Anatomy of bones and joints

Question 1

Briefly explain the concept of joint stability. 


Answer 1

Joint stability refers to the resistance offered by various musculoskeletal tissues that surround a skeletal joint. Several structures influence the stability of a joint:
• Shape of articulating surfaces
• Fibrous capsule & ligaments
• Muscles

Question 2

Briefly describe the blood and nerve supply to joints. 


Answer 2

• Joints have a rich blood & nerve supply
• Common around joints: anastomoses (branching of vessels)
• Hilton’s law: The nerve supplying a muscle that crosses a certain joint, also innervates this joint.

Question 3

Describe some elementary joint pathology. 


Answer 3

• Trauma
• Arthritis – pain in joints linked to inflammation, osteoarthritis (defect in cartilage making movement difficult) and rheumatoid arthritis (autoimmune disorder)
• Craniosynostosis – premature closing of cranial sutures, leading to abnormal deformed skull growth, which can affect brain development and trap nerves etc

Question 4

Describe the anatomical position and its importance

Answer 4

• Standing upright
• Head facing forward (anteriorly)
• Upper limbs by sides, palms facing anteriorly, fingers together
• Lower limbs straight, heels together, toes directed anteriorly
• In males: erected penis
• Anatomical position important as a common reference point

Question 5

Define a joint and its functions

Answer 5

• Union between two or more rigid components (bone or cartilage)
• Area of articulation
• Joints are needed for movement and growth

Question 6

What produces hyaline cartilage?

Answer 6

Chondrocytes

Question 7

Describe the structure of a synovial joint

Answer 7

Start on the inside and proceed to the outside:

1. Bones & articulating surfaces (hyaline cartilage from chondrocytes)
2. Synovial membrane
3. Intracapsular structures - discs, menisci, etc.
4. Capsule
5. Extracapsular structures - bursae
6. Stabilizing ligaments
7. Nerve and Arterial supply
8. Movements permitted & Muscles

Question 8

Describe some different types of synovial joints, giving examples for each

Answer 8

Hinge - elbow
Ball and socket - hip joint
Pivot - atlantoaxial joint
Saddle - between metacarpal and trapezium 
Condylar (ellipsoid) - knuckle
Plane -  acromioclavicular joint

Question 9

Describe a hinge joint

Answer 9

Hinge – uniaxial, only permits flexion and extension e.g. elbow joint

Question 10

Describe a ball and socket joint

Answer 10

Ball and socket – multiaxial, permits movements in several axes (flexion/extension, abduction/adduction, medial/lateral rotation, circumduction). Round head fitted into a cavity e.g. hip joint

Question 11

Describe a pivot joint

Answer 11

Pivot – uniaxial, allows rotation. A round process of bone fits into a bony ligamentous socket e.g. atlantoaxial joint between atlas (C1) and axis (C2)

Question 12

Describe a saddle joint

Answer 12

Saddle – biaxial, shaped like a saddle, concave and convex, found where bones are articulated e.g. between first metacarpal and trapezium of hand

Question 13

Describe a condylar (ellipsoid) joint

Answer 13

Condylar (ellipsoid) – biaxial, permits wider range of flexion and extension, and a narrower range of abduction, adduction, and circumduction e.g. metacarpophalangeal (knuckle) joints

Question 14

Describe a plane joint

Answer 14

Plane – permits gliding and sliding movements e.g. acromioclavicular joint

Question 15

Describe the metaphysis, the diaphysis and the epiphysis of a bone.

Answer 15

The metaphysis is the wide portion of a long bone between the epiphysis and the narrow diaphysis. Is part of the growth plate in growing bones.

Question 16

Describe a condyle

Answer 16

Condyle - articular facet, smooth end of a bone covered with cartilage that articulates in a joint with the condyle of and adjoining bone.

Question 17

Describe a epicondyle

Answer 17

Epicondyle & Supracondylar region/ridge/line - protruding area above or below the condyle for attachment of ligaments and muscles that act on the joint.

Question 18

Describe a fossa

Answer 18

Fossa (fossi pl.): a shallow depression

Question 19

Describe a process of a bone

Answer 19

Process: Any projection or bump

Question 20

Describe a foramen

Answer 20

Foramen (foramena): A rounded aperture for vessels and nerves, holes and bumps

Question 21

Describe a sulcus

Answer 21

Sulcus: A narrow groove

Question 22

Describe a tuberosity

Answer 22

Tuberosity: A rough projection

Question 23

Describe a tubercle

Answer 23

Tubercle: A small rounded projection

Question 24

Describe a spine

Answer 24

Spine: A pointed process, allows attachment of muscle

Question 25

Describe the mastoid process

Answer 25

The bony prominence behind the ear

Question 26

Where is the sternal angle (angle of Louis, sternomanubrial joint)?

Answer 26

Between T4-T5

Question 27

Where is the xiphoid process (xiphisternum)?

Answer 27

On the inferior part of sternum, T9

Question 28

Where is the anterior superior iliac spine?

Answer 28

The sharp prominence at anterior end of iliac crest, L4

Question 29

Where is the anterior superior iliac spine?

Answer 29

The sharp prominence at anterior end of iliac crest, L4

Question 30

What is a germ layer?

Answer 30

A germ layer is a primary layer of cells that form during embryogenesis. Humans have three (triploblastic)

Question 31

What are the different germ layers in humans and what do they produce?

Answer 31

o Ectoderm – generates the outer layer of the embryo, and consists of epidermis, hair, nails, lens of the eye, sebaceous glands, cornea, tooth enamel, the epithelium of the mouth and nose, peripheral nervous system, adrenal medulla, melanocytes, facial cartilage, dentin of teeth, the brain, spinal cord, posterior pituitary, motor neurons, and retina.
o Mesoderm - forms muscle (smooth and striated), bone, cartilage, connective tissue, adipose tissue, circulatory system, lymphatic system, dermis, genitourinary system, serous membranes, and notochord.
o Endoderm - forms the lining cells of all the glands which open into the digestive tube, including the stomach, the colon, the liver, the pancreas, the urinary bladder, the epithelial parts of trachea, the lungs, the pharynx, the thyroid, the parathyroid, and the intestines.

Question 32

What two tissue types dont quite follow the pattern of generation from different germ layers?

Answer 32

The skin is derived from both the ectoderm (epidermis) and the mesoderm (dermis), and smooth muscle is derived from the ectoderm and mesoderm.

Question 33

Describe the axial and appendicular skeleton

Answer 33

Axial skeleton comprises of bones situated in the long axis of the body.

Appendicular skeleton comprises of bones of the limbs that are “appended” to the body via the axial skeleton

Question 34

Describe the membranes of the bone

Answer 34

Compact bone is surrounded on the outside by a periosteum and on the inside by the endosteum.

Question 35

What type of growth do bones undergo to increase in width and increase in length?

Answer 35

• Appositional – growth occurring by apposition of new bone tissue from the outside (from the periosteum) onto existing bone to increase width and thickness
• Interstitial – growth occurring by means of cell division in the cartilage growth plate, i.e. within existing bone, to increase the length of the growing bone

Question 36

What are tendons responsible for?

Answer 36

Tendons are responsible for joint movement

Question 37

What are ligaments responsible for?

Answer 37

Ligaments are responsible for joint stability

Question 38

Describe the differences between endochondral and intramembranous ossification

Answer 38

Bones become ossified (impregnation of inorganic minerals) from their initial organic state (known as osteoid) by either:
• Intramembraneous ossification: forms the flat bones of the skull, face, jaw, and centre of clavicle, ribs
• Endochondral ossification: forms most bones in the body, mostly long bones, sternum, vertebrae, fibula etc.

Question 39

Give 3 examples of fibrous joints

Answer 39

Sutures - cranium
Syndesmosis - bones linked by interosseous ligaments or a sheet of fibrous tissue e.g. between radius and ulna
Gomphosis joint - peg like process fitted into a socket e.g. articulation between teeth and alveolar process (dento-alveolar syndesmosis)

Question 40

What is another name for the primary cartilaginous joints?

Answer 40

Synchondroses

Question 41

Describe the two types of cartilaginous joint

Answer 41

Synchondroses - joined by an epiphyseal plate made of hyaline cartilage on ends of bones, allows for bone growth, disappears in adults

Symphysis - made of fibrocartilage disc, do not ossify with age, in midline and have limited movement

Question 42

What are anastomoses?

Answer 42

An anastomosis (plural anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between blood vessels, leaf veins, or streams. Common around joints.

Question 43

What is Hiltons law?

Answer 43

Nerve supplying a muscle that crosses a joint also innervates the joint

Question 44

What regions of the bone make up the growth plate?

Answer 44

Epiphysis and Metaphysis