibers converge on a single tendon

• directs force to single attachment point (ie: pectoralis major)

circular

concentric ring fibers

• control opening/closing of passages (orbicularis oculi)

digastric

two bellies joined by intermediate tendon

• pulls in two directions simultaneously (omohyoid)

tendinous intersections

segment muscle into compartments for finer control

• ie: rectus abdominous

nerve

A bundle of fibers that receives and sends messages between the body and the brain

• the messages are sent by chemical and electrical changes in the fibers’ cells

neurons

primary cell type in CNS

• transmit electrical impulses and release biochemical signals at synapses

soma

cell body of neuron

• contains nucleus and cytoplasm, located in brain/spinal cord gray matter

dendrites

receive information

axon

conveys information, may be insulated in myelin

• bundles form white matter

synapses

connections between axons and dendrites of separate neurons

glia

non-neuronal cells

• astrocytes, oligodendrocytes, microglia, ependymal cells

astroctyes

blood-brain barrier

• metabolic support, healing

oligodendrocytes

myelinate (insulate) axons in CNS for fast propagation of impulses

microglia

resident immune cells

• phagocytize debris

ependymal cells

line ventricles

• produce cerebrospinal fluid

somatosensory neurons

convey sensory input to the CNS

• soma contains nucleus and cytoplasm

• axon is T-shaped with pseudounipolar morphology → one branch to periphery and one branch to CNS

PNS glia

1. satellite glia

2. schwann cells

satellite glia

metabolic support, neuronal impulse regulation, neuronal development

• located in peripheral ganglia surrounding neuron somata

schwann cells

insulate axons through myelination, aid in axon regeneration after injury

• located in peripheral nerves

organization of peripheral nerves

• axons wrapped in myelin and schwann cells → bundle in endoneurium to form fascicles

• fascicles wrapped in perineurium → bundled with vasculature and wrapped in epineurium to form a nerve

endoneurium

the fibrous tissue that surrounds myelinated and unmyelinated axons in the peripheral nerves (a connective tissue sheath called surrounds each nerve)

• consists mainly of collagen fibers

• plays a role in protecting and repairing injured axons

perineurium

in PNS - thin layer of connective tissue that surrounds an individual nerve fascicle, which is a group of neuronal axons

• encloses endoneurium

epineurium

the outermost layer of a peripheral nerve and is the strongest of all the connective tissue layers of the nerve

• surrounds each individual nerve fiber in PNS