2. Skeletal System (COMPLETED) Flashcards
What are the two types of bone formation?
Ie: The two main ossification pathways used to produce bone.
- Intramembranous ossification.
- BONE DEVELOPS FROM CONNECTIVE TISSUE SHEETS
- Connective tissue eventually becomes bone.
- This happens predominantly in the skull and clavicle… Flat bones - Endochondral ossification.
- This is the main way that we produce bones
- Bone develops by REPLACING HYALINE CARTRIDGE
What do we mean by ossification?
Ossification means to produce the bone. If we ossify something it means to harden it.
Name the hormones that promotes osteoblast activity.
(Meaning laying down bone matrix)
This is about growing bone so …
- Growth hormone and thyroid hormone work together to stimulate bone growth while sleeping at night
- Oestrogen and testosterone assist in bone formation - if lacking lose the drive to lay down bone. Hence osteoporosis from menopause
- Calcitonin stimulates osteoblast activity and moves calcium from blood to bone.
Name two hormone that promotes osteoclast activity.
(I.e. bone loss/ resorbtion)
This is about breaking down bone – resorption
o** Parathyroid hormone** activates the osteoblasts to work harder to eat the bone, breaking down minerals in the bone to return it to the blood.
If we do not have enough calcium in the diet it will be taken from the bone and eventually the bone will become thinner and more brittle leading to opsteoporosis
o Cortisol - this is our main stress hormone and it breaks down calcium in the bone and dumps it in the blood. THIS IS WHY STEROIDS AFFECT BONE DENSITY)
Explain what is meant by the anatomical position.
It is the position used from which directions of the body can be referred.
Looks like standing facing forward, feet parallel and flat on the floor, arms at the side, palms up
Describe the following body positions
Supine
Prone
a. Supine (s UP ine)
Lying on the ground face up
b. Prone
Lying on the ground face down
Distal V Proximal
Unilateral/Bilateral/Contralateral/Ipsilateral
Midline
Medial V Lateral
Anterior V Posterior
Inferior V Superior
Subcutaneous
Distal - Further away from the trunk.
Proximal - Closer to the trunk.
Unilateral - One side
Bilateral - Both sides
Contralateral - On the opposite side
Ipsilateral - On the same side
Midline is a line down the middle of the body from head to toe.
Medial - Nearer to the midline > I <
Lateral Away from the midline < I >
Anterior - Nearer to the front
Posterior Nearer to the back
Inferior Towards the bottom
Superior - Towards the top
Subcutaneous Beneath the skin
Explain the difference between the following planes:
a. Coronal
b. Sagittal
c. Horizontal
They are all cross sections of the body
a. Coronal – separates the front and back of the body (the anterior from the posterior)
b. Sagittal – Separates left and right of the body (down the midline)
c. Horizontal – separates top from bottom of the body
List FOUR functions of the human skeleton
(i) Supports framework of the body
(ii) Attachment - **a physical point of attachment for muscle, tendons and ligaments.
(iii) Forms boundaries and provides protectio**n – eg: Cranium provides brain protection; spine provides spinal chord protection; Ribs provide lung and heart protection.
(iv) Movement
(v) Haematopoiesis – Red bone marrow for the formation and development of blood cells.
(vi) Mineral homeostasis – Mostly calcium and also phosphate, magnesium and other minerals
(vii) Storage of triglycerides (yellow bone marrow)
Name the four types of bone cell and their function
Osteogenic cells.
* Bone stem cells.
* They divide to produce osteoblasts and are the only bone cell to undergo division
-
Osteoclasts (Collapse – break down)
* Huge cells derived from fusion of as many as 50 monocytes which are phagocytic white blood cells.
* Work with osteoblasts to to remodel bone throughout life -
Osteoblasts (build)
* Bone building cells. Synthesise and secrete collagen and other components of bony matrix.
* They get** trapped** in their own collagen production and become Osteocytes - Osteocytes
* Mature bone cells.
* Maintain daily metabolism of bone such as nutrient and waste exchange
Which bone cell can transform to an osteocyte?
Osteoblast
Describe THREE features of compact bone.
- Contains few spaces
- Strong
- Osteons are the functional units of compact bone, think of it like the building bricks. Osteons are aligned in the same line as stress of the body.
Where is compact bone located?
In every bone in the body, on the outside for strength.
Beneath the periosteum.
The diaphysis of long bone is mostly made up of this.
Explain what is meant by resorption
Resorption is the breakdown and assimilation of old bone in the cycle of bone growth. The process of resorption (remodeling) involves the removal of hard bone tissue by osteoclasts followed by the laying down of new bone cells by osteoblasts.
Name the structural unit of compact bone
The Osteon.
Like Trabeculae, Osteons allow the forces to be distributed evenly, therefore good shock absorbers putting less strain on the muscles and joints.
Name and explain the 4 parts of the osteon
- Haversian Canal - Contains blood vessels and nerves
- Lamellae - Concentric rings of calcified extracellular matrix containing minerals and collagen. Give the main strength to the bone
-
Lacunae- Small spaces (between neighbouring lamellae plates) and contain osteocytes
4.** Canaliculi **- Mini system of inter connected canals that provide a route for nutrients and waste. Nourish extra cellular matrix
Describe TWO features of spongy bone.
(i) The bone looks spongy with lots of gaps.
- It is within these macroscopic (large) spaces (between the trabeculae) that we find the red bone marrow. This is very important as it is where blood cells are made.
- The gaps also make bone lighter and contain blood vessels that nourish the bone.
(ii) Functional unit is trabeculae which are an irregular lattice of thin columns of bone built along lines of stress. It is not as neatly arranged as Osteons but like Osteons, it allows the forces to be distributed evenly, therefore good shock absorbers putting less strain on the muscles and joints.
(iii) It is always covered by compact bone.
Where is spongy bone located in the body?
20% of bone is spongy bone. It is in the epiphyses of long bones, and makes up most of the short, flat, irregular shaped bones.
So this is where we find bone marrow.
Explain why spongy bone is always covered by a layer of compact bone.
It is strong as it has the trabeculae bone matrix but not as strong as compact bone so compact bone protects it.
Name the most abundant mineral in bone.
Calcium Phosphate. It combines with other mineral salts such as potassium, phosphate and magnesium.
Describe the anatomy of a long bone.
Epiphysis – Top and bottom of a long bone (proximal epiphysis is closer to the trunk and distal epiphysis is further away). It contains spongy bone.
Diaphysis – shaft of the bone and it is made up of compact bone with a periosteum on the outside made of connective tissue.
Cavity, called the medulla in the diaphysis middle for nerves, blood vessels and yellow bone marrow.
Articular cartilage at the top and bottom of bone for protection from bone on bone rubbing. When they articulate with another bone, we have two softer squishy surfaces coming together. Over time this does wear away and bone on bone tension leads to osteoarthritis.
Epiphyseal plate while the bone is still in a growth phase and Epiphyseal line once the plate is fused
Name TWO examples of a long bone.
Fibia; Tibia
Humerus
Femur
Ulna; Radius
What do the following terms mean?
a. Diaphysis
b. Epiphysis
a. Diaphysis – The tubular shaft of long bones
b. Epiphysis – The proximal and distal ends of the long bone
Explain why spongy bone is always covered by a layer of compact bone.
It is strong but not as strong as compact bone so compact bone protects it
Does all bone marrow commence as yellow bone marrow?
No, all bone marrow starts off as red marrow.
As children we have red bone marrow and it forms our blood cells. Once we have grown and have stopped growing at around age of 18-21, areas that used to have red bone marrow will then contain yellow bone marrow which stores fat for energy.
If as an adult we needed lots of red blood cells, yellow bone marrow can be converted back to red bone marrow to increase the area in the skeleton available to produce higher numbers of red blood cells.
Name the functional unit of compact bone
The Osteon.
Like Trabeculae, Osteons allow the forces to be distributed evenly, therefore good shock absorbers putting less strain on the muscles and joints.
What do the following terms mean?
a. Diaphysis
b. Epiphysis
a. Diaphysis – The tubular shaft of long bones
b. Epiphysis – The proximal and distal ends of the long bone
Describe THREE functions of the Periosteum.
Covers the external surface of bone (not when it is cartilage because then it would be a joint)
It is a highly vascular pain-sensitive membrane:
- The tough outer fibrous layer protects bone
- The inner ‘osteogenic layer’ contains osteoclasts and osteoblasts for assisting in bone growth and repair
- Serves as an attachment for ligaments and tendons
Describe the difference between the outer and inner layers of the periosteum.
Outer – fibrous, strong, protective
Inner - osteogenic layer contains osteoclasts and osteoblasts for assisting in bone growth and repair
Name the five types of bone and list an example
Long - Femur, Tibia, Fibula
Short - Carpals,Tarpals
Flat – skull, scapula, pelvis
Irregular – vertebrae
Sesamoid - Patella
List TWO factors that influence bones as they grow in thickness.
Osteoblasts in the periosteum are responsible for growing the thickness in bone. These are stimaulated by:
- Physical stress
- Muscle activity
- Weight bearing
Explain the role of the epiphyseal plate.
It is responsible for the growth of long bones. The epiphyseal plate is situated at the proximal and distal ends of long bones in between the diaphysis and the epiphysis.
Cartilage cells undergo mitosis»_space;> when they stop dividing minerals start to deposit»_space;»> osteoblasts and osteoclasts come in to form new bone.
They allow bones to grow up until the ages of approximately 18-21. After this the cartilage covering the epiphyseal plate is converted into bone and becomes the epiphyseal line.
Why do steroids affect bone density if used for a long time?
It breaks down calcium in the bone
Name TWO glands in the body that regulate calcium exchange.
Parathyroid gland releases parathyroid hormones
Thyroid gland releases Calcitonin
Describe in detail what specifically happens to rectify when blood calcium levels are too high or too low.
99% of calcium is stored in bones
Calcium exchange is regulated by the thyroid and parathyroid glands
a. Blood calcium levels too low – Hypocalcaemia.
The parathyroid hormone ….
- Increases the activity of Osteoclasts – resorption to release calcium into the blood
- Stimulates the kidneys to reabsorb and retain calcium in the body so that it is not excreted
- Increased formation of calcitriol (vit D) which pulls calcium from the intestines.
Calcitriol is the active form of Vitamin D
b. Blood calcium too high – Hypercalcaemia.
The thyroid gland …
- releases the hormone Calcitonin
- Calcitonin does the exact opposite of the parathyroid hormone. It inhibits Osteoclasts and promotes osteoblasts deposition of calcium in the bones
- Leading to increased bone formation and decereased blood calcium
Note:
Calcitriol related to osteoclasts
Calcitonin to osteoblasts
What is the name for the active form of Vitamin D
Calcitriol
Why do blood calcium levels have to be tightly controlled
To ensure proper
- blood clotting
- nerve function
- muscle function
Describe the role of the following vitamins and minerals in the regulation of calcium in the body:
a. Magnesium
b. Vitamin D
c. Vitamin K2 Potassium)
Vitamin D facilitates calcium absorption in the intestines and is directly involved with bone turnover
Magnesium needed to convert Vit D»_space;> Vit D needed to absorb calcium»_space;» Vit K2 needed for calcium to utilised in bone formation
Name TWO factors that contribute to Vitamin D deficiency.
- Lack of sun
- Lack of Vit D in the diet although we are not likely to get enough Vit D from the diet anyway
- Lack of dietary absorption of Vit D
- Lack of K2 so it is not being deposited in the bone
- Lack of magnesium and therefore the active form of Vit D
- Skin or liver or kidney problem leading to reduced ability to produce active form of Vit D
- High alcohol intake reduces VIT D conversion to aits active form
State the type of exercise that promotes bone building and explain why i
- Mechanical stress (ie: weight bearing exercise) stimulates osteoblasts leads to increased mineral deposition and increased collagen production
- This balances out resorption
- Lack of stress on bones can cause up to 1% bone loss in a week. Eg: bedridden patients, astronauts
Explain the difference between the ‘axial’ and ‘appendicular’ skeleton.
The axial skeleton is the central part of the skeleton – the trunk and the head. It comprises 80 bones and protects the bodies most vital organs
The appendicular are the bones supporting the appendages that come off the axial. It is the distal skeleton. It comprises 126 bones.
Explain why spongy bone is always covered by a layer of compact bone.
It is strong but not as strong as compact bone so compact bone protects it
Does all bone marrow commence as yellow bone marrow?
No, all bone marrow starts off as red marrow.
Describe the difference between the outer and inner layers of the periosteum.
Outer – fibrous, strong, protective
Inner - osteogenic layer contains osteoclasts and osteoblasts for assisting in bone growth and repair
Name the five types of bone and list an example
Long - Femur, Tibia, Fibula
Short - Carpals,Tarpals
Flat – skull, scapula, pelvis
Irregular – vertebrae
Sesamoid - Patella
List TWO factors that influence bones as they grow in thickness.
Osteoblasts in the periosteum are responsible for growing the thickness in bone. These are stimaulated by:
- Physical stress
- Muscle activity
- Weight bearing
Explain the role of the epiphyseal plate.
It is responsible for the growth of long bones. The epiphyseal plate is situated at the proximal and distal ends of long bones in between the diaphysis and the epiphysis.
Cartilage cells undergo mitosis»_space;> when they stop dividing minerals start to deposit»_space;»> osteoblasts and osteoclasts come in to form new bone.
They allow bones to grow up until the ages of approximately 18-21. After this the cartilage covering the epiphyseal plate is converted into bone and becomes the epiphyseal line.
Why do blood calcium levels have to be tightly controlled
To ensure proper
- blood clotting
- nerve function - conduct electrical signals
- muscle function - Can’t contract a muscle without calcium
Name FOUR components of the axial skeleton.
a. Skull
b. Vertebral column
c. Intervertebral discs
d. Thoracic
