The muscular skeletal system

What are the three types of muscular tissue?

• Skeletal muscle
• Cardiac muscle
• Smooth muscle

What is skeletal muscle?

Skeletal muscle is mostly attached to bones, it is striated and voluntary.

What is cardiac muscle?

Cardiac muscle forms the wall of the heart, it is striated and involuntary.

What is smooth muscle?

Smooth muscle is located in the internal organs, it is nonstriated and involuntary.

What is skeletal muscle tissue?

It is the muscle attached to the bones of the skeleton. 

What are the 5 key functions of muscular tissue?

• Producing body movements.
• Stabilising body positions.
• Regulating organ volume
• Moving substances within the body.
• Producing heat.

What are the 6 functions of bone and the skeletal system?

• Support- provides a framework for the body.
• Protection- protects many internal organs from injury.
• Assitance in movement.
• Mineral homeostasis- the bone tissue stores many minerals including calcium and phosphorus.
• Blood cell protection- in certain bones red bone marrow produces red blood cells. 
• Triglyceride storgae- yellow bone marrow consits of adipose cells which store triglycerides. 

What are the four different types of bones?

• Long bones
• Short bones
• Flat bones 
• Irregular bones 

What is the structure of long bones like?

They have a greater length than width and a variable number of ends, they are usually somewhat curved for strength. 

What examples are there of long bones?

• Femur
• Tibia and fibula
• Humerus 
• Ulna and radius 
• Phalanges

What is the structure of short bones like?

Somewhat cube shaped and equal in width and length.

What examples are there of short bones?

• Wrist bones
• Ankle bones

What is the structure of flat bones like?

They are thin and provide extensive surfaces for muscle attachment.

What examples are there of flat bones?

• Cranial bones
• The sternum
• The ribes
• The shoulder blades.

What is the structure of irregular bones like?

They have complex shapes and cannot be grouped into a category. 

What are examples of irregular bones?

• Vertebrae
• Facial bones

What 7 parts does a typical long bone consist of?

• The diaphysis- the bones shaft or body- the long, cylindrical, main portion of the bone.
• The epiphyses- the distal and proximal ends of the bone.
• The metaphysis- the regions of a mature bone where the diaphysis joins to the epiphyses. In a growing bone, each metaphysis contains a epiphyseal (growth) plate that allows the diaphysis of the bone to grow in length. When the growth of the bone stops the plate is replaced by bone.
•   The articular cartilage- a thin layer of hyaline cartilage covering the part of the epiphysis where the bones forms a joint with another bone.
•   The periosteum- is a tough sheath of dense irregular connective tissue and its associated blood vessels that surrounds the bone surface wherever it is not covered by articular cartilage. The periosteum contains bone forming cells that enable the bone to grow in diameter (thickness). It also protects the bone, assists in fracture repair, helps nourish bone tissue and serves an attachment point for ligaments and tendons.
• The medullary cavity- a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow in adults.
• The endosteum- a thin membrane that lines the medullary cavity. It contains a single layer of bone-forming cells.

What are the four major cells in bone tissue?

• Osteogenic cells- unspecialised stem cells derived from mesenchyme- the tissue from which almost all connective tissues are formed. They are the only none cells to undergo cell division.
• Osteoblasts- are bone building cells. They synthesis and secrete collagen fibres and other organic components need to build the extracellular matrix of bone tissue.
• Osteocytes- mature bone cells, are the main cells in bone tissue and maintain its daily metabolism, such as the exchange of nutrients and wastes with the blood.
• Osteoclasts- huge cells derived from the fusion of monocytes (type of white blood cell) and are concentrated in the endosteum. They release powerful lysosomal enzymes and acids that digest the mineral and protein components of the bone extracellular matrix. 

What is the structure of compact bone tissue like?

Compact bone tissue contains a few spaces and is arranged in repeating structural units called osteons and Haversian systems. Each osteon consists of a central (Haversian) canal with Lamellae arranged in a circle shape.  A central or Haversian canal is a channel which consists of blood vessels, nerves and lymphatic vessels. The central canals run longitudinally through the bone. Around the canals are concentric lamellae- rings of hard, calcified extracellular matrix. The osteons form a series of cylinders that run parallel to each other in long bones along the long axis of the bone. Between the lamellae are small spaces called lacunae, which contain osteocytes. Radiating in all directions from the lacunae are tiny canaliculi, which are filled with extracellular fluid. The canaliculi connect lacunae with one another and with central canals. Therefore, an intricate canal system throughout the bone provides many routes for nutrients and oxygen to reach the osteocytes and for waste to diffuse away. Compact bone tissue is the strongest type of bone tissues and is found beneath the periosteum of all bones and makes up the bulk of the diaphysis of long bones. It provides protection and support.

What is the structure of spongy bone tissue like?

Spongy bone tissue consists of units called trabeculae, irregular latticework’s of thin columns of bone. The macroscopic spaces between the trabeculae of some bones are filled with red bone marrow. Within each trabecula are concentric lamellae, osteocytes that lie in lacunae and canaliculi radiating from the lacunae. Spongy bone tissue makes up most of the bone tissue of short, flat, irregularly shaped bones. It also forms most of the epiphyses of long bones and a narrow rim around the medullary cavity. Spongy bone tissue is different to compact bone tissue, firstly it is light and secondly the trabeculae support and protect the red bone marrow.

In what four situations does bonw formation occur?

• The inital formation of bones in the embryo and foetus.
• The growth of bones during infancy, childhood and adolescence.
• The remodelling of bone.
• The repair of fractures.

What happens during intramembranous ossification?

• The development of the ossification centre- at the ossification centre cells of the mesenchyme cluster together and differentiate, first into osteogenic cells and then into osteoblasts. Osteoblasts secrete the organic extracellular matrix of the bone.
• Calcification- Next, the secretion of extracellular matrix stops and the cells, now called osteocytes, lie in the lacunae and extend their narrow cytoplasmic processes into canaliculi that radiate in all directions. Within a few days calcium and other mineral salts are deposited and the extracellular matrix hardens of calcifies.
• Formation of trabeculae- As the bone extracellular matrix forms, it develops into trabeculae that fuse with one another to form spongy bone. Blood vessels grow into the spaces between the trabeculae. Connective tissue that is associated with blood vessels in the trabeculae differentiates into red bone marrow.
• Development of periosteum- Mesenchyme condenses at the periphery and develops into the periosteum. Eventually a thin layer of compact bone replaces the surface layers of the spongy bone, but the spongy bone remains in the centre.

What happens during endochondral ossification?

• The development of the cartilage model- at the site where the bone is going to form, the cells in the mesenchyme crowd together in the shape of the future bone and then develop into chondroblasts. The chondroblasts secrete cartilage extracellular matrix producing a cartilage model consisting of hyaline cartilage.
• Growth of the cartilage model- growth occurs by the cell division of chondrocytes.
• Development of primary ossification centre- in this region of the diaphysis, bone tissue replaces most of the cartilage.
• Development of the medullary cavity- bone breakdown by osteoclasts forms the medullary cavity.
• Development of the secondary oddification centres- these occur in the epiphyses of the bone.
• Formation of the articular cartilage and epiphyseal plate- both structures consist of hyaline cartilage.

What is the bones role in calcium homeostasis?

The role of the bone in calcium homeostasis is to buffer the blood calcium level, releasing clacium to the blood when the blood calcium level fallsand depositing caclium back into bone when the blood calcium level rises.

How does exercise effect bone tissue?

• Within limits, bone tissue has the ability to alter its strength in response to mechanical stress.
• When placed under stress the bone tissue becomes stronger though increase deposition of mineral salts and the production of collagen fibres.
• Without mechanical stress, bone does not remodel normally because resorption outpaces bone formation.
• An absence of mechanical stress weakens bone strength through decrease numbers of collagen fibres and demineralisation.

What structures are in the axial skeleton?

• Cranium
• Face
• Hyoid
• Auditory ossicles
• Vertebral column
• Sternum
• Ribs

What structures are in the appendicular skeleton?

• Clavicle 
• Scapula
• Humerus
• Ulna
• Radius
• Carpaals
• Metacarpals
• Phalanges
• Hip or pelvic bone
• Femur
• Patella
• Fibula
• Tibia
• Tarsals
• Metatarsals 

How are joints classified?

• Within limits, bone tissue has the ability to alter its strength in response to mechanical stress.
• When placed under stress the bone tissue becomes stronger though increase deposition of mineral salts and the production of collagen fibres.
• Without mechanical stress, bone does not remodel normally because resorption outpaces bone formation.
• An absence of mechanical stress weakens bone strength through decrease numbers of collagen fibres and demineralisation.

What are the types of joints that are structurally classified?

• Fibrous joints- there is no synovial activity and the bones are held together by dense irregular connective tissue rich in collagen fibres.
• Cartilaginous joints- there is no synovial cavity and bones are held together by cartilage.
• Synovial joints- the bones forming the joint have a synovial cavity and are united by the dense irregular connective tissue of an articular capsule, and often by accessory ligaments.

What are the types of joints that are functionally classified?

• Synarthrosis- an immoveable joint.
• Amphiarthrosis- a slightly moveable joint.
• Diarthrosis- a freely moveable joint, permitting several different movements and shapes.

What is the structure of a fibrous joint like?

• In fibrous joints there is no joint cavity and the bones are helped together by dense irregular connective tissue.
• A fibrous joint may be slightly movable or immovable, a slightly moveable syndesmosis such as the distal joint between the tibia and fibula, an immovable gomphosis such as the root of tooth, or a slightly movable interosseous membrane found between the radius and ulna and tibia and fibula.

What is the structure of cartilaginous joints like?

• There is no joint cavity and the bones are held together by cartilage in cartilaginous joints.
• These joints can be an immovable synchondrosis united by hyaline cartilage (epiphyseal plates) or a slightly moveable symphysis united by fibrocartilage (public symphysis).

What is the structure of a synovial joint like?

• A synovial joint contains a synovial cavity. All synovial joints are diarthroses (freely moving).
• Other characteristics of a synovial joint are the presence of articular cartilage and an articular capsule, made up of a fibrous membrane and a synovial membrane.
• The synovial membrane secretes synovial fluid, which forms a thing, viscous film over the surfaces within the articular capsule.
• Many synovial joints also contain accessory ligaments and articular discs.
• Bursae are saclike structures, similar in structure to joint capsules, that reduce friction in joints such as the shoulder and knee joints.