Unit 2: The skeletal system (Bone tissue) Flashcards
Describe what Bone is. What makes up the skeletal system?
Is an organ made up of several different tissue working together. The entire framework of bones and their cartilage constitutes the skeletal system.
What is osteology?
The study of bone structure and the treatment of bone disorder is referred to as osteology.
What are the six basic functions of the skeletal system?
- Support
- Protection
- Assistance in movements
- Mineral homeostasis (storage and releases)
- Triglyceride storage (yellow bone marrow)
- Bone cell production (red bone marrow)
How does the skeletal system support the body?
It serves as the structural framework for the body by supporting soft tissues and providing attachment points for the tendons of most skeletal muscles.
How does the skeletal system protect the body?
It protects the most important internal organs from injury.
How does the skeletal system assists in movement?
Most skeletal muscles attach to bones, when they contract, they pull on bones to produce movements.
How do bone tissues assist in mineral homeostasis?
Bone tissue stores several minerals like calcium and phosphorus, which contributes to the strength of bone. On demand, bone releases minerals into the blood to maintain critical mineral balances and to distribute the minerals to other parts of the body.
How does bone tissue store triglycerides?
Yellow bone marrow consists mainly of adipose cells, which stores triglycerides. This stored fats are potential chemical energy reserve.
How does blood tissue contribute in blood cell production?
In certain bones, red bone marrow produces RBCs, WBCs and platelets, a process called hemopoiesis. Red bone marrow consists of developing blood cells, adipocytes, fibroblasts, and microphages within a network of reticular fibers.
Whats the difference between new born and adult bone marrow?
In newborns, all bone marrow is red and is involved in hemopoiesis, with increasing age, much of the bone marrow changes form red to yellow.
What are the seven structures of the bone?
- Diaphysis
- Epiphyses
- Metaphysis
- Articular cartilage
- Periosteum
-Medullar cavity - Endosteum
Define diaphysis.
The bones shaft or body. The long cylindrical main portion of the bone.
Define Epiphyses.
The proximal and distal ends of the bone.
Define Metaphyses.
The region between the diaphysis and epiphyses. In a growing bone, each metaphyses contains an epiphyseal (growth) plate. When the bone stops growing, the cartilage in the plate is replaced by bone; the resulting bony structure is known as epiphyseal line.
Define what an epiphyseal (growth) plate is.
A layer of cartilage that allows the diaphysis of the bone to grow in length.
Define articular cartilage.
A thin layer of hyaline cartilage covering the parts of the epiphysis where the bone forms an articulation (joints) with another bone. Articular cartilage reduces friction and absorbs shock freely. Articular cartilage lacks a perichondrium and blood vessels, repair damage is limited.
Define periosteum. What is it composed of?
A tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage. Some periosteum also protects the bone, assists in fracture repair, helps nourish bone tissue, and serves as an attachment point for ligaments and tendons. Its composed of outer fibrous and osteogenic layer.
What is periosteum attached to?
It is attached to underlying bone by perforating fibers, thick bundles of collagen that extends from the periosteum into the bone matrix.
Define medullar cavity.
Also called marrow cavity. It is a hollow, cylindrical space within the diaphysis that contains fatty yellow bone marrow and numerous blood vessels in adults. This cavity minimizes the weight of the bone by reducing the dense bony material where it is least needed.
Define endosteum.
A thin membrane that lines the medullar cavity. It contains a single layer of bone forming cell and a small amount of connective tissue.
What is another name for bone and what does it contain?
Also called osseus tissue. Contains an abundant separated cells.
Describe the process of calcification.
As mineral salts are deposited in the framework formed by the collagen fibers of the extracellular matrix, they crystallize and the tissue hardens. It is initiated by bone building cells called osteoblasts.
What decides a bone hardness and flexibility?
A bones hardness depends on the crystallized inorganic mineral salts, a bones flexibility depends on its collagen fibers.
What are the four types of cells present in bone tissue?
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
Define Osteoprogenite cells.
Unspecialized bone stems cells derived from mesenchyme, they are precursor cells. These cells are the only bone cells to undergo cells division, developing into osteoblasts.
Define Osteoblasts.
Are bone building cells. They secrete collagen fibers and other organic components needed to build the extracellular matrix of bone tissue, they initiate calcification. Osteblasts surround themselves with the matrix, they become trapped and becomes osteocytes.
Define Osteocytes.
Mature bone cells, are the main cells in the bone tissue and maintain its daily metabolism. Osteocytes do not undergo cell division.
Define Osteoclasts.
These huge cells are concentrated in the endosteum. The cell releases powerful lysosomal enzymes and acids that digest the protein and mineral components of the underlying extracellular matrix. Osteoclasts help regulate blood calcium level.
Explain bone resorption.
The process by which the bones are absorbed and broken down by the body. The breakdown releases calcium and phosphorus into the blood stream. This breakdown occurs when the body has insufficient calcium.
Define compact bone tissue. What is is composed of?
The strongest form of bone tissue. Found beneath the periosteum of all bones and makes up the bulk of the diaphysis of long bones. It provides protection and support and resists the stresses produced by weight and movement. It is composed of repeating structural units called osteons.
Define concentric lamallae.
Circular plates of mineralized extracellular matrix of increasing diameter, surrounding a small network of blood vessels and nerves located in the canal. It’s what makes up the osteons.
Define lacunae.
Between concentric lamallae are small spaces called lacunae. Which contains osteocytes.
Define canaliculi.
Radiating in all directions from the lacunae are tiny canaliculi, which are filled with extracellular fluid.
Define interstitial lamellae.
The area between neighbouring osteons contain lamellae called interstitial lamellae. They are fragments of older ostoens that have been partially destroyed during done rebuilding or growth.
Define circumferential lamellae.
Around the entire outer and inner circumference of the shaft of a long bone. The circumferential lamellae directly deep to the peritoneum are called external circumferential lamellae. They are connected to the periosteum by perforating fibers. The circumferential lamellae surrounding medullary cavity are called internal circumfernetial lamellae.
Define spongey bone tissue.
Also referred to as trabecular. These do not contain osteons. Spongy bone is always located in the interior of a bone, protected by compact bone.
where are bone marrow stored and where blood cells are produced?
Spongey bone in the hip, ribs, sternum, vertebrae, and proximal ends of the humerus and femur is the only site where bone marrow and blood cells are produced.
Define periosteal arteries.
Small arteries accompanied by nerves, enter the diaphysis and supply the periosteum and outer parts of the compact bone.
Where are the three places blood are carried away from?
- One or two nutrient veins accompany the nutrient artery and exit through the diaphysis.
- Numerous epiphyseal veins and metaphyseal veins accompany their respective arteries and exit through the epiphyses and metaphyses.
- Many small periosteal veins accompany their respective arteries and exit through the periosteum.
Differentiate between arteries and veins.
Arteries take blood in. Veins carry blood out.
What is the process of bone formation called?
The process by which bone forms is called ossification or osteogenesis.
When are the four situations bone formation occurs?
- The initial formation of bones in an embryo and fetus.
- The growth of bones during infancy, childhood, and adolescence until their adult sizes are reached.
- The remodelling of bone
- The repair of fractures throughout the life.
What is embryonic skeleton composed of?
the embryonic skeleton are initially composed of mesenchyme in the general shape of bones.
Define intramembranous ossification.
Bones forms directly within mesenchyme, which is arranged in sheetlike layers that resemble membranes. Its the simpler of the two methods of bone formation.
How does the soft spot of the fetal skull formed?
They undergo intramembranous ossification.
Define endochondral ossification.
Bone forms within hyaline cartilage that develop from mesenchyme.
What process does bone formation undergo?
Most bones are formed by endochondral ossification.
What are the steps of intramembranous ossification?
- Development of the ossification centre..
- Calcification.
- Formation of trabecular.
- Development of the periosteum.
What are the steps of endochondral ossification?
- Development of the cartilage model.
- Growth of the cartilage model.
- Development of the primary ossification centre.
- Development of the medullary (marrow) cavity.
- Development of the secondary ossification centres.
- Formation of the articular cartilage and the epiphyseal plate.
What are chondroblasts and what do they do?
The chondroblasts secrete cartilage extracellular matrix, producing a cartilage model consisting of articulate cartilage.
What covers the cartilage model?
Perichondrium.
How are chondrocytes formed?
Once chondroblasts become deeply buried in the cartilage extracellular matrix, they are called chondrocytes.
Differentiate between interstitial growth and appositional growth.
- Interstitial growth chondrocytes secrete new matrix within the cartilage and this causes it to grow in length. Within the tissue.
- Appositional growth occurs when chondroblasts secretes new matrix along existing surfaces and this causes the cartilage expand and widen. Outer surface of tissue.
Define primary ossification centre.
The first area of a bone to start ossifying.
Define secondary ossification centre.
Develops in the epiphyseal ends
What are the two major events in growing bones in length?
- Interstitial growth of cartilage on the epiphyseal side of the epiphyseal plate.
- Replacement of cartilage on the diaphysial side of the epiphyseal plate with bone by endochondral ossification.
What are the four zones in the growing bone?
- Zone of resting cartilage
- Zone of proliferating cartilage
- Zone of hypertrophic cartilage
- Zone of calcified cartilage
Define the zone of resting cartilage.
The term ‘resting’ is used because the cells do no function in bone growth. Rather, they anchor the epiphyseal plate to the epiphysis of the bone.
Define zone of proliferating cartilage.
These chondrocytes undergo interstitial growth as they divide and secrete extracellular matrix. The chondrocytes in this zone divide to replace the ones that died at the diaphysial side of the epiphyseal plate.
Define zone of hypertrophic cartilage.
This layer consists of large, maturing chondrocytes arranged in columns.
Define zone of calcified cartilage.
The final zone is only a few cell thick and consists mostly of chondrocytes that are dead because the extracellular matrix around them has calcified. Osteoclasts dissolve the calcified cartilage, and osteoblasts and capillaries from the diaphysis invade the area. Bone matrix replaces the calcified cartilage the ‘new diaphysis/ that is firmly cemented to the rest of the diaphysis of the bone.
How does diaphysis increase in length and when does it stop?
The activity of the epiphyseal plate is the only way that the diaphysis can increase in length. When adolescence comes to an end, the epiphyseal plates close and the bone replaces all remaining cartilage.
Define epiphyseal line.
After the epiphyseal plate close during adolescence, it leaves a bony structure called the epiphyseal line, bone growth in length stops completely.
How do bone grow in thickness?
Bone can grow in thickness only by appositional growth.
Define remodelling of bone.
the ongoing replacement of old bone tissue by new bone tissue. It involves bone resorption and bone deposition.
Differentiate between bone resorption and bone deposition.
Bone resorption is the destruction of bone matrix.
Bone deposition is the formation of bone matrix.
What are the steps of bone resorption?
- During the process of bone resorption, an osteoclasts attaches tightly to the bone surface at the endosteum or periosteum and forms a leakproof seal at the edges of its borders.
- Then it releases protein digested lysosomal enzymes and acids into the sealed pockets.
- The enzymes digest collagen fibers and other organic substances while the acid dissolves the bone minerals.
- Working together, several osteoclasts carve out a small tunnel in the old bone.
- The degraded bone proteins and extracellular matrix minerals, enter the osteoclasts by endocytosis, cross the cell in vesicles, and undergo exocytosis.
- Now in the interstitial fluid, the product of bone resorption diffuse into nearby blood capillaries.
- Once a small area of bone has been resorbed, osteoclasts depart and osteoblasts move in to rebuild the bone in that area.
What are the three factors affecting bone growth and bone remodelling?
- Minerals
- Vitamins
- Hormones
Explain how minerals affect bone growth and bone remodelling.
Large amounts of calcium and phosphorus are needed while bones are growing. Also small amounts of magnesium , fluoride, and manganese. These minerals are also necessary during bone remodelling.
Explain how vitamins affect bone growth and bone remodelling.
Vitamin A stimulates activity of osteoblasts. Vitamin C is needed for synthesis of collagen, the main bone protein. Vitamin D helps build bones by increasing the absorption of calcium from foods in the gastrointestinal tract. Vitamin K and B12 are also needed for synthesis of bone proteins.
Explain how hormones affect bone growth and bone remodelling.
- Hormones most important to bone growth are the insulin like growth factors (IGF). IGFs stimulate osteoblasts, and promotes cell division, at the epiphyseal plate and in the periosteum, and enhances synthesis of the proteins needed to build new bone.
- Thyroid hormones also promote bone growth by stimulating osteoblasts.
- At puberty, the secretion of hormones known as sex hormones causes a dramatic effect on bone growth.
What are sex hormones?
The sex hormones includes estrogen (Produced by the ovaries) and androgens such as testosterone (Produced by the testes). These hormones are responsible for increased osteoblasts activity, synthesis of bone extracellular matrix, and the sudden ‘growth spurt’ that occurs. Sex hormones (especially estrogen) shuts down growth at the epiphyseal plate.
What is the bones role in calcium homeostasis?
Bone is the body’s major calcium reservoir. One way to maintain the level of calcium in the blood is to control the rates of calcium resorption from bone into blood and of calcium deposition from blood to bone. Both nerve and muscle cells depends on the stable level of calcium ions to function properly. Small changes in the calcium ion concentration may be fatal.
How is calcium exchange regulated?
Calcium exchange is regulated by hormones, the most important of which is the parathyroid hormone (PTH). This hormone increases blood calcium levels.
How does the parathyroid hormone regulate calcium exchanged?
- PTH secretion functions via a negative feedback system.
- PTH also acts on the kidneys to decrease loss of calcium in the urine.
- PTH stimulates formation of calcitriol, this hormone promotes absorption of calcium from foods in the gastrointestinal tract in the blood. - When blood calcium rises above normal, the thyroid glands secrete calcitonin (CT).
- CT inhibits activity of osteoclasts, speeds blood calcium uptake by bone, and accelerate calcium deposition into bone.
How many named bones are there in an adult human skeleton?
206.
What is the main difference between adult human skeleton and infant human skeleton?
Human skeletons has 206 named bones, but infants have more bones, these bones fuse together later in life.
What are the two principal division of an adult skeleton?
Axial skeleton and appendicular skeleton.
What does the appendicular skeleton consists of?
Upper and lower limbs, plus the bones forming the girdles that connect the limbs to the axial skeleton.
What are the five types of bones?
- Long bones
- Short bones
- Flat bones
- Irregular bones
- Sesamoid bones.
Describe what long bones are.
Consists of a shaft and an epiphyses and are slightly curved for strength. Long bones mostly consists if compact bone tissue in their diaphyses but have considerable amount of spongy bone tissue in their epiphyses.
Where are long bones located?
- Femur (thigh bone)
- Tibia and fibula (leg bone)
- Humerus (arm bone)
- Ulna and radius (forearm)
- Phalanges (figners and toes)
Describe what short bones are.
Somewhat cube shaped. They consists of spongy bone except at the surface, which has a thin layer of compact bone.
Where are short bones located?
- Most carpal bones (wrist)
- Most tarsal bones (ankles)
Describe flat bones.
Generally thin and composed of two nearly parallel plates of compact bone tissue. Flat bones afford considerable protection and provide extensive area for muscle attachments.
Where are flat bones found?
- Cranial bones
- The sternum (chest bone)
- Ribs
- Scapulae (shoulder blades)
Describe what irregular bones are.
Have complex shapes and cannot be grouped into any other bone types. They vary in the amount of spongy and compact bone present.
Where are irregular bones found?
- Vertebrae (back bones)
- Hip bones
- Some facial bones
- Calcaneus (heel bone)
Describe what sesamoid bones are.
- Develops in certain tendons where there is considerable friction, tension and physical stress such as the palms and soles.
- They are not always completely ossified.
- Sesamoid bones protects tendons form excessive wear and tear, and they often change the direction of pull of a tendon.
What are sutural bones?
An additional type of bone classified by location rather than shape. They are small bones located in sutures (joint) between cranial bones.
What are surface markings?
Most are not present at birth but develop in response to certain forces and are not most prominent in the adult skeleton.
What are the two major types of surface markings? And describe them
Depressions and openings - allows the passage of soft tissues or form joints
Processes - projections or outgrowths that either helps form joints or serve as attachment points for connective tissue.
How many bones does the skull contain?
22 bones.
What are the two categories skull bones are grouped in?
- Cranial bones
- Facial bones
Describe what cranial bones are. What are the bones called?
- Encloses and protect the brain.
- There are 8 in total; the frontal, 2 parietal bones, 2 temporal ones, the occipital bone, the sphenoid and ethmoid bones.
Describe what facial bones are. What are the bones called?
There are 14 facial bone. 2 nasal bones, 2 maxilla, 2 zygomatic bone, and mandible, 2 lacrimal bones, 2 palatine bones, 2 inferior nasal conchae, and the vomer.
What other smaller cavities does the skull have?
- Nasal cavity
- Orbits (eye sockets)
- Paranasal sinuses
- Middle ear cavities
Describe what the frontal bones are.
Forms the forehead, and the roofs of the eye sockets. Soon after birth, the left and right sides of the frontal bone are united by the metopic sutures, which will usually disappear with age.
Describe what the parietal bones are.
The two parietal bones form the greater portion of the sides and roof of the cranial nerve. The internal surfaces of the parietal bones contain many protrusions and depressions that accomodate the blood vessels supplying the dura mater.
What is a temporal squama? And how is the zygomatic process related? And together what do the form?
The temporal squama are thin, flat part of the temple. Projecting from the inferior portion of the squama is the zygomatic process which articulates (forms a joint) with the temporal process of the zygomatic (cheek) bone. Together they form the zygomatic arch.
What makes up the tempomandibular joint (TMJ)?
A socket called the mandibular fossa articulates with the articular tubercle and forms the TMJ.
What forms the occipital bone?
Forms the posterior part and most of the base of the cranium.
Describe what a foramen magnum is.
Means large hole. The medulla oblongata connects with the spinal cord within this foramen, and the vertebral and spinal arteries also pass through it.
Describe what the occipital condyles are.
Oval processes with convex surfaces on either side of the foramen magnum.
Which joint allows us to nod our head ‘yes’?
The atlanto-occipital joints.
Describe what the sphenoid bone is.
This bone is called the keystone of the cranial bones, because it articulates with all the other cranial bones which holds them together.
What is the space in the sphenoid bone called?
The sphenoidal sinus, which drains into the nasal cavity.
What are the bones in the axial skeleton?
- Skull
- Hyoid bone
- Auditory ossicles
- Vertebral column
- Thorax
What are the bones in the appendicular skeleton?
- Pectoral girdle
- Upper limbs
- Pelvic girdle
- Lower limbs
Describe what the mastoid bone is.
Contains mastoid air cells that communicate with the hollow space of the middle ear. Ear infections that spread to these cells cause mastoiditis.
Describe what the palatine process of maxilla is.
The union of the maxillary bones normally is completed before brith. If this fails, this forms a cleft palate.
Describe what the hypophyseal fossa is.
This fossa contains the pituitary gland.
Describe what the foramen rotundum is.
The maxillary branch of the trigeminal nerve pass through here.
Describe what the ethmoid bone is.
Forms part of the anterior portion of the cranial floor, the medial wall of the orbits, the superior portions of the nasal septum, and most of the side walls of the nasal cavity.
What is the nasal septum?
A partiton that divides the nasal cavity into right and left side.
Describe what the cribriform plate is.
It contains the olfactory foramina which the olfactory nerve pass through.
What is the mastoid process?
The point of attachment for several neck muscles.
What goes through the internal auditory meatus?
Facial nerves and vestibulacochlear nerve passes through here.
Describe what the petrous portion is.
This houses the internal and middle ear, which are the structures that are involved in hearing and equilibrium.
Describe what the nasal bones are.
They are paired and small, flattened, rectangular shaped bones that form the bridge of the nose. The major structural portion of the nose consists of cartilage.
Describe what the lacrimal bones are.
The paired lacrimal bones are thin and roughly resembles a fingernail in size and shape. These bones, the smallest bones of the face, are posterior and lateral to the nasal bones and for a part of the medial wall of each orbits.
What is a lacrimal fossa?
The lacrimal bones each contain a lacrimal fossa, that houses the lacrimal sac, a structure that gather tears and passes them into the nasal cavity.
Describe what the palatine bones are.
The two L shaped palatine bones form the posterior portion of the hard palate, part of the floor and lateral wall of the nasal cavity, and a small portion of the floors of the orbit.
Describe what the inferior nasal conchae are.
The two inferior nasal conchae are separate bones, and not part of the ethmoid bones. The nasal conchae increase the surface area of the nasal cavity and helps swirl and filter air before it passes into the lungs.
Which bone is involved in the sense of smell?
Only superior nasal conchae are involved in the sense of smell.
What is a vomer?
A roughly triangular bone on the floor of the nasal cavity that articulates superiorly with the perpendicular plate of the ethmoid bone and inferiorly with both the maxillae and palatine bones.
Describe what the maxillae is.
Unite to form the upper jaw bone. They articulate with every facial bone except for the mandible.
What is the hard palate?
The bony roof of the mouth, this separates the nasal cavity from the oral cavity.
Describe what the zygomatic bones are.
More commonly known as cheek bones. They articulate with the frontal, maxilla, sphenoid, and the temporal bones.
Describe what the mandible is.
Also called the lower part of the jaw. It is the largest, strongest facial bone. It is the only moveable skull bone (except for the auditory ossicles).
How many bones does the orbit consists of?
Seven bones.
Define foramina.
Openings for blood vessels, nerves, or ligaments.
Describe what sutures of the skull are. Describe the difference between adults and infants.
An immovable joint that holds most skull bones together. Sutures in the skulls of infants and children are moveable and functions as important growth centres in the developing skull.
What are the four most prominent sutures?
- Coronal sutures
- Sagittal suture
- Lambdoid sutures
- Squamous sutures
