Support and Movement System Notes

Support and Movement System

• Druk Gyalpo Quote: "You cannot give what you do not have."

Objectives

• Develop a model relating protein arrangement in muscle fibers to contraction.
• Construct scientific explanations of bone and cartilage formation.
• Develop a model explaining muscle roles in bone movement.
• Design prosthetic solutions for skeletal limb abnormalities.

Support & Movement System

• Living things need support systems for support, movement, and survival.
• Movement Definition: Changing position by the entire body or parts.
• Kinesiology: Study of movement (GK kinein- to move).

Types of Movement

• Molecular Level: Brownian movement (zig-zag motion).
• Cellular Level: Cyclosis, sperm swimming, ciliary and flagellar movement.
• Organ Level: Heartbeat, muscle contraction.
• Organism Level: Flying, running, etc.

Types of Movement

1. Nonmuscular Movement

• A. Cytoplasmic Streaming (Cyclosis):
  • Ensures material distribution.
  • Formation of pseudopodia.
• B. Amoeboid (Pseudopodial) Movement:
  • Captures food (Amoeba).
  • Captures foreign bodies (macrophages).
• C. Ciliary Movement:
  • Propels dust particles, sperm, and ova in desired direction.
• D. Flagellar Movement:
  • Transports food, oxygen, and circulates fluid (Euglena, Hydra).

2. Muscular Movement

• Produced by muscle contraction and relaxation.
• Responsible for movement of individual organism or their body parts

Advantages of Movements to Animals

• Movements of external body parts
• Movements of internal body parts
• Movements within the cells

Locomotion

• Movement of an organism as a whole, resulting in change of place.
• Motile: Organisms with the ability to move.
• Locomotion distinguishes animals from plants.

Advantages of Locomotion

• Escape from enemies and predators.
• Search for food and water.
• Escape from unfavorable environment.
• Find mate.
• Find shelter.
• Migrate.

Support and Movement

• Human and animal support systems consist of the skeleton/skeletal system and muscular system.

Skeletal Systems

• Arthropods (crabs, grasshoppers, bees, ants) possess exoskeletons.
• Invertebrates (earthworms, sea anemones) have hydrostatic skeletons.
• Chitin Exoskeleton
• Calcium Carbonate Exoskeleton (shell)
• Hydrostatic skeleton: The fluid-filled cavity that aids movement in animals like earthworms

Functions of Exoskeleton

• Support body weight
• Maintain body shape
• Protect soft tissues from damage
• Provide surface for muscle attachment
• Allow movement

Functions of Endoskeleton

• Support body weight
• Maintain body shape
• Protects soft organs inside the body
• Provide a place for muscle in the body to attach themselves
• Enable limbs to move

Endoskeleton

• All vertebrates have an endoskeleton.
• Bones form a supporting framework for muscle attachment.
  Musculoskeletal System
  *Includes skeletal tissue (connective tissue) to protect body organs (bones, cartilage, blood) and muscular tissue (soft tissues of muscles to help with body movements).
  *All vertebrates have an endoskeleton and muscles for movement

Endoskeleton of Mammals

• Bones: Hard, made of Calcium, phosphate and Calcium carbonate
• Cartilages: Semi-rigid, made of Aggrecan, water and fiber.

Bones

• Hard tissue made of minerals (e.g., calcium phosphate, calcium carbonate).
• Components of a joint include bone, articular cartilage, articular capsule, synovial membrane, and joint cavity containing synovial fluid.

Two Skeletal Tissues

• Bone contains:
  • Cement layer.
  • Lacuna (space containing osteocyte).
  • Lamellae (bone layers).
  • Haversian canal / central canal (a longitudinal canal containing 1 or 2 blood vessels, nerves, ± a lymph vessel and fluid).
  • Canaliculi (tiny canals containing cytoplasmic processes of osteocyte).
• Cartilage contains chondrocytes.
• Bones contain more mineral salts.
• Collagen is present in superficial tangential, middle/transitional, and deep/radial zones of cartilage.

Cartilage

• Semi-rigid, flexible connective tissue.
• Provides support or bears weight.
• Acts as a template for bone formation.
• Provides rigidity and elasticity.
• Non-mineralized, while bones are mineralized.
• Made of aggrecan, water, and fibers (collagen and elastin).
• Phylogenetically older than bone tissue.
• Temporary and permanent cartilage exist.

What is Cartilage For?

• Forms the supporting framework of some organs, such as the walls of airways (nose, trachea, larynx and bronchi), where it prevents airway collapse.
• Forms the articulating surfaces of bones.
• Forms the template for the growth and development of long bones, and most of the rest of the fetal skeleton.

Skeletal Tissues

• Bones and cartilages are formed of cells, matrix, and fibers.
• The nature of bones and cartilages is determined by the types of cells, matrix, and fibres that they are made of.

Three Elements/Components of Cartilage

• 1. Cells
  • Perichondrium: Outermost layer; vascular, supplies nutrients, essential for growth and maintenance.
  • Chondrogenic cells: Found below perichondrium, undergo mitosis, differentiate into chondroblasts.
  • Chondroblast: Young cartilage cells in lacunae, may undergo mitosis, secrete extracellular matrix and chondrocytes.
  • Chondrocytes: Mature cartilage cells in lacunae, produce and maintain extracellular matrix.
• 2. Fibres
  • Collagen and elastin fibres.
• 3. Ground Substance (Extracellular Matrix)
  • Made up about 10% aggrecan (proteoglycan & glycoproteins), 75% water, and a mix of collagen fibres and other constituents.

Components of Cartilage

• Mesenchyme cell (chondroblast).
• Extracellular matrix (proteoglycans, collagen, hyaluronic acid).
• Perichondrium.
• Chondrocytes.
• Lacuna.
• Diffusion of nutrients through the extracellular matrix to chondrocytes and diffusion of chondrocyte excretory products through the extracellular matrix to circulatory system are necessary.
• Capillaries are involved in the diffusion of nutrients and excretory products in cartilage.

Cartilage (Aggrecan)

• Aggrecan only found in cartilage
• Aggrecan also known as cartilage-specific proteoglycan core protein or chondroitin sulfate proteoglycan. E.g. Chondroitin sulphate & Keratan sulphate.
• The aggrecan contain glycoprotein. E.g. chondronectin and condrocalcin (calcium- binding proteins)
• Function: provide hydrated gel structure

Two Processes of Cartilage Growth

1. Interstitial Growth

• Produced by cell division and activity of mature chondrocytes
• Synthesis of the extracellular matrix
• Expansion of the cartilage matrix from within.
• Leads to increase in length

2. Appositional Growth

• Produced by the activity and differentiation of the chondroblasts or perichondral cells
• Synthesis of the extracellular matrix
• Expansion of the girth of the cartilage.
• Leads to increase in width.

Cartilage Growth

• Appositional: Increasing in WIDTH; chondroblasts deposit matrix on the surface of pre-existing cartilage.
• Interstitial: Increasing in LENGTH; chondrocytes divide and secrete matrix from within lacunae.

Cartilage Growth Direction and Nutrition

• Growth is unidirectional, from the periphery.
• Matrix is avascular.
• Perichondrium has blood vessels.
• Cells receive nutrients and oxygen by diffusion from blood vessels in the perichondrium.
• Diffusion is possible because the cartilaginous matrix is not calcified.

Types of Cartilage

• Hyaline cartilage
• Fibrocartilage
• Elastic cartilage
• Clearer looking ground substance.
• Densely layered collagen fibers.
• More flattened and organized cell rows.
• Visible elastic fibers in matrix.

Types of Cartilage (Hyaline)

• Blue-white and translucent, homogenous, and fiberless.
• Low-friction and wear-resistant tissue.
• Aids in sliding within the bones.
• Designed to bear and distribute weight.
• Present within joints- between ribs and sternum, in the nasal septum, larynx and tracheal rings.
• It has a perichondrium, and it is the weakest of the three types of cartilage.

Types of Cartilage (Fibrocartilage)

• Tough, white, and inflexible.
• Provides protection, strength, and resistance to tearing and compression.
• Strongest due to dense collagen fibers.
• Does not have a perichondrium, as it is usually a transitional layer between hyaline cartilage and tendon or ligament.
• Found in the spine (backbone).

Types of Cartilage (Elastic)

• Chondrocytes found in a threadlike network of elastic fibres within the matrix.
• Provides strength and elasticity.
• Maintains the shape of certain structures.
• Found in the external ear and epiglottis.
• Has a perichondrium.
• Collagen and elastic fibres make it flexible.

Calcified Cartilage

• Calcium salts deposited in the matrix.
• Very hard and inelastic.
• Found in the suprascapula of pectoral girdle of frog and vertebrae of shark

Features of Cartilage

• Receives nutrition by diffusion through matrix from nearest capillaries.
• No lymphatics.
• Has thin canals to provide nutrition to deepest core.
• No nerve supply, thus, it is insensitive.

Questions to Explore

• Some lacunae contain more than one chondrocyte—why is this?
• Frequently, the chondrocytes do not fully occupy their lacunae—why is this?
• How are chondrocytes nourished?
• Why is grafting of homogenous transplantation of cartilage possible without rejection?
• Damaged cartilage shows limited repair (regeneration). Why?

Bone

• Hardest connective tissue.
• Provides support and protects soft parts of body.
• Helps in locomotion.
• Maintains optimal blood calcium level (acts as homeostatic organ).

Two Categories

• 1. Axial Bone
  • Found in head, neck, back, and chest; e.g., skull, spine, and rib cage.
  • Provides central support and protection for vital organs.
• 2. Appendicular Bone
  • Found in the appendages or limbs; e.g., arms and legs, pelvis, and shoulders.
  • Facilitates movement and interaction with the environment.

Classification of Bone by Shape

• 1. Long bone: e.g., limb bones – Structural support of skeleton
• 2. Short bone: e.g., ankles and wrists - provide support and stability with movements.
• 3. Flat bone: e.g., sternum (breast bone) – provide surface area for protection and muscles to attached.
• 4. Irregular bone: e.g., vertebrate

What do Bones Do?

• Support
• Protects
• Act as levers
• Provide mineral storage: e.g., calcium and phosphate
• Fat storage
• Hormone production (osteocalcin induce testosterone)
• Blood formation (bone marrow)
• Hearing
• Speaking
• Movement

Bone as an Organ

• Bone is regarded as an Organ, because it has:
  • Nervous tissue
  • Connective tissue
  • Cartilage
  • Blood vessels

Components of Bone

• 1. Inorganic components/salt:
  • hydroxyapatite (salt of calcium and phosphate)
  • $CaCO_3, Mg^{2+}, Na^+, S$ and $F$
• I. Organic components:
  • Osteoid-made up of jelly ground substance (matrix) made up of protein and polysaccharide and collagen fibres
  • Cells (osteoblasts, osteocytes, etc.)

Three Elements/Components of Bone

• Bone is a strong, flexible, and semi-rigid supporting tissue.
• Like cartilage, bone is made of cells, fibers, and matrix.
  • Cells: Oestoprogenitor cells, osteoblast, osteocytes, osteoclast.
  • Osteoid (Extracellular/bone matrix): Fibres (collagen fibres) and Ground substance [proteoglycans, glycoproteins(osteonectin and osteocalcin)]
  • Inorganic: Hydroxyapatite and other minerals.
  • Water (only 25% of bone is water).

Long Limb Bones

• Differentiated into Epiphysis and Diaphysis/shaft
  *What about short bones? Do they have epiphysis and diaphysis.

Anatomy of Long Bone

• Diaphysis (Shaft)
  • Made up of compact bone surrounding medullary/marrow cavity.
  • Contains yellow bone marrow.
• Epiphysis (End)
  • Made up of spongy bone within compact bone & cartilage on the joint surface.
  • Contains red bone marrow.

Parts of Bone

• Periosteum
• Compact bone
• Endosteum
• Spongy bone
• Bone marrow cavity
• Yellow bone marrow
• Periosteum-Perforating fibers
• Nutrient-arteries
• Endosteum

Two Main Types of Bones

• 1. Compact bone / periosteal bone
  • Cortical bone / hard bone / dense bone
  • Forms part of diaphysis/shaft of long bones
  • Made of Haversian systems/osteons
  • Has a single marrow cavity filled with yellow bone marrow
  • Forms 80% of the human adult bone
• 1. cancellous/trabecular bone which makes 20% of all bone
  • Majorly at the ends of long bones (in the epiphysis)
  • Present crisscrossing branches or networks (thread like bone) called trabeculae.
  • Present red bone marrow between trabeculae.
  • Trabecular has endosteum surrounding parallel lamellae (rod) with osteocytes.
  • Trabecular bone is an adaptation to compressive forces.
  • No osteon/ haversion system and less dense.

Bone Matter (Four Parts)

• 1. Periosteum (outer layer)
  • Outer covering of the bone, muscles attach to it.
  • Made up of dense irregular fibrous tissue.
  • The bundles of collagen fibres in periosteum is called sharpey-schafer fibres.
  • Present nerve fibres, blood and lymph vessels.
  • Below periosteum contain osteogenic layer with primitive stem cells to form new bone cells called osteoblasts.
  • The osteoblasts divide to form new osteocytes and secrete bone matter so that bone grows in thickness.
  • Periosteum is absent in the articulating surface of the bone.
• 2. Endosteum (inner layers of bone)
  • Contains the bone marrow cavity of the hollow bones.
  • Formed by highly vascular areolar tissue having collagen fibres, blood vessels, and osteoblasts.
  • 3. Matrix
  • Dense and hard substance made of protein ossein.
  • Matrix has depositions of calcium and magnesium salts.
  • In addition, sulphates and fluorides are also present.
  • Collagen fibres provide the bone its strength and resiliency.
  • Minerals give bone its hardness.
• 4. Bone Marrow
  • The shaft of the long bones are hollow.
  • The cavity is called bone marrow/medullary cavity.
  • It is filled with soft, fatty tissue called bone marrow.

Internal Structure of Bone

• compact bone
• medullary cavity
• spongy bone
• periosteum
• concentric lamellae
• circumferential lamellae
• periosteal artery
• periosteal vein
• outer fibrous layer
• inner osteogenic layer
• interstitial lamellae
• perforating canal
• central canal
• blood vessels
• lymphatic vessel
• nerve
• trabeculae
• osteon

Internal Structure of Compact Bone

• Present larger number of tree-like structures called Osteons or Haversian Systems.
• Osteon is the functional unit of bones.
• In the centre of osteon present Central Haversian/osteon canal with nerve and blood vessels (arteries and veins)-to supply oxygen and nutrients to the bone.
• Around the central Haversian canal, the osteocytes in lacunae arrange in concentric rings of bone matrix called concentric lamellae (little plate).
• Lacuna small space in bone tissue and cartilage housing osteocytes and chondrocytes.
  *In the periosteum and endosteum present lamellae called circumferential lamellae (outer and inner) that runs parallel.
  *Between the osteons/Haversian systems—present another lamellae called interstitial lamellae.
  *From Lacunae, the small canals called canaliculi arises into many directions and connected (interconnected) to other lacunae to provide passage for communication and nutrient delivery to osteocytes.
  *There are also another canal called horizontal/transverse/perforating/Volkmann’s canal that connects one central Haversian canal to another Central Haversian Canal. Present nerve fibres and blood vessels from the periosteum.

Structure of Compact Bone

*Lacuna
*Concentric lamellae
*Interstitial lamellae
*Haversian cartal
*Canaliculus
*Cement line

Haversian System

*Calcified matrix is deposited in lamellae
*Osteocytes and their lacunae arranged in between these lamellae
*Three distinct types of layering in the structure of bone (Three different patterns of lamellae):
*1. Haversian (Osteon) or concentric lamellae
*2. Interstitial Lamella
*3. Circumferential Lamellae—

• 1. Outer (in Periosteum)
• Inner (in Endosteum)

Structural Unit

Osteon: Haversian canal, osteocyte, canaliculi, lamella
*Volkmann canals
*STRUCTURAL UNIT OF COMPACT BONE IS THE OSTEON (HAVERSIAN SYSTEM)
*Osteocyte in Lacuna
*Canaliculi
*Osteocytes in Lacunae
*Concentric Lamellae
*Blood Vessels & Nerves in Central Canal
Periosteum → Outer Circumferential Lamellae → Osteons (Haversian Systems) → Interstitial Lamellae → Inner Circumferential Lamellae → Endosteum

Structure of Spongy Bone

Components: Spongy bone
Compact bone
Trabeculae
Canaliculi
Endosteum Lamellae
openings on the surface
Lacuna
Osteocyte
Osteoclast
Osteoblasts aligned along trabeculae of new bone
The periosteum is absent in the articulating surface of the bone in Spongy bone

Structure of Spongy Bone

*No osteons or Haversian system
*Present crisscrossing branches called trabeculae.
*Trabeculae consist of endosteum surrounding parallel lamellae with osteocytes in lacuna.
*Canaliculi provides nutrients and oxygen.

Epiphyseal Plates

• The epiphysis and the diaphysis fuse at the epiphyseal plates often called the growth plates.
• They are named because that is the region that contains cartilage where new bone is deposited during growth. This allows for the bone to increase in length.
• In humans, these cartilaginous plates become completely bony and fused (remain as epiphyseal line) when growth ceases usually between the ages of 18 and 20.

Epiphyseal Plates (Closure)

• When puberty stops, the closure of epiphyseal plates takes place.
• When the bone growth is complete, the epiphyseal cartilage is replaced with bone.
• The fractures of the epiphyseal plates in children can lead to slow bone growth or limb shortening.

Epiphyseal Plates (Structure)

• Epiphyseal Plate- a disc of cartilage that grows during childhood
• compact bone
• periosteum
• spongy bone
• articular cartilage
• marrow
• blood vessel
• epiphyseal line
• medullary cavity
• Human bone structure
• Bird bone structure

Human vs. Bird Bone Structure

• Bone usually develops first as spongy bone, but some bones, through further deposition of bone matrix, become compact.
• Based upon the mode of locomotion and metabolic demands, the bones in all vertebrates will contain compact bone, spongy bone, and marrow in varying proportions.
• For example, birds have thin layers of compact bone and little, if any, marrow.
• This evolutionary innovation helps reduce weight, making flight more efficient by making it less energetically demanding.
  *Red bone marrow
  *Present in the spongy part of long bone (i.e., epiphysis).
  *Formed by loose reticular tissue.
  *Red in color due to iron (heme).
  *Comprises of haemopoietic tissues that give rise to RBCs and WBCs.
  *Yellow bone marrow
  *Present in the shaft of the long bone (Diaphysis).
  *Comprises of adipose tissue to store fat.
  *Yellow color due to carotenoids in the fat droplets.
  *Also produce blood cells during the excessive blood loss.

Two Types of Bone Marrow

• Red bone marrow
  • Contains blood stem cells that can become RBCs, WBCs, platelets.
• Yellow bone marrow
  • Store fats, aids in production of bone and cartilage.
  • produce red blood cells during life threating situations.

Types of Cells Found in Bone

• Cells that are involved in growing bone:
  • Four types of cells: Bone lining cells, Osteogenic/osteoprogenitor cells, Osteoblasts, Osteocytes, and Osteoclasts

Bone Cells (Osteoprogenitor)

• Osteoprogenitor/osteogenic cells are responsible for bone formation.
• They are stem cells found in the periosteum and endosteum that play a role in bone repair and growth.
• They will differentiate into more specialized bone cells called osteoblasts and osteocytes and reside in the bone marrow.
• These cells are precursors to the more specialized bones cells.

Bone Cells (Osteoblasts)

• Responsible for mineralization of bone and secretes matrix.
• When osteoblasts are trapped in the matrix which they have secreted, then they become osteocytes.
• Present inside periosteum and outside endosteum.
• Divide and add new lamellae to the bone matrix and bone grows in thickness.
• After deposited of inorganic salts in the matrix, the osteoblasts are transformed into osteocytes.

Bone Cells (Osteocytes)

• Osteocytes sit in the calcified matrix, in small fluid filled cavity called lacunae (lacuna - singular).
• Neighboring lacunae are connected by canaliculi (little/small canals).
• These are channels for the transport for nutrients and waste.
• The osteocyte processes contact other osteocytes, forming gap junctions, so that they can monitor and communicate with each other.
• Osteocytes are connected through filopodia and finally with the Harversian canal for obtaining food and oxygen from the blood vessels.
• Inactive bone cells

Bone Cells (Osteoclasts)

• It also called bone phagocytes.
• Responsible for demineralization of bone or break down or dissolve bone matrix using enzyme (resorption).
• Large and multinucleated cells present on the surface of spongy bones.
• When calcium level in blood falls, osteoclast are activated by parathormone.
• The activated osteoclasts digest small portion of spongy bones, release calcium into the bloodstream and restore proper blood calcium level.
• Important role in remodeling of bone (spongy bone).

Bone Remodeling

• Bone remodeling is a lifelong process where mature bone tissue is removed from the skeleton and new bone tissue is formed.
• These processes also control the reshaping or replacement of bone following injuries like fractures but also micro-damage, which occurs during normal activity.
• Bone is a dynamic tissue, involving both destruction by bone-resorbing cells (osteoclasts) and deposition by bone-building cells (osteoblasts).
• Both processes occur simultaneously so that new osteons form as old ones are resorbed.
• The marrow cavity inside grows larger by bone resorption of the inner surface of the surrounding bone while new bone is laid down on the outer bone surface by bone deposition.

Bone Remodeling Cycle

• Pre-Osteoclasts
• Active Osteoclasts
• Pre-Osteoblasts
• Mononuclear Cells
• Osteoblasts
• Osteocytes
• Resting Bone Surface
• Resorption
• Reversal
• Bone Formation
• Mineralization

Process of Bone Remodelling

• Osteoblast sense the bone cracks and mediates bone remodeling process.
• Activate osteoclast for resorption in the crack.
• Osteoblast will form new bone cells in the cracks.
• Osteocytes

Bone Remodeling and Exercise

• Bone remodeling is a response to stress or disease
• Just as muscles, skin, and other body tissues may change depending on the stresses of the environment, bone also is a dynamic tissue that can change with demands made on it.
• The effect of remodeling can be seen by examining bone thickness in rodents forced to exercise.
• The continual stresses placed on the limb bones cause additional bone to be deposited, leading to thicker and stronger bone.
• The same phenomenon is seen in human weight lifters, who develop stronger and thicker arm bones, and equestrians (Horse rider), whose femurs become much thicker on the inner side because of the forces they exert to remain mounted.
• This phenomenon also has important medical implications. Osteoporosis, which is characterized by a loss of bone mineral density, increasing the risk of bone
  fractures.
• It affects primarily postmenopausal women, but also those suffering from malnutrition and a number of diseases.

Osteoporosis

• Osteoporosis
  • Michael Klein/Photolibrary/Getty Images; (b) Dr. P. Marazzi/Science Source
• The healthy vertebral column shows the vertebrae stacked evenly on top of each other

How to Prevent Loss of Bone Mineral Density (Osteopenia)

• Take Calcium
• Like muscle, bone is subject to "use and disuse." When we exercise our muscles, our bones respond by producing new bone tissue to give added strength.
• For example when bones are not subject to stress, as in space flight, the body resorb the mineral, and the bones become weak
• Astronauts who spend many months in space must exercise to a greater degree than on earth to prevent such resorption and bone weakness.
• Dietary supplementation with calcium and vitamin D3 has been advocated to prevent such losses, and together with exercise they can slow demineralization after menopause.
• Bone growth responds to several hormones, in particular parathyroid hormone from the parathyroid gland, which stimulates bone resorption, and calcitonin from the thyroid gland which inhibits bone resorption.
  vitamin C
  Eat Foods Rich in Vitamin C
  D
  Reduce Your Sodium Intake
  Stay Active
  Eat Magnesium Rich Foods
  QUT
  Quit Smoking
  Boost Vitamin D Intake
  Consume Less Caffeine
  Eat Vitamin K Rich Foods

Microscopic Structure of Bones

• Lacuna little lake-small spaces between adjacent lamellae, osteocytes are located here
• Lamellae-Thin plate of bone, made up of collagen fibers, mineral salts and matrix
• Canaliculi-Minute canals which helps to connect adjacent lacunae. Lacunae are connected to one another and the Haversian canals through their canaliculi.
• Blood vessels of Haversian canals bring oxygen and nutrients and are distributed to different osteocytes through canaliculi.
  *The importance of Haversian system is the distribution of oxygen and nutrients to the deeply seated osteocytes of compact mammalian bone.

Bone Cells (Function and Location)

Collagen Fibers

• Collagen fibres are the most abundant protein in human body.
• It is kind of fibrous connective tissue.
• They function as a glue in the body, i.e. it holds together all the body structures.

Calcined or Decalcified Bone

• Bone maintain optimal level of calcium in the blood thus act as homeostatic organ.
• Calcined or Dried bone
  • Bone subjected to high temperature looses it’s organic matters and only minerals are left behind. The bone is called Calcined bone and process is called calcination.
• Decalcified or demineralized bone
  • Bone kept in the dil. HCl dissolves the inorganic part and organic part is left behind. The bone is called decalcified/demineralized bone matter (DBM).
  • DBM is used in the reconstruction of new bones and bony parts.

Bone: Ossification

• The formation of bone (ossification) occurs in one of two ways:
  • Intramembranous ossification - bone is formed by direct replacement of mesenchyme.
  • Endochondral ossification - cartilage model serves as the precursor of bone.

Questions

• Explain how each component of cartilage and bones are arranged to form a support system in humans.
• What is the significance of cartilage in the support system in humans?
• Though bones are harder, their capacity to heal is better than cartilages. Provide scientific reasons to support the statement.
• Explain the role of bone cells in bone remodelling

Think About:

• Why bone is able to resist tension and compression?
• How the differences between bone and cartilage can be accounted for in terms of the nature of the extracellular components present in cartilage and bone?
• How bone and cartilage obtain their nourishment?
• The different names for the cells in bone and cartilage.
• The different names for the outer layer of dense connective tissue.
• Differences between bone and cartilage.

Muscles

• The word muscle is derived from Latin word “musculus” meaning “Little Mouse”.
• Present approximately 639-650 skeletal muscles in normal human body.
• It is a specialized tissue of mesoderm origin of embryonic germ cells.
• The process of muscle formation is called myogenesis.
• The study of muscles is called as myology.

Muscle tissue

• Muscle tissue is a soft and contractile tissue made up of composed of specialized cells that have the special ability to contract and relax in order to produce movement of the body parts.
  Question: Explore on the functions of muscle.

Muscle Tissue (Features)

• It is highly and is well supplied with blood vessels.
• Muscles are made of elongated cells called muscle fibres or myocytes or sarcocytes
• Muscle fibres have covering outside the cell membrane called sarcolemma
• Sarcoplasm contains sarcoplasmic reticulum
• Thin myofibrils are arranged along the axis of muscle fibres
• Muscles are innervated with nerve fibres that brings impulses to contract and relax

Types of Muscles

1. Skeletal Muscle

• It is a type of striated muscle that is attached to the skeleton.
• Main function is to facilitate movement.
• Voluntary muscle as it is under the voluntary control of the nervous system.
• Skeletal muscles as it is attached to bones by bundles of collagen fibres called as tendons.
• Red or rough muscle
• It gets fatigue during strenuous work
• Helps in skeletal movement.

2. Non-Skeletal Muscle

• It also called Non-striated muscle due to absence of striation.
• Involuntary muscle as it is not under the control of the nervous system.
• Non-skeletal muscles as it is not attached to bones.
• White or smooth muscle due to smooth appearance
• Visceral muscle found in hollow internal visceral organ (digestive).
• It does not gets fatigue during strenuous work
• Helps in peristalsis movement

3. Cardiac Muscle

• It also called striated muscle
• Involuntary muscle
• Non-skeletal muscles as it is not attached to bones.
• Present in wall of heart.
• It does not gets fatigue during strenuous work
• Helps in heart movement

Muscle