Joints & Bone Growth & Types

Question 1

Name the 3 main types of joints

Answer 1

. Fibrous joints, cartilaginous joints, synovial joints

Question 2

Fibrous Joints
Structure

Answer 2

Structure
Bones connected by dense fibrous connective tissue- mainly collagen
No joint capsule/ joint cavity
Sutures - between flat bones
Syndesmoses - between l 2ong bones e.g. Interosseous membranes between radius/ulna and tibia/fibula

Question 3

Fibrous Joints - Function

Answer 3

Restricts range of movements, main function is stabilising
They are a stable joint and restrict movement at the joint

Question 4

Cartilaginous joint

Answer 4

Structure
Bones connected by fibrocartilage and hyaline cartilage

Primary: synchondroses only hyaline cartilage, found in developing bones at growth plates

Secondary: Symphyses have fibrocartilage and hyaline cartilage, found at joints along the midline (intervertebral discs, pubic symphysis)
unction
Secondary joints can be symphyses, fibrocartilage or midline joints
Allow more movement than fibrous but less than synovial

Question 5

Synovial Joint
- Structure & Function

Answer 5

Structure
Fibrous joint capsule, the joint capsule contains synovial fluid as a lubricant and shock absorber
Synovial membrane lines the capsule
Articular c ratilage on the ends of the bones

Function

Allow greater movement of bones relative to each other

Structures in the joint capsule reduce damage to bone by acting as lubricants and shock absorbers

Question 6

Synovial Joint
- Structure & Function

Answer 6

Synovial joints:

A fibrous joint capsule with a joint cavity- a potential space for synovial fluid

There is a synovial membrane lining the cavity

There is articular (hyaline) cartilage at the end of each of the bones in the joint

It allows a range of movement of the bones, relative to one another

Saddle joint, hinge joint, pivot joint, ball and socket joint, ellipsoid joint

Question 7

Architecture of Bone -
Bone is a highly v……., l…… tissue and is constantly being ….

Answer 7

vascular
living
remodelled

Question 8

Growth of long bones
remodelling occurs by ….. and ,,,, breaking down and reforming bone respectively

Answer 8

osteoclasts and osteoblasts

Question 9

Name the two types of growth which can occur in bones

Answer 9

Epiphyseal growth & Appositional growth

Question 10

Describe when epiphyseal growth occurs?

Answer 10

Epiphyseal growth occurs as bones are developing and growing and starts at the epiphyseal plates on long bones which are layers of cartilage from which bones develop

Question 11

Describe the process of epiphyseal growth

Answer 11

Chondrocytes proliferate and move into mature zone (stimulated by IGF1)

They secrete ECM which separates cells

Converted to bone at the secondary ossification centres (osteoid is deposited on calcified cartilage)

Question 12

What does appositional growth lead to? Another name for appositional growth?

Answer 12

Appositional growth (acceretion) is how the diameter of long bones is increased to allow greater weight-bearing capabilities

New bone is deposited beneath the periosteum (layer adhering to the outer surface of bones)

Osteoblasts secrete bone morphogenic protein, induces new cartilage and bone formation by inducing mesenchymal cells to osteoblasts

Question 13

Name the 2 main types of bone?

Answer 13

Compact & trabecular/cancellous/ spongy bone

Question 14

. Purpose of Trabecular Bone

Answer 14

. Trabecular bone is for support & structure - gives internal supporting plates and struts while reducing mass of the bone- in the femur trabeculae are aligned with stress to transfer weight down the leg to the foot (resists tensile and compressive forces)
. Very porous so lightweight

Question 15

Purpose of Compact Bone

Answer 15

• Forms the outer coating of all bones & gives strong shafts in long bones for additional strength

Question 16

To adapt for strength & lightness, bone is made from 2 main tissue types …. and …

Answer 16

compact
trabecular/ cancellous/ spongy

Question 17

Compact bone has ….. structure in the mature bone

Answer 17

lamellar

Question 18

Elaborate on the lamellar structure that compact bone has in the mature bone

Answer 18

Compact bone has a lamellar structure in the mature bone:
Bone is arranged into structures called osteons/Haversian systems which are concentric lamellae with a central canal called a Haversian canal
Osteons in compact bone
osteon (Haversian system)
interstitial lamellae
vessels in central
(Haversian) canal
osteocytes in lacuna
vessel in perforating
(Volkman’s) canal
concentric lamellae
canaliculi
central canal
osteocytes in lacunae
circumferential
lamellae
periosteum
Osteocytes are linked
to one another and to
surface osteoblasts
(canaliculi) and gap
junctions
(communication +
nutrients)
The Haversian canal contains blood vessels (and other vessels)
Volkmann’s canals are perforating canals which also carry vessels
Osteons can move in relation to each other which helps prevent fracturing
Osteocytes are linked via canaliculi (fine processes) and gap junctions for communication and nutrient transfers

Question 19

Spongy bone

Answer 19

Marrow cavities in bone are fat storage and haematopoiesis (production of blood cells)

Question 20

REVIEW BONES

Answer 20

FILL IN THE BLANS OVER THE NEXT FEW FLASHCARDS

Question 21

Structure of Bone Tissue
- There are …. types of bone tissue: …. & …
- The names imply that the 2 types differ in d…., or how tightly packed tissue is together

Answer 21

2, compact, spongy
density

Question 22

There are …. types of cells that contribute to bone homeostasis
Name them & in half-a sentence state their function

Answer 22

3
Osteoblasts = bone forming cells
Osteoclasts = resorb or break down bone
Osteocytes = mature bone cells
An equilibrium between osteoblasts & osteocytes = maintains bone tissue

Question 23

Compact bone
- Consists of closely packed osteons or ……
- Osteon consists of a central canal also called the …../… canal, which is surrounded by …. rings (…) of matrix
- Between the rings of matrix, the bone cells …. are located in spaces called …

Answer 23

Haversian systems
Osteonic canal/ Haversian canal
concentric rings (lamellae)
osteocytes, lacunae

Question 24

Compact bone continued
Small channels called …. radiate from the …. to … for ….
- In compact bone, the Haversian systems = are tightly packed together to form what appears to be a solid mass. The osteonic canal = contains blood vessels that are …. to the long axis of the bone
These blood vessels interconnect by way of …..

Answer 24

canaliculi, lacunae to Haversian/osteonic canal
provide passageways through the hard matrix
parallel
perforating/ Volkmann’s canal

Question 25

Spong (Cancellous) Bone - is ... and ... than compact bone - Spongy bone consists of .... (plates & bars of bone) which are adjacent to small, irregular cavities that contain - The canaliculi connect to the adjacent cavities instead of a central haversian canal to receive their blood supply

Answer 25

lighter & less dense trabeculae red bone marrow

Question 26

Spongy bone continued - It may appear that the trabecular are arranged in a haphazard manner, but they are organised to provide ...... similar to braces that are used to support a building - Trabeculae of spongy bone = follow lines of .... and can .... if the ... of stress changes

Answer 26

maximum strength stress realign direction

Question 27

Bone Development & Growth - Revision Term ..../.... is used to indicate the process of bone formation

Answer 27

Ossification/ osteogenesis

Question 28

how many types of ossification are there? Name them?

Answer 28

2 - intramembranous & endochondral

Question 29

Describe intramembranous ossification

Answer 29

- Invlves the replacement of sheet-like connective tissue membranes with bony tissues - bones formed in this manner = called intramembranous bones; incude certain flat bones of the skull & some of the irregular bones - The future bones are first formed as connective tissue membranes, osteoblasts migrate to the membranes and deposit bony matrix around themselves - when the osteoblasts are surrounded by matrix they are called osteocytes

Question 30

Describe endochondral ossification

Answer 30

- Endochondral Ossification = involves the replacement of hyaline cartilage with bony tissue, most of the bones in the skeleton are formed in this manner & these bones are called endochondral bones. - in this process, the future bones are first formed as hyaline cartilage models ... tbc

Question 31

more on endochondral ossification

Answer 31

During the third month after conception, the perichondrium that surrounds the hyaline cartilage "models" becomes infiltrated with blood vessels and osteoblasts and changes into a periosteum. The osteoblasts form a collar of compact bone around the diaphysis. At the same time, the cartilage in the center of the diaphysis begins to disintegrate. Osteoblasts penetrate the disintegrating cartilage and replace it with spongy bone. This forms a primary ossification center. Ossification continues from this center toward the ends of the bones. After spongy bone is formed in the diaphysis, osteoclasts break down the newly formed bone to open up the medullary cavity. The cartilage in the epiphyses continues to grow so the developing bone increases in length. Later, usually after birth, secondary ossification centers form in the epiphyses. Ossification in the epiphyses is similar to that in the diaphysis except that the spongy bone is retained instead of being broken down to form a medullary cavity. When secondary ossification is complete, the hyaline cartilage is totally replaced by bone except in two areas. A region of hyaline cartilage remains over the surface of the epiphysis as the articular cartilage and another area of cartilage remains between the epiphysis and diaphysis. This is the epiphyseal plate or growth region.

Question 32

Bone Growth Reviewed

Answer 32

Bone Growth Bones grow in length at the epiphyseal plate by a process that is similar to endochondral ossification. The cartilage in the region of the epiphyseal plate next to the epiphysis continues to grow by mitosis. The chondrocytes, in the region next to the diaphysis, age and degenerate. Osteoblasts move in and ossify the matrix to form bone. This process continues throughout childhood and the adolescent years until the cartilage growth slows and finally stops. When cartilage growth ceases, usually in the early twenties, the epiphyseal plate completely ossifies so that only a thin epiphyseal line remains and the bones can no longer grow in length. Bone growth is under the influence of growth hormone from the anterior pituitary gland and sex hormones from the ovaries and testes. Even though bones stop growing in length in early adulthood, they can continue to increase in thickness or diameter throughout life in response to stress from increased muscle activity or to weight. The increase in diameter is called appositional growth. Osteoblasts in the periosteum form compact bone around the external bone surface. At the same time, osteoclasts in the endosteum break down bone on the internal bone surface, around the medullary cavity. These two processes together increase the diameter of the bone and, at the same time, keep the bone from becoming excessively heavy and bulky.