Skeletal System Flashcards
List the functions of the skeletal system with a short description
- Support (bones support the soft tissues and provide attachment sites for muscles, making them a structural framework for the body)
- Protection (internal organs are protected by the bones)
- Assist in movement (assis skeletal muscles)
- Mineral homoestasis (bones store and release several minerals like calcium and phosphorus)
- Production of blood cells (homeopoiesis occurs in red bone marrow)
- Triglyceride storage (yellow bone marrow in adult bones)
What are the types of bone shape?
Long bones, short bones, flat bones and irregular bones
Describe long bones and give examples
They consist of a shaft with two ends, like the femus, the humerus, the phalanges
Describe short bones and give examples
They are cube like and exist in wrists (carpals) and ankles (tarsals)
Describe flat bones and give examples
they are thin and usually curved, like skull bones and ribs
Describe irregular bones and give examples
They do not fit in any other category like vertebrae or hip bones
What are the various parts of a long bone?
The diaphysis, the epiphyses, the metaphyses, the hyaline cartilage, the periosteum, the endosteum, the marrow cavity, the red marrow, the yellow marrow
What is the diaphysis?
The shaft of the long bone
What are the epiphysis?
The ends of the bone
What are the metaphyses?
The areas between the epiphysis and the diaphysis that include the epiphyseal plates in growing bones
What is hyaline cartilage and where is it located?
Flexible gel-like cartilage at the ends of long bones to protect from shocks
What is the periosteum and what is its use?
A connective tissue that covers the surface of the bones. It contains osteogenic cells, it protects bones, assists in fracture repair, helps nourish bone tissue and serves as attachment point for ligaments and tendons
What is the marrow cavity?
The space within the diaphysis
What is red marrow and where is it located?
The site of homoepoesis, in the epiphyses and metaphyses
What is yellow marrow and where is it located?
The site of triglyceride storage and in the diaphysis
What is the endosteum?
The lining of medullary cavity
What are the principal bone cells and their function?
osteoprogenitor (osteogenic cells, stem cells that differentiate into osteoblasts), osteoblasts (bone building cells that produce matrix), osteocytes (mature bone cells), osteoclasts (break down bone tissue)
What is bone matrix made of ?
inorganic salts like hydroxyapatite and calcium carbonate, and collagen fibers.
What is the process of calcification?
When the inorganic salts are deposited in the framework of collagen fibers.
What is the use of minerals in the bone matrix, and what is the use of collagen?
The salts confer the hardness, and the collagen the tensile strength
What is the unit of compact bone ?
Osteons, or harvesian systems
What are the components of osteons?
blood vessels, lymphatic vessels, nerves, osteocytes in the calcified matrix
What is cancellous bone made of ?
traberculae and red bone marrow
What are traberculae?
columns or beams of bones in the spongy bones
Where is spongy bone found? What is its use?
In most of the structure of short, flat and irregular bones, and in the epiphyses of long bones. It’s light, and supports and protects the bone marrow.
What is ossification, or osteogenesis?
The process of bone growing
What are the two types of ossification?
Intramembraneous ossification and endochondral ossification
What is the general definition of intramembraneous ossification, and which bones does it produce?
It is when the formation of bone occurs directly from mesenchymal cells (undifferentiated connective tissue cells), and it makes the skull and mandibles
What is the general definition of endochondral ossification and what bones does it produce?
It is when the bones form from hyaline cartilage, and it produces most bones in the body
Desribe the steps involed in intramembraneous ossification
- Mesemchymal cells differentiate into osteoblasts, which cluster together, creating the center of ossification.
- The osteoblasts generate osteoids, the uncalcified matrix.
- The matrix gets calcified, which traps osteoblasts, turning them into osteocytes.
- These organize into trabercular, forming structures around blood vessels forming spongy bones
- The mesenchymal cells outside form periosteum , which them forms an inner layer of osteoblasts, which will produce compact bone around the spongy bone. The blood vessels become red marrow.
Describe the steps involved in endochondral ossification
- Mesenchymal cells differentiate into chondroblasts, which makes chondrocytes, which makes a cartilage scaffold with a perichondrium layer, in the shape of the bone.
- The middle chondrocytes swell, and it starts calcifying the matrix. The end parts of the matrix are not calcified.
- The middle part of the shaft becomes vascularized, which changes the perichodrium to the periosteum. The calcified matrix prevents nourishement of the chondrocytes , and lead to chrondocyte death.
- Vascularization reaches the dead cells, creating the primary center of ossification. There is a mix of calcified cartilage and calcified bone from the the osteoblasts form the periosteum.
- The osteoclasts destroy the center cavity to create the medullary cavity and the osteoblasts create bone around it (osteoids, which become calcified, and create traberculae, then compact bone)
- Secondary ossification centers form in the epiphyses.
Explain longitudinal bone growth
It is a type of endochondrial ossification. The epiphyseal growth plate changes into bone, until it becomes the epiphyseal line, which indicates the bone has stopped growing.
Explain diameter growth in bone
It is intramembraneous growth from the periosteum by making osteoblasts while the osteoclasts resorb bones in the endosteum in the spongy bone.
What is remodeling?
The fact that bone constantly breaks down broken or unused bones with osteoclasts, and rebuilds it with osteblasts.
What are the minerals needed for bone growth?
Calcium, magnesium and phosphorus
What are the vitamins needed in bone growth?
Vitamin A, B12, C, D and K
What are the the important hormones for bone growth during childhood?
insulin-like growth factors, stimulated by the human growth hormone
What hormones are necessary for bone growth in general?
Thyroid hormones, insulin and calcitonin
What hormones stimulate sudden growth during puberty?
estrogen and testosterone
What is osteoporosis?
A disease due to aging where the bone resorption is greater than bone formation, which results in weakening of the bones.
What systems need a balanced calcium level?
Skeletal cardiac, nervous.
What calcium level do we need?
10mg/L
What happens when there is an increase in calcium levels?
- The thyroid gland releases calcitonin
- Osteoclasts activity is inhibited
- Calcium reabsorption in the kidneys is decreased
- The calcium level in the blood decreases
What happens when calcium levels decrease?
- The receptors in the parathyroid gland release parathyroid hormones (PTH)
- It stimulates osteoclasts to release more calcium
- It stimulates the kidneys to reabsorb more calcium
- Calcium is absorbed from the intestines through vitamin D synthesis
- Calcium in the blood increases.
What are thw two divisions of the skeletal system and what do they comprise?
axial (skull, thoracic cage and vertebral column) and perpendicular (all other bones)
What are the main bones in the skull?
cranial portion and facial portion
What are the main bones in the pectoral girdle?
clavicle, scapula
What are the main bones in the thoracic cage?
sternum, ribs
What are the main bones in the upper limb?
humerus, radius, ulna, carpals, metacarpals, phalanges
What are the main bones in the lower limb?
femus, patella, tibia, fibula, tarsals, metatarsals, phalanges
What are the main bones in the pelvic girdle?
hip bones
Describe the structure of an osteon
Osteons are made of concentric lamellae, that have various orientations of collagen fibers to resist torsion. In the middle, the haversian canal contain blood vessels, nerves and lymphatic vessels. In between the lamellae in the bone matrix are small spaces called lacunae, in which we find trapped osteocytes. The osteocytes recieve nutrients through small canals in between lacunae called canaliculi.
