Musculoskeletal System Lecture 27 Flashcards
What is osteo?
Bone
What is bone in terms of the organ?
Organs made up of different types of tissues
What is bone in terms of the tissue?
One of the tissues found in the bones of the skeleton
The 6 functions of the skeletal system
- Support
- Protection
- Movement
- Calcium and phosphorus reserve
- Haemopoiesis
- Fat storage
Support
- The human body requires a rigid chassis to suspend and support its soft tissues.
- Most tissues and organs are deformable, soft, and compliant, so a strong structure is needed to hold them in place.
- Without a rigid support system, the body would collapse into a blob, as most tissues lack the stiffness needed for structural integrity.
- Bones, being dense and strong, provide this necessary framework.
Protection
- Bones play a crucial role in protecting delicate and soft tissues.
Example: The Brain - The brain is extremely soft and vulnerable.
- In its natural state, brain tissue can be easily penetrated by a finger.
- To safeguard the brain, it’s suspended in cerebrospinal fluid and encased in the skull, a strong bony structure.
Other Examples:
- The rib cage protects vital organs like the lungs and heart.
- The vertebral column (spine) protects the spinal cord, which is crucial for transmitting signals throughout the body.
- Bones take on this protective role because of their density and strength, shielding vital organs from injury.
Movement
Movement is another crucial function of the skeletal system.
Muscles, by themselves, are relatively soft and can only pull on structures they are attached to.
Without the skeleton, muscles alone wouldn’t be able to generate much movement.
The skeletal system provides rigid structures for muscles to attach to, allowing them to pull and generate motion.
Joints between bones enable coordinated movement when muscles contract and pull on the skeletal system.
While some animals use hydraulic systems for movement, humans rely primarily on muscles pulling on bones to achieve movement.
Calcium and Phosphorus Reserve (Mineral Storage)
- The skeletal system also serves as a major reservoir for essential minerals, especially calcium and phosphorus.
Calcium is critical for several physiological functions, including: - Muscle contraction
- Heart function
- Nerve conduction (involving action potentials)
- Enzyme activity
Your body maintains a tightly controlled balance of calcium in body fluids, but also requires a large reserve for quick access.
- About 99% of your body’s calcium is stored in the skeleton, with the remaining 1% being tightly regulated in body fluids.
Phosphorus is another key mineral stored in bones, playing an essential role in:
- Building cell membranes
- Constructing DNA
- Forming hormones
- Producing ATP (the body’s energy source)
Blood Production (Haematopoiesis)
- The skeletal system plays a crucial role in haematopoiesis, which is the production of blood cells.
Breaking down the word: - Haem refers to the iron-containing component of haemoglobin, related to blood.
- Poiesis means “to manufacture” or “to make.”
- Haematopoietic tissue is responsible for generating blood and is found within red bone marrow.
- Red bone marrow, so-called because of its red appearance, stores the tissue responsible for manufacturing blood cells.
Fat storage
There are areas inside your skeleton where fat is stored, and the body is highly efficient at utilizing resources without waste. When there is an abundance of nutrients, the body stores them in the bone marrow, specifically in the form of fat. This fat storage occurs in yellow bone marrow, named for its yellowish color due to the presence of lipids. In certain parts of the adult skeleton, this fat is stored. Textbooks refer to this as triglyceride storage, which is essentially the same as fat storage. This is another important function of the skeletal system.
How many bones is the skeleton made up of?
206 bones
How many bones do you have when you’re born?
270 called centres of ossification
Centres of ossification
As your bones grow and develop, centres of ossification fuse during puberty, shaping your bones. However, this process doesn’t stop in adolescence. As you age, some bones continue to fuse and connect with each other in a process known as ankylosis.
Axial Skeleton
- Consists of 80 bones
- Comprises the bones that form the central axis or column of the body.
Functions:
- Support: Provides a stable structure for the body.
- Protection: Shields vital organs (e.g., heart, lungs, liver).
- Hematopoiesis: Involved in blood cell production.
Characteristics:
- More stable compared to other skeletal parts.
- Less mobility; primarily designed for support and protection of organs rather than movement.
Key Organs Supported: Liver, lungs, heart, digestive system, etc
Appendicular skeleton
- The appendicular skeleton consists of bones that form the limbs and appendages.
Mirrored Structure:
- Bones on one side of the body are mirrored on the other side (e.g., left and right limbs).
Functions:
Movement: Designed primarily for mobility and movement.
Environmental Interaction:
- Facilitates sensing the environment.
- Allows manipulation of objects (e.g., pushing hands out into space).
- Enables movement through the environment.
Where is our fat storage bone marrow located?
Localised to the appendicular skeleton
What is haematopoietic tissue and where is it located?
Hematopoietic tissue is specialized tissue responsible for the formation and development of blood cells.
It is localised to the axial skeleton
Humerus
The bone you find between the shoulder joint and elbow joint.
Non-Uniform Structure: The humerus exhibits microstructure, indicating that its composition is not uniform throughout.
Diaphysis:
- The long shaft of the humerus is referred to as the diaphysis.
- This characteristic is typical of long bones.
Epiphyses:
- The ends of the humerus articulate with neighboring bones, forming joints.
- These articulating ends are crucial for movement and stability at the shoulder and elbow joints.
Organisation of a long bone
Each long bone has two epiphyses (one at each end) where it articulates with other bones.
The area between the diaphysis (shaft of the bone) and the epiphysis is a transitional zone.
This zone has characteristics of both the diaphysis and the epiphysis.
It is called the metaphysis.
Diaphysis structure in detail and the layers surrounding it
Bone Shape: The bone is described as a hollow cone, which provides strength while being light. The diaphysis forms the outer compact bone shell.
Compact Bone: This dense bone forms the outer layer of the bone and is thicker in areas requiring more strength.
Medullary Cavity: The hollow center of the bone, where bone marrow is located. In adults, yellow bone marrow (which stores fat) is typically found in this space.
Periosteum: A fibrous outer layer surrounding most of the bone, except at joints (where articular cartilage is present). It plays a crucial role in bone health and repair. Surgeons often peel back the periosteum during reconstruction procedures to preserve its healing properties.
Sharpey’s Fibers: These perforating fibers attach the periosteum to the bone and are made of collagen. They play an essential role in keeping the periosteum tightly bound to the bone. In cases of muscle or tendon attachment to the bone, these fibers are even stronger.
Endosteum: A fibro-cellular layer lining the inside of the medullary cavity. Although thinner than the periosteum, it shares similar functions, contributing to bone health and maintenance.
Epiphysis structure in detail
Compact Bone in the Epiphysis:
The outer edge of the epiphysis contains compact bone, which is much thinner compared to the diaphysis (the shaft of the bone).
This compact bone provides a protective and supportive outer layer but is less prominent in the epiphysis.
Spongy Bone (Trabecular Bone):
As you move into the center of the epiphysis, it is filled with spongy bone. The spongy bone has a porous structure and resembles a sponge due to its lattice-like network of trabeculae (the little bony beams and rods).
The trabeculae are surrounded by endosteum, a thin vascular membrane lining the internal surfaces of bones, including the spaces within spongy bone.
Medullary Cavity and Bone Marrow:
In the epiphysis, there’s less space for the medullary cavity and bone marrow compared to the diaphysis.
The epiphysis, especially near the axial skeleton (e.g., vertebrae, ribs, and skull), often contains red bone marrow, which is responsible for blood cell production. However, this is not always the case, as marrow types may vary depending on location and age.
Blood Vessels:
Blood vessels run through the periosteum (a dense layer surrounding the outer surface of bone), into the bone tissue, and through to the medullary cavity. These blood vessels supply the bone with nutrients and allow the haemopoietic (blood-forming) tissue to release newly produced blood cells into circulation.
Articular Cartilage:
Unlike other parts of the bone, the articular surface (the surface of the epiphysis that forms joints) is covered by articular cartilage rather than periosteum.
This cartilage provides a smooth, protective surface, reducing friction between bones when they come into contact at joints.
Forces on the Femur and Pelvis
- When looking at the load transferred from the pelvis to the femur, it’s important to note that the load is off the axis of the femur’s main shaft.
- This creates a bending force on the femur, and the trabeculae are aligned to handle both compression and tension.
- Bone is not only effective at resisting compressive forces but also does an excellent job at resisting tensile forces due to the specific orientation of the trabeculae in areas experiencing tension.
Bone Marrow
- Inside the bone, you will find haematopoietic tissue (bone marrow), which is packed tightly within the trabeculae spaces.
- No space is wasted, as bone marrow fills up every available cavity in the trabeculae, which can be problematic when physicians need access to bone marrow for procedures.
- Conditions like leukaemia and lymphoma require access to bone marrow for sampling or treatment, such as cleaning and reseeding the bone marrow after treatment.
What is this cell?
Osteogenic cell
What is this cell?
Osteoclast
What is this cell?
Osteoblast
What is this cell?
Osteocyte
