Bones and joints Flashcards

Question

Four main types of bone cells

Answer 1

osteogenic cells, osteoblasts, osteocytes, and osteoclasts. These cells help with the production and maintenance of the mineral extracellular matrix that surrounds them.

Answer 2

Compact bone and spongy bone. Approximately 80% of the skeleton is formed by compact bone, with the remaining 20% formed by spongy bone.

Answer 3

The bones of the skeletal system are intimately linked with a specialized type of connective tissue known as cartilage. It is made up of a dense network of collagen or elastic fibers and the associated matrix materials which provide strength and resilience. Cartilage extracellular matrix is deposited by chondroblasts, which mature into chondrocytes and sit in spaces within the extracellular matrix called lacunae. A sheet of connective tissue known as the perichondrium covers the surface of most cartilage throughout the body. Indeed, during embryological development the whole skeleton is initially comprised of cartilage, which gradually undergoes ossification (where it is converted into bone). Even the bones of adults, especially where they interact with other bones at joints, are often capped by cartilage. Different types of cartilage including hyaline cartilage, fibrocartilage, and elastic cartilage are found at different joints and each has a specific structure and function.

Answer 4

Hyaline cartilage is composed of fine collagen fibers bound together by a resilient, gel-like matrix material. It is usually covered with perichondrium. Chondrocytes within lacunae are found throughout. Hyaline cartilage is the weakest but the most abundant cartilage in the body, providing flexibility and support, reducing friction, and absorbing shock. Hyaline cartilage forms a temporary skeleton in the fetus, which is then gradually ossified during childhood. It also forms the epiphyseal plates of growing long bones, covers the articular surfaces of joints, and provides support to respiratory passages.

Answer 5

Fibrocartilage is made up of thick bundles of collagen fibers, interspersed with chondrocytes in their lacunae. It is the strongest cartilage in the body, providing strength and rigidity. Fibrocartilage is a major constituent of intervertebral discs, tendon attachment to bones, and the junctions between flat bones of the pelvis. It lacks a perichondrium.

Answer 6

Elastic cartilage is made up of a thread-like network of elastic and collagen fibers, interspersed with chondrocytes in their lacunae. It is covered by perichondrium. Elastic cartilage is strong and elastic, providing and maintaining the shape of various structures. Elastic cartilage forms the auricle of the ear, the walls of the external auditory meatus and Eustachian tube (pharyngotympanic tube), and the epiglottis of the larynx.

Answer 7

Osteogenic (osteoprogenitor) cells are unspecialized mesenchymal cells (a tissue from which most connective tissue is derived). They are found predominantly alongside the membranes that surround the bones and the blood vessels in bone canals. These cells are the only bone cells to undergo cell division, with the resulting cells developing into bone producing cells (osteoblasts).

Answer 8

Osteoblasts are bone producing cells present in regions of bone formation, such as the surface of growing bones or areas undergoing active bone remodelling. They are basophilic, mononuclear, and roughly cuboidal in shape. The function of the osteoblast is to synthesize and secrete collagen fibers and other organic components. These are used to build the extracellular matrix of bone tissue and to initiate calcification. When osteoblasts surround themselves with extracellular matrix, they become trapped in their own secretions and eventually become osteocytes.

Answer 9

Osteocytes constitute the major cell type found in mature bone. They are derived from osteoblasts and are found within the matrix of the bone. Their function is to maintain the daily metabolism of bone tissue, which includes the exchange of nutrients and waste with the blood. Osteocytes have an ellipsoid cell body, few organelles, and are mononuclear. They also possess a number of fine, dendritic processes that emerge from the cell body and project into the matrix. This allows them to form gap junctions, enabling communication between neighboring osteocytes.

Answer 10

Osteoclasts are large cells containing approximately 15-20 nuclei. They are derived from the fusion of monocytes present within bone marrow or from other blood producing tissue. Osteoclasts lie in close contact with the bone surface in resorption bays called Howship's lacunae, and are mainly concentrated within the layer of connective tissue on the inside of the bone. Functionally, osteoclasts are responsible for the local removal of bone during bone growth and the subsequent remodeling of the bone surface. This process is termed resorption and is commonly seen in the normal development, maintenance, and repair of bone. Structurally, the edge of the cell that is closest to the bone has a highly infolded cell surface called a ruffled border. Here, powerful lysosomal enzymes and acids are released, and the digestion of the protein and mineral components of the extracellular matrix takes place.

Answer 11

Bone matrix contains both organic and inorganic components. The organic part of the bone matrix is composed of a material known as osteoid. This tissue is produced and secreted by osteoblasts, and is maintained by the osteocytes. Osteoid is made predominantly of type 1 collagen fibers, and a small proportion of ground substance, which contain chondroitin sulfate and osteocalcin. These organic components contribute to the overall flexibility and structure of the bone itself. Approximately fifty percent of bone is made up of an inorganic mineral called hydroxyapatite. This inorganic crystaline mineral is formed from mineral salts, such as calcium phosphate and calcium carbonate, which combine with additional mineral salts present in the extracellular matrix. A process called calcification, facilitated by osteoblasts, deposits these mineral salts into the microscopic spaces in the collagen framework of the matrix and crystallizes them to form hard tissue, providing rigidity and structure to bone. Bone tissue contains a number of spaces between its cells and extracellular matrix. These spaces are required for various functions: to store red bone marrow and to provide a pathway for blood vessels. The size and distribution of these spaces determine whether the bone tissue can be categorized as compact or spongy bone. Although the properties of compact and spongy bone are structurally and functionally different, the bone matrices present withinboth have a number of similar general features.

Answer 12

Lamellae are concentric rings of calcified extracellular matrix. All the collagen fibers in one lamella run in a single direction, but in the adjacent lamella, they run in an opposite direction. This allows the functional unit of the bone to withstand torsion pressures.

Answer 13

Lacunae are tiny cavities located between thelamellae that contain the spider-like osteocytes.

Answer 14

Hair-like canals called canaliculi, filled with extracellular fluid, radiate from the lacunae. Their purpose is to connect lacunae to each other, providing many routes for nutrients to reach the osteocytes and to remove their waste.

Answer 15

Compact (cortical) bone is the strongest form of bone tissue. It contains relatively few spaces and forms the tough outer layer of each bone. This bone tissue provides support and protection to the skeletal system, while also helping to reduce the stress placed on bone by weight and movement. Compact bone is much denser and harder than spongy bone and approximately 80% of the skeleton comprises compact bone. The structural and functional unit of compact bone is called an osteon or Haversian system. These repeated units are all aligned in the same direction and consist of a number of different structures.

Answer 16

Circumferential lamellae are rings of calcified extracellular bone matrix that line the inner and outer surfaces of compact bone.

Answer 17

The structural unit of compact bone is called an osteon or Haversian system. Each osteon is an elongated, cylindrical structure consisting of a number of concentric rings of lamellae surrounding a central canal. Osteons usually lie parallel to each other along the long axis of the bone.

Answer 18

Central canals, also known as Haversian canals, are channels that run through thecore ofeach osteon. These central canals run longitudinally through the bone and facilitate the passage of neurovascular structures, such as small blood vessels and nerve fibers.

Answer 19

Interstitial lamellae are areas of incomplete lamellae present in the areas between osteons. This lamellae is formed from old fragments of osteons that have been partly destroyed during bone resorption or growth.

Answer 20

Perforating canals, also known as Volkmann's canals, are transverse channels that lieat 90 degreesto the central canals and long axis of the bone. These channels serve to connect the blood and nerve supply of the periosteum with the neurovascular supply of the central canals and medullary cavity.

Answer 21

Spongy (trabecular) bone is much lighter than compact bone. It consists of branching and anastomosing bars and plates of osseous tissue. Spongy bone makes up the interior bone tissue of short, flat, and irregularly shaped bones, as well as the majority of epiphyses in long bones. Spongy bone can generally be found in bones that undergo a small amount of stress. In contrast to compact bone, spongy bone does not contain osteons, and the lamellae are arranged in an irregular lattice of thin columns called trabeculae. These trabeculae surround and support red bone marrow, which produces red blood cells through a process known as hemopoiesis.

Answer 22

Only a few cells thick, the trabeculae contain a number of irregularly arranged lamellae and osteocytes, interconnected by canaliculi to form a lattice of thin columns. The appearance of this lattice gives rise to the name of the spongy bone tissue. Although irregularly arranged, the trabeculae of spongy bone are oriented along a bone's lines of stress, thus helping to reduce stress on the bones as they move. Trabeculae have many macroscopic spaces, which make the bone much lighter in weight. In some bones, such as the hip bones, vertebrae, sternum, ribs, and ends of long bones, these spaces are filled with bone marrow, which contains a large number of small blood vessels. These vessels facilitate the exchange of nutrients with the osteocytes as well as the removal of waste.

Answer 23

Each bone of the skeletal system is classified as a discrete organ, due to the fact that it is constructed of several different types of tissue. These tissues include osseous tissue, cartilage, dense connective tissue, nervous tissue, hemopoietic tissue, and adipose tissue. Bone is a complex and dynamic tissue, continually being remodeled to provide new bone, while the old bone is removed. Specialized cells known as osteoblasts and osteoclasts undertake this process and are present within every bone tissue. Each of the 206 bones in the body varies in shape and function. Shape-wise, they can be classified as long, short, flat, irregular, or sesamoid. Although their shape and function may differ, most bones within a certain classification will have the same general structure.

Answer 24

Long bones are generally identified as being greater in length than in width. They are formed from a hollow, tubular shaft, called the diaphysis, which is expanded at either end to form articular heads, called the epiphyses. Long bones comprise of a dense layer of cortical bone, which lies around the periphery of the bone, and spongy bone, which is found in the epiphyses. The trabeculae within the epiphyses contain both red and yellow bone marrow. Red bone marrow is responsible for blood cell production, while fatty yellow bone marrow is present within the medullary cavity of the diaphysis. Long bones are located principally in the limbs of the appendicular skeleton and include the humerus, radius, ulna, metacarpals, phalanges, femur, tibia, fibula, and metatarsal bones.

Answer 25

The diaphysis is a long, cylindrical structure which forms the main shaft of a long bone. It is formed by a relatively thick layer of compact bone that overlies a thin layer of spongy bone. The central part of the diaphysis is hollowed to form the medullary or marrow cavity. There are two main types of bone marrow: red marrow, which comprises red blood cells, white blood cells, and platelets, and yellow marrow, which mainly comprises fatty, adipose cells. At birth, all marrow present within the long and flat bones is red, but as we age, bone marrow changes from red to yellow and fills the inside of the medullary cavity.

Answer 26

The epiphyses are the rounded parts located at the proximal and distal ends of a long bone. The interior of each epiphysis is filled with spongy trabecular bone containing red bone marrow. The exterior surface of the epiphyses is covered in compact bone in order to protect the fragile, spongy tissue below it.

Answer 27

The metaphyses are regions of bone found between the diaphysis and epiphyses of long bones. During the growth of a bone, a thin layer of hyaline cartilage known as the epiphyseal plate is formed between the diaphysis and epiphysis, which allows the shaft to grow in length. However, when growth stops during early adulthood, the cartilage in the epiphyseal plate is replaced with a bony structure called the epiphyseal line.

Answer 28

The periosteum is a fibrous membrane that covers the exterior of each bone, except where bones are covered by articular cartilage. It consists of two layers: an outer fibrous layer of dense, irregular connective tissue, and an inner, osteogenic layer that sits on the surface of bones and consists primarily of bone-producing osteoblasts and bone-destroying osteoclasts. The periosteum functions to help with fracture repair, to nourish and protect the bone, and to act as an attachment point for tendons and ligaments. The membrane is secured to the underlying bone by thick bundles of collagen fibers called perforating fibers, also known as Sharpey's fibers, which extend from the periosteum to the extracellular bone matrix. The periosteal layer has a rich supply of nerve fibers as well as blood and lymph vessels that enter the diaphysis from the surrounding areas, via various nutrient foramina.

Answer 29

Internal bone surfaces facing the medullary cavity are covered by a thin layer of cells and connective tissue called the endosteum. This membranous layer covers the trabeculae of spongy bone and also lines the canals that pass through the cortical bone. Like the periosteum, the endosteum has a rich neurovascular supply and contains both osteoblasts and osteoclasts.

Answer 30

Flat bones are formed of two thin plates of periosteum-covered compact bone, separated by a thin layer of endosteum-covered spongy bone. Bone marrow is still present between the trabeculae of the spongy bone, but not within the medullary cavity. As these bones are not cylindrical in shape, they do not have a shaft, medullary cavity, or epiphyses. In flat bones, the trabeculae sandwiched between compact bone are termed diploe. The slightly curved nature of most flat bones means that they are ideally shaped to provide a large amount of protection to the underlying soft tissue. Their large surface area also provides an extensive area for muscle attachment. Examples of flat bones include: the frontal, hip, lacrimal, nasal, occipital, parietal, ribs, scapula, sternum, and vomer bones.

Answer 31

Blood supply varies according to different types of bone. Osseous tissue has a vast network of blood vessels and nerve fibers, but a good vascular supply is particularly prominent in areas that contain a supply of red bone marrow. Each major vessel passes into the bone at a designated location and subsequently supplies a targeted area within the bone. Each major artery is accompanied by one or more veins, as well as a number of nerve fibers, to their targeted location. In addition to this, the periosteum has its own large supply of sensory nerves. Some of these fibers also carry pain sensations, which are initiated during extreme stress to a bone, such as a bone fracture, or growth of a bone tumor.

Answer 32

Periosteal arteries enter the shaft of a bone through a number of perforating canals known as Volkmann's canals. These vessels supply the outer part of the compact bone and periosteum.

Answer 33

The nutrient artery is located towards the center of the cylindrical shaft of a bone. It travels through the shaft, via a hole called the nutrient foramen, where it then divides and travels to the proximal and distal ends of the bone. The nutrient artery is responsible for serving the inner part of the compact bone, the spongy bone, and the bone marrow. It is usually accompanied by one or two veins.

Answer 34

The metaphyseal artery, along with the nutrient artery, provides blood supply to the bone marrow within the metaphysis.

Answer 35

The epiphyseal artery supplies blood and nutrients to the red bone marrow and bone tissue within the epiphyseal region of a bone.

Answer 36

Veins carry blood and waste products away from the bone and are usually found accompanying the main arteries. In bone, they can be found in three main locations: alongside the nutrient artery, next to the metaphyseal and epiphyseal arteries, and next to the periosteal arteries.

Answer 37

In the flat bones of the skull, the trabecular regions are drained by diploic veins, which ultimately feed into the dural venous sinuses within the skull.

Answer 38

A joint is where two or more bones meet. Also known as an articulation, these can be classified either by their structural components, the tissue that holds the bones together, or their functions, the degree of movement they provide. While these are distinct categories, there is a loose relationship between these two classification methods. Structurally, joints are classified into three main types, depending on their general morphology: fibrous, Cartilaginous, Synovial Functionally, joints are classified into three main types, depending on their function: Synarthrosis, Amphiarthrosis, Diarthrosis

Answer 39

In a fibrous joint, the two bones are connected by dense fibrous connective tissue and there is no synovial cavity present. Most fibrous joints allow very little movement. These joints can be either synarthrotic or amphiarthrotic. There are three different types of fibrous joints: Suture Gomphosis Syndesmosis

Answer 40

Suture joints are strong, synarthrotic, fibrous joints. The bones are joined together by a fibrous sutural ligament that becomes continuous with the periosteum of the bones. These joints can interlock like a puzzle or can consist of relatively straight, non-overlapping edges. Suture joints are only found in the junctions between the plate bones of the skull. Example: The sagittal suture between the two parietal bones.

Answer 41

Also called the dentoalveolar joint, the gomphosis joint is formed by a peg-like process fitting into a socket. The tooth socket is the only example of this type of joint. The tooth is held in place by a thin fleshy fibrous membrane called the periodontal ligament, which lies between the tooth and alveolar sockets of the mandible and maxilla. These joints are synarthrotic. Example: The roots of a tooth and the alveolar sockets in the maxilla or mandible.

Answer 42

Syndesmosis joints occur between two bones bound together by an interosseous ligament, consisting of long collagenous fibers. These connecting fibers can vary in length, directly affecting the joint's range of movement. These joints are amphiarthrotic. Example: The anterior tibiofibular ligament that connects the distal tibia and fibula.

Answer 43

In a cartilaginous joint, the two bones are connected by hyaline cartilage and there is no synovial cavity. These joints can be either synarthrotic or amphiarthrotic. There are two types of cartilaginous joints, synchondroses and symphyses

Answer 44

Bones in a synchondrosis joint are connected by a layer of hyaline cartilage. Nearly all synchondrosis joints can be classified as synarthrotic. With age, these joints change into a synostosis as they ossify to become a continuous bone. They are also primary cartilaginous joints. Example: The costal joint between the first rib and the manubrium of the sternum.

Answer 45

In a symphysis joint, the articulating ends of two bones are covered with a layer of hyaline cartilage which is then fused to a flat disc of fibrocartilage. These joints act as shock absorbers; fibrocartilage is resilient to stress and can be compressed. Most of these joints tend to be found in the axial skeleton, towards the midline of the body. Symphyses joints can also be classified as amphiarthrotic joints. Example: The intervertebral joints between vertebral bodies.

Answer 46

Synovial joints are characterized by the presence of a synovial cavity; a fluid-filled space found between the articular surfaces of the joints. The arrangement of these joints allows for a wide range of movement, including uniaxial, biaxial, and multiaxial movement. This freedom of movement classifies synovial joints as diarthroses joints, and most of the joints in the limbs belong in this category. All synovial joints have the following distinguishing features:

Answer 47

Articular cartilage is a thin layer of hyaline cartilage covering the articular surfaces of the bones within a joint. The function of this cartilage is to reduce friction between the bones and to act as a shock absorber as the joint moves.

Answer 48

The synovial (joint) cavity is the name given to the space that lies between two articulating bones. It contains a small amount of synovial fluid and can only be found in synovial joints.

Answer 49

The articular (joint) capsule surrounds any surface within the interior joint that is not covered by hyaline cartilage, such as the synovial cavity and synovial joint. The capsule consists of two layers: an external fibrous membrane, and an internal synovial membrane. The fibrous membrane is composed of tough, irregular connective tissue composed mainly of collagen fibers. It attaches to the periosteum of the articulating bones, and provides the joint with its tensile strength and flexibility. The inner synovial membrane is composed of loose, areolar connective tissue.

Answer 50

Synovial fluid is a viscous, clear fluid that occupies most of the free space within the joint capsule. When a joint becomes active, the fluid becomes thinner and less viscose. Synovial fluid is primarily composed of hyaluronic acid secreted by cells in the synovial membrane and interstitial fluid filtered from blood plasma. It also contains macrophages to remove cellular debris resulting from use of the joint. The main function of synovial fluid is to lubricate the joint, helping to reduce friction between the articular cartilage, and to absorb shock created by movement.

Answer 51

There are two main forms of accessory ligaments: intracapsular ligaments and extracapsular ligaments. These serve to stabilize the joint. Intracapsular ligaments are found within the articular capsule, outside of the synovial cavity. Examples include the cruciate ligaments of the knee. Extracapsular ligaments are found outside of the joint capsule. Examples include the tibial collateral ligament of the knee.

Answer 52

An accumulation of adipose tissue, called a fat pad, is present between the fibrous capsule and the synovial membrane of a bone. This cushioning pad is found in most synovial joints. An example includes the infrapatellar fat pad of the knee. Some joints also have a cartilaginous disc that lies between the two bones for additional cushioning.

Answer 53

Although not part of a synovial joint, bursae and tendon sheaths are usually found in close proximity to this type of joint. Bursae are fibrous, slightly flattened sacs, lined with synovial membrane and containing a thin film of synovial fluid. These structures are usually found between bone and other tissues, such as skin, tendons, muscles, and ligaments. Bursae function to cushion the movement between these structures as they rub together. Tendon sheaths are also structures that act to reduce joint friction. They are essentially elongated bursae that wrap around certain tendons particularly subjected to stress. Tendon sheaths tend to be found primarily at joints that undertake a high degree of movement.

Answer 54

Synovial joints can be described as being uniaxial (moves in one plane), biaxial (moves in two planes, at right angles), or multiaxial (moves in multiple planes). There are six types of synovial joints, each classified by the type of movement produced by the joint:

Answer 55

Hinge joints are uniaxial. Their movement is restricted to one plane by the shape of the opposing articular surfaces, as well as by the strong collateral ligaments along the sides of the joint. Only extension and flexion of the joint are possible here. Example: Elbow joint.

Answer 56

Gliding joints are uniaxial. Their articular surfaces are relatively flat, and they slide over each other from side to side. The angle of the bones does not significantly alter, meaning that movement in this type of joint is fairly limited. Example: Intercarpal bones.

Answer 57

Pivot joints are uniaxial. This joint consists of a bony pivot or projection that articulates with an osteoligamentous ring. Pivot joints function by rotating the bone around its own long axis. Example: Superior radioulnar joint.

Answer 58

Saddle joints are biaxial. These joints are formed between two bones that possess both concave and convex surfaces. The concave surface of one bone will then articulate with the convex surface of another. Example: Carpometacarpal joint of the thumb.

Answer 59

Condyloid (ellipsoidal) joints are biaxial . This joint is formed by the oval, convex condyle of one bone fitting into the oval, concave depression of the opposing bone. Condyloid joints permit rotation around two axes and allow angular movements such as flexion, extension, abduction, and adduction. Example: Radiocarpal joints.

Answer 60

Ball-and-socket joints are multiaxial. They are the most flexible of the joints in the body and provide almost complete rotation on all axes and planes. Ball-and-socket joints consist of a hemispherical (or spherical) head that fits into a cup-like depression in the opposing bone. Example: Glenohumeral joint (shoulder joint).

Answer 61

There are a number of terms used to describe the movements that occur within joints. These terms are important to understand as they are also used when describing muscle actions. Range of motion is the term used to describe the limits at which a particular joint can move. It is affected by a number of factors including the shape of the articular surfaces, the strength and laxity of the surrounding capsule and ligaments, and the action and strength of the surrounding muscles.

Answer 62

Decreases the angle of a joint.

Answer 63

Increases the angle of a joint.

Answer 64

Moves a part of the body away from the midline.

Answer 65

Moves a part of the body towards the midline.

Answer 66

Moves a bone vertically upwards.

Answer 67

Moves a bone vertically downwards.

Answer 68

Moves a joint horizontally forwards.

Answer 69

Moves a joint horizontally backwards.

Answer 70

Moves the mandible laterally.

Answer 71

Moves the mandible medially.

Answer 72

Moves a part of the body so that it follows a circular path. The movement is created by a combination of flexion, extension, adduction, and abduction.

Answer 73

Moves a bone around its axis.

Answer 74

Turns a bone laterally on its longitudinal axis.

Answer 75

Turns a bone medially on its longitudinal axis.

Answer 76

Rotates the forearm and hand, and the foot and ankle, upwards.

Answer 77

Rotates the forearm and hand, and the foot and ankle, downwards.

Answer 78

Moves the thumb towards the fingertips.

Answer 79

Moves the thumb away from the fingertips.

Answer 80

Flexes the ankle joint.

Answer 81

Extends the ankle joint.

Answer 82

Lifts the medial side of the foot.

Answer 83

Lifts the lateral side of the foot.

Answer 84

The temporomandibular joint is formed by the mandible and the temporal bone of the skull. Between the two bones lies an articular disc, which cushions the joint, permitting even more movement. It is the only movable joint between the bones of the skull. Bones involved Mandible: condylar process Temporal bone: mandibular fossa Joint types Condyloid Hinge Gliding Range of movement Depression and elevation Protraction and retraction Lateral and medial excursion Synovial membrane The joint is surrounded by a synovial membrane that attaches to the margins of the articular surfaces of the skull and the mandible. It also attaches to the margins of the articular disc, forming two separate joint cavities. Joint capsule The joint capsule covers the synovial membrane. Support The joint is supported by the: Lateral temporomandibular ligament Sphenomandibular ligament

Answer 85

The glenohumeral joint is formed by the spherical head of the humerus and the cup-shaped glenoid cavity of the scapula. It is the most flexible joint in the body. Bones involved Scapula: glenoid fossa Humerus: head Joint type Ball-and-socket Range of movement Circumduction Flexion and extension Lateral and medial rotation Abduction and adduction Synovial membrane The non-articular surfaces of the joint are lined by a synovial membrane, which communicates with the subscapular bursa. The tendon of long head of biceps enters the joint space through the bicipital groove, and lies in a tubular synovial sheath as it passes posteriorly and medially across the superior aspect of the humeral head. Joint capsule The loose joint capsule covers the synovial membrane. It is lax inferiorly, allowing greater mobility. There are usually two openings in the capsule, one for the passage of long head of the biceps tendon and one for communication with the subscapular bursa. Support The glenoid fossa of the scapula is slightly deepened by the cartilaginous ring of the glenoid labrum. The capsule is reinforced by three ligaments which act to stabilize the joint when it is at the limits of its range of motion. These ligaments are: Superior glenohumeral ligament Middle glenohumeral ligament Inferior glenohumeral ligament Because of the large range of motion of the joint, it must rely on the co-ordinated actions of the rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor) as well as the tendon of biceps brachii to maintain its stability. These muscles provide more stabilization to the shoulder joint than all its ligaments and capsular fibers combined together.

Answer 86

The elbow joint is a compound synovial joint composed of three articulations: the humeroulnar, humeroradial, and proximal radioulnar articulations, bound together by one joint capsule. The complexity of the opposing articular surfaces, as well as the strong collateral ligaments, restricts its motion and maintains its stability. HUMERORADIAL JOINT: Bones involved Humerus: capitulum Radius: head Joint type Hinge Movement available Flexion and extension HUMEROULNAR JOINT: Bones involved Humerus: trochlea Ulna: trochlear notch Joint type Hinge Movement available Flexion and extension PROXIMAL RADIOULNAR JOINT: Bones involved Radius: head Ulna: radial notch Joint type Pivot Movement available Rotation Synovial membrane The synovial membrane lines the joint capsule. Joint capsule The fibrous capsule completely encloses the elbow joint, but does not attach to the radius. Support The sides of the capsule are strongly reinforced by three ligaments: Medial ulnar collateral ligament Radial collateral ligament Annular ligament

Answer 87

The hip joint is formed by the spherical head of the femur and the cup-shaped depression of the hip bone. It is a stable joint with a limited range of movement. Bones involved Hip bone: acetabulum Femur: head Joint type Ball-and-socket Range of movement Adduction/abduction Flexion/extension (the most common hip movements) Circumduction Medial/lateral rotation Synovial membrane The joint is lined by a synovial membrane, which covers the capsule and the labrum and forms a sleeve around the ligament of the head of the femur. Joint capsule The joint is enclosed in a very strong fibrous capsule. Support The socket of the hip bone is deepened by a ring of cartilage called the acetabular labrum. The capsule is also reinforced by three ligaments: Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament

Answer 88

The knee is a complex joint that is actually formed by two separate joints: the femoropatellar joint, between the patella and the front of the femur, and the femorotibial joint, between the femur and the tibia. Bones involved Femur: lateral condyle Femur: medial condyle Tibia: lateral condyle Tibia: medial condyle. Patella: articular facets. Joint types Hinge Gliding Range of movement Flexion/extension Rotation Synovial membrane The joint is lined by a synovial membrane that extends superiorly from the upper border of the patella, between the femur and the quadriceps tendon, to form the suprapatella bursa. Posteriorly, it is reflected forwards to cover the cruciate ligaments, which are located outside the synovial cavity. Joint capsule The capsule and synovial membrane surround the entire joint to create a single synovial cavity. Support Within the knee joint, attached to the tibial condyles, are two fibrocartilaginous discs: the medial and lateral menisci. The menisci increase the congruence between the articulating surfaces of the tibia and femur. The knee also has several strong intracapsular and extracapsular ligaments: Intracapsular ligaments: Anterior cruciate Posterior cruciate Extracapsular ligaments: Tibial collateral Fibular collateral

Bones and joints Flashcards

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