Lecture 2 - Terminology, landmarks and skeletal system Flashcards
Describe what is meant by the anatomical position
The anatomical position describe the body position from which the directional terms always reference:
- Person stands erect
- Feet parallel, flat on the floor
- Arms at the sides of the body, palms facing forward
Describe the following body positions:
Supine
Prone
- Supine describes the body facing up
- Prone describes the body lying down
Define the following terms:
Distal
Unilateral
Medial
Proximal
Lateral
Posterior
Superior
Distal - further from the trunk
Unilateral - on one side only
Medial - towards the midline
Proximal - Nearer to the trunk
Lateral - away from the midline
Posterior - nearer the back (dorsal for NS)
Superior - towards the top
Explain the difference between the following planes:
- Coronal
- Sagittal/Medial
3.Horizontal/transverse/axial
- Separating the body front and back
- Separating the body left and right
- Separating the body top and bottom
List 4 functions of the human skeleton
- Provides the body framework
- Forms boundaries (skull, thorax)
- Permits movement (joints)
- Haematopoiesis (formation, development of blood cells in the red bone marrow)
- Mineral homeostasis (calcium, phosphate, magnesium)
- Triglyceride storage (yellow bone marrow)
- Protection (ribs)
Which bone building cells synthesise and secrete collagen and other components of bony matrix?
Osteoblasts
What are mature bone cells called and what is their function?
Osteocytes maintain the daily metabolism of bone such as nutrient and waste exchange
Which bone cell can transform into an osteocyte?
Osteoblast
Describe 3 features of compact bone
- Haversian canal: space for the blood vessels and nerves
- Lamallae: concentric rings of calcified extracellular matrix containing minerals and collagen
- Canaliculi: a mini system of interconnected canals that provides a route for nutrients and waste
- Lacunae: small spaces between the lamellae and osteocytes
What is the structural unit of compact bone called?
An osteon
What percentage of the skeleton is compact bone?
80%
Where is compact bone located?
Compact bone (or cortical bone) is found beneath the periosteum (two-layered vascular membrane) of all bones and makes up the bulk of the diaphysis of long bones.
Explain what is meant by resorption
The breakdown of bone matrix
Describe 2 features of spongy bone
- Spongy bone consists of an irregular lattice of think columns called ‘trabeculae’ that are arranged along lines of stress.
- Microscopic spaces between the trabecular make the bone lighter and contains red bone marrow, which produces blood cells, as well as blood vessels that nourish the bone.
Where is spongy bone located in the body?
In the interior of short, flat and irregularly shaped bones and the ends of long bones.
Why is spongy bone always covered by compact bone?
Because spongy bone is much softer and vulnerable to injury, it is always covered by hard and protective company bone.
What is the most abundant mineral found in bone?
Calcium phosphate (which combines with other minerals such as magnesium, sulphate and potassium).
Name 5 examples of a long bone
Femur
Tibia
Fibula
Humerus
Radius
Ulna
The epiphysis is separated from the diaphysis by the __________ plate, which is a layer of _________ cartilage that allows the diaphysis to grow in length. The epiphysis contains a region of thin outer _________ bone covered by hyaline cartilage. There is an inner spongy bone with _______ bone marrow. The diaphysis contains an outer compact bone covered by ____________. It contains a central ___________ cavity that contains ________ and ___________ bone marrow.
epiphyseal growth
hyaline
compact
red
periosteum
medullary
red
yellow
What is the periosteum?
The periosteum is a pain-sensitive, highly vascular membrane that protects bone and serves as an attachment for ligaments and tendons.
What do the following terms mean:
- Diaphysis
- Epiphysis
- The tubular shaft of long bones
- The proximal and distal ends of long bones
What is the periosteum? Describe 3 functions thereof.
The periosteum is a pain-sensitive, highly vascular membrane that protects bone and serves as an attachment for ligaments and tendons.
Describe the difference between the inner and outer layers of the periosteum.
The outer layer is tough and fibrous and is protective. The inner ‘osteopenic’ layer contains osteoblasts and osteoclasts, assisting in bone growth and repair.
Apart from long bones, name 4 types of bones and list 1 example for each bone.
Short bones: carpals, tarsals
Irregular bones: vertebrae
Flat bones: cranium, scapula, pelvis
Sesamoid bone: patella
Describe the difference between intramembranous and endochondral ossification
With intramembranous ossification, bone develops from connective tissue sheets. All flat bones develop this way (skull, clavicles etc.)
In the case of endochondral ossification, bone develops by replacing hyaline cartilage
Identify which bone grows lengthwise.
Long bones elongate from the epiphyseal growth plate until the early twenties.
List 2 factors that influence bones to grow in thickness
Physical stress
Muscle activity
Weight
Explain the role of the epiphyseal plate.
During childhood, long bones continue to lengthen because the epiphyseal plate (made of cartilage at each end of the bone) continues to produce new cartilage on its diaphyseal surface. This cartilage is then turned to bone.
Name 2 hormones that promote osteoblast activity.
Growth hormone
Calcitonin
Name 2 hormones that promote osteoclast activity
Parathyroid hormone
Cortisol
Name 2 glands in the body that regulate calcium exchange.
Thyroid gland
Parathyroid gland
Describe in detail what happens to restore balance when:
1) blood calcium is low
2) blood calcium is too high
1) Sensors pick up low levels of blood calcium and parathyroid hormone is released which stimulates osteoclast activity, releasing calcium into the blood from the bone (resorption). The kidneys are also stimulated to reabsorb and retain calcium in the blood. Furthermore the formation of calcitriol is increased, which promotes calcium uptake from food in the intestines.
2) Sensors pick up high levels of calcium in the blood, stimulates the releases of calcitonin from para-follicular cells in the thyroid gland, which promotes osteoblast activity. This leads to the absorption of calcium back into the bone, and thus increased bone formation.
Describe the role of the following vitamins and minerals in the regulation of blood calcium
a) vitamin D
b) vitamin K2
c) magnesium
a) Vitamin D3 assists the absorption of calcium from the intestinal tract into the blood
b) Vitamin K2 activates a protein called osteocalcin which controls utilisation of the calcium in the body
c) Magnesium is a co-factor needed for the conversion of Vitamin D in the body
Name 2 reasons why a patient might be deficient in Vitamin D
- Lack of sun exposure
- Reduced dietary absorption
- Reduced ability to produce active form of vitamin D (Calcitriol) in the skin, liver and kidneys
In the body, mechanical stress leads to increased __________ deposition and increased __________ production.
mineral
collagen
Does parathyroid hormone increase or decrease blood calcium?
Increase
What type of exercise promotes bone building and why is it important?
Weight bearing exercise builds bone in that it ensures bone formation occurs more quickly than bone resorption. Lack of stress on bones can cause mass loss of up to 1% per week eg/ bedridden patients and is a risk factor for osetoporosis.
Explain the difference between the axial and the appendicular skeleton?
The axial skeleton is the ‘central skeleton’ and contains 80 bones including the skull, inner ear bones, hyoid, thoracic cage and vertebral column. It servces to protect the body’s most vital organs.
The appendicular skeleton consists of the bones supporting the extremities/limbs and has 126 bones. These are the shoulder girdle, arms, hands, pelvic girdle, legs and feet. They function to enable movement as well as organ protection.
How are skull bones joined together?
With fibrous joints (sutures)
Name 2 functions of the vertebral column.
- Protection for spinal cord
- movement (side bending)
- support of skull
- forms axis of the trunk