joints/cartilage
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Questions and Answers

what are the 2 layers that comprise of the articular capsule that surrounds and encloses the synovial joint

outer layer (fibrous capsule) has dense, fibrous connective tissue attached to periosteum of articulating bones its flexibility permits movement at the joint whereas its strength resists dislocation

synovial membrane-inner layer has loose connective tissue inner surface, rich supply of blood capillaries lines entire joint cavity except articular cartilages and articular disc (if present)

give description and function of capsule in synovial joint

desc cartilage sac composed of two layers- outer fibrous layer and inner membrane

fn surrounds and encloses the joint

Fibrous capsule in synovial joint: desc and fn:

desc Dense fibrous connective tissue attached to the periosteum of the articulating bones.

fn Flexibility permits movement and strength; prevents dislocation.

synovial membrane: description and function

<p>desc: loose connective tissue inside fibrous capsule, well-supplied with BV</p> <p>fn: secrete synovial fluid into synovial cavity</p> Signup and view all the answers

fn and desc of synovial fluid

<p>desc: similar in appearance and consistency to egg white forms a thin film over surfaces in capsule contains phagocytic cells</p> <p>fn: lubricate joint provide nourishment for cells of articular cartilage and removes microbes and debris</p> Signup and view all the answers

articular cartilage desc and fn:

<p>desc smooth tough cartilage that covers articulating surfaces of the joint</p> <p>fn provide smooth surfaces that have little friction</p> Signup and view all the answers

desc and fn of articular discs

<p>desc fibrocartilage menisci extend inwards from articular cartilage</p> <p>fn divide synovial cavity into 2 directing synovial fluid to areas of greatest friction</p> Signup and view all the answers

desc and fn of bursae

<p>desc small sacs of synovial fluid</p> <p>fn reduce friction between bones and ligaments or tendons or btwn bone and skin</p> Signup and view all the answers

accessory ligaments desc and fn

<p>desc extra ligaments in joints</p> <p>fn hold bones tgt, particularly during extended movement</p> Signup and view all the answers

what three factors keep articular surfaces of synovial joints in contact with each other

<p>fit of articulating bones</p> <p>strength of joint ligaments</p> <p>tension provided by muscles around the joint</p> Signup and view all the answers

eg of synovial joint: ball and socket joint

<p>spherical head of one bone fits into cup like cavity of another</p> <p>e.g. head of humerus fits into depression of scapula head of femur articulates with pelvis</p> Signup and view all the answers

hinge joint = synovial joint

<p>allow movement in one plane only, like a hinge door convex surface of one bone fits into concave surface of another</p> <p>e.g. elbow and knee</p> Signup and view all the answers

pivot joint = synovial joint

<p>rounded end of one bone articulates with a ring, formed partly by bone and partly by a ligament</p> <p>e.g. radius and ulna</p> Signup and view all the answers

gliding joint = synovial joint

<p>allow movement in any direction restricted only by ligaments or bony processes surrounding joint</p> <p>e.g. scapula and clavicle btwn carpal bones btwn tarsal bones btwn sternum and clavicle</p> Signup and view all the answers

saddle joint = synovial joint

<p>2 bones forming the joint are both saddle-shaped – concave in one direction and convex in the other; they fit together in such a way that they allow both side-to-side and back-and-forth movements.</p> <p>e.g. metacarpal bone of thumb</p> Signup and view all the answers

condyloid (ellipsoid) joint = synovial joint

<p>Have one surface of bone slightly convex that fits into a slightly concave depression in another bone; they allow movement in 2 directions</p> <p>e.g. btwn metacarpal bones and phalanges of fingers btwn metatarsal bones and phalanges of toes</p> Signup and view all the answers

the five movements of a joint

<p>flexion (bending) decrease angle between articulating bones</p> <p>extension (straightening) increase angle between articulating bones</p> <p>abduction movement away from midline of body</p> <p>adduction movement toward midline of body</p> <p>rotation movement of bone around its long axis</p> Signup and view all the answers

joints can be classified by their structure and the amount of movement they allow. what are the 3 structures, and how are they classified?

<p>fibrous no joint cavity no movement</p> <p>cartilaginous no joint cavity none/slight movement</p> <p>synovial: there is a joint cavity freely moveable</p> Signup and view all the answers

structure, characteristic and location of hyaline cartilage

<p>structure contains many packed collagen fibres in matrix</p> <p>chara great strength toughness flexibility</p> <p>location rings of bronchi and trachea and on articulating bone surfaces</p> Signup and view all the answers

structure chara and location of elastic cartilage

<p>structure elastic fibres collagen fibres aren't so tightly packed</p> <p>chara: flexible elastic support</p> <p>location: external ear epiglottis</p> Signup and view all the answers

fibrocartilage structure characteristics and location

<p>structure thick coarse collagen fibres in bundles</p> <p>chara strength and toughness but can be slightly compressed ideal for supporting weight</p> <p>location invertebral discs articular cartilage of knee joint between pubic bones joining 2 sides of pelvis</p> Signup and view all the answers

macroscopic structure of cartilage

<p>numerous fibres made of collagen</p> <p>collagen is embedded in a firm matrix of chondrin (protein-carbohydrate complex)</p> <p>firm matrix enables cartilage to function as structural support</p> <p>presence of fibres gives cartilage a certain amount of flexibility</p> Signup and view all the answers

microscopic structure of cartilage

<p>firm matrix which has spaces for collagen fibres and cartilage cells (chondroblasts)</p> <p>chondroblasts produce matrix and gradually become surrounded by it until they're trapped in small spaces (lacunae)</p> <p>once trapped in lacunae, chondroblasts are considered to be mature and are known as chondrocytes</p> <p>collagen fibres in matrix range in thickness, the variation in fibrous structure classifies cartilage into 3 types: hyaline cartilage elastic cartilage fibrocartilage</p> Signup and view all the answers

whats axial skeleton

<p>bones lie along central axis of body provide main support for erect posture protects CNS and thoracic organs</p> <p>bones include skull, vertebral column, ribs and sternum</p> Signup and view all the answers

appendicular skeleton

<p>bones making up the upper and lower limbs and the bones of the pectoral (shoulder) and pelvic (hips) girdles.</p> Signup and view all the answers

what a long bone consists of, a description

<p>shaft (diaphysis): main portion of bone</p> <p>ends (epiphyses): enlarged ends of bone; a thin layer of cartilage, articular cartilage covers each epiphyses</p> <p>diaphysis is a hollow cylinder of compact bone surrounding a cavity. this cavity is used as far storage site and is often called the yellow bone marrow cavity</p> <p>epiphyses have compact bone on outside but spongy (or cancellous) bone in central regions. cancellous bone is more porous and contains many spaces filled with marrow</p> <p>outer surface of bone = dense white fibrous covering (periosteum)</p> Signup and view all the answers

• On the outer surface of the bone is a dense white fibrous covering, the ______.

<p>periosteum</p> Signup and view all the answers

what makes up the main portion of the bone?

<p>diaphysis</p> Signup and view all the answers

what type of cartilage covers each epiphysis

<p>articular cartilage</p> Signup and view all the answers

what is the cavity in the diaphysis often called? (this cavity is used as a fat storage site)

<p>yellow bone marrow cavity</p> Signup and view all the answers

cancellous bone is more porous and contains many spaces filled with marrow.

Signup and view all the answers

Study Notes

Articular Capsule

  • Composed of two layers: the fibrous capsule and the synovial membrane.

Fibrous Capsule

  • Description: Dense connective tissue forming a strong outer layer, providing stability while allowing mobility.
  • Function: Encloses the joint, prevents dislocation, and protects underlying structures.

Synovial Membrane

  • Description: A thin layer of connective tissue lining the joint cavity and producing synovial fluid.
  • Function: Secretes synovial fluid for lubrication, nourishment, and waste removal.

Synovial Fluid

  • Function: Reduces friction between articular cartilage surfaces, cushions joints, and supplies nutrients to cartilage.
  • Description: Viscous, clear fluid found within the synovial cavity.

Articular Cartilage

  • Description: Smooth, white connective tissue covering the ends of bones at joints.
  • Function: Reduces friction, absorbs shock, and distributes load during movement.

Articular Discs

  • Description: Fibrocartilaginous structures located between articulating surfaces of some joints (e.g., knee).
  • Function: Improve fit between bones, absorb shock, and stabilize joints.

Bursae

  • Description: Fluid-filled sacs located between bone and soft tissues (muscles, tendons).
  • Function: Reduce friction and cushion pressure points in joints.

Accessory Ligaments

  • Description: Strong bands of connective tissue outside the articular capsule.
  • Function: Provide additional stability to the joint by limiting the range of motion.

Factors Maintaining Contact in Synovial Joints

  • Ligaments provide stability by connecting bone to bone.
  • Muscles and tendons exert force on joints, ensuring alignment.
  • Joint surfaces conform to each other, aiding in stability.

Examples of Synovial Joints

  • Ball-and-socket joint: Allows for circular movement (e.g., shoulder).
  • Hinge joint: Enables bending and straightening (e.g., elbow).
  • Pivot joint: Permits rotation around a single axis (e.g., neck).
  • Gliding joint: Allows for sliding movements between flat surfaces (e.g., wrist).
  • Saddle joint: Provides a wide range of movement with opposing surfaces (e.g., thumb).
  • Condyloid (ellipsoid) joint: Allows for movement but limits rotation (e.g., wrist).

Movements of a Joint

  • Flexion: Decreasing the angle between two body parts.
  • Extension: Increasing the angle, returning to the anatomical position.
  • Abduction: Movement away from the midline of the body.
  • Adduction: Movement towards the midline of the body.
  • Rotation: Movement around a central axis.

Classification of Joints by Structure

  • Three types:
    • Fibrous joints: Connected by dense connective tissue, immovable (e.g., sutures in the skull).
    • Cartilaginous joints: Bones connected by cartilage, partially movable (e.g., ribs to sternum).
    • Synovial joints: Movable joints with a fluid-filled cavity.

Cartilage Characteristics

  • Hyaline Cartilage

    • Structure: Glassy appearance, resilient, and flexible.
    • Location: Covers joint surfaces, forms costal cartilages, and tracheal rings.
  • Elastic Cartilage

    • Structure: Similar to hyaline but with more elastic fibers.
    • Location: Found in the ear and epiglottis.
  • Fibrocartilage

    • Structure: Tougher and denser with thick bundles of collagen fibers.
    • Location: In intervertebral discs, menisci of the knee, and pubic symphysis.

Structure of Cartilage

  • Macroscopic: Smooth, shiny surfaces providing load distribution and resistance to compressive forces.
  • Microscopic: Composed of chondrocytes in lacunae, surrounded by a matrix containing collagen and proteoglycans.

Skeleton Overview

  • Axial Skeleton: Comprises the skull, vertebral column, and rib cage; supports the body's central axis.
  • Appendicular Skeleton: Includes limb bones and girdles; facilitates movement and interaction with the environment.

Long Bone Composition

  • Consists of a diaphysis (shaft), epiphyses (ends), and a medullary cavity filled with bone marrow.
  • Provides structural support, facilitates movement, and stores minerals.

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