L3 - Bone Development - Articulate H Flashcards
There are two types of ossification (aka) Osteogenesis: What are they?
- Intramembranous ossification
2. Endochondral ossification
What is bone embryologically derived from?
Mesenchyme
In which type of ossification do bone cells differentiate directly from mesenchymal cells to become osteoid?
Intramembranous ossification
Which type of ossification gives rise to flat bones found in the head and face at around week 8 of gestation?
Intramembranous ossification
Intramembranous ossification uses hyaline cartilage model precursor or not?
It does not
Endochondral ossification uses hyaline cartilage model precursor or not?
It does
Which type of ossification leads to the production of most short and long bones in the body?
Endochondral ossification
What week does endochondral ossification take place through gestation? when are they present in the long bones of the body?
Starts in week 6 and visible in long bones by week 12
What are the steps of intramembranous ossification?
- Development of the ossification center
- Calcification
- Woven bone and periosteum development
- Replacement of woven bone
What happens during the development of ossification center stage of intramembranous ossification?
mesenchymal cells cluster, they change into osteoprogenitor cells, and they become more and more basophilic as they become osteoblasts.
Osteoblasts secrete what?
Osteoid
What happens during the calcification stage of intramembranous ossification?
Calcium and other mineral salts are deposited around collagen fibers, giving rise to osteocytes
Osteoblasts that trap themselves in their calcifying osteoid are called what? and what do they sit in?
Osteocytes, lacunae
What happens during the woven bone and periosteum development stage of intramembranous ossification?
Primary bone is being made, growth along the surfaces, bone is woven together. The bone on the periphery condenses and forms periosteum
During woven bone and periosteum development what happens with the blood vessels that weave through the developing bone?
They become red bone marrow
What happens during the replacement of woven bone during intramembranous ossification?
Woven bone is replaced by lamellar bone forming compact and spongy bone
Flat bones are spongy or compact bone?
Both, they are spongy inside and compact on the outer layers
What are the characteristics of osteoblasts?
Cuboidal shape and very basophilic
Is woven bone organized or disorganized?
Disorganized
What tissue does bone develop directly from in intramembranous ossification?
Mesenchyme
Which of the following bones develops through intramembranous ossification?
a. Femur
b. Parietal bone
c. Phalanges
Parietal bone
What replaces mesenchyme during endochondral ossification?
Hyaline cartilage
What replaces hyaline cartilage during endochondral ossification?
Bone
What is the first step of endochondral ossification?
- Development of the fetal cartilage model
What is the second step of endochondral ossification?
- Bone collar forms around the diaphysis and cartilage of the shaft begins to calcify
What is the third step of endochondral ossification?
- Development of a primary ossification center in the diaphysis
What is the fourth step of endochondral ossification?
- Development of the secondary ossification centers
What is the fifth step of endochondral ossification?
- Retention of hyaline cartilage as the articular cartilage and the epiphyseal plate
What is the sixth (last) step of endochondral ossification?
- Epiphyseal plates ossify and form the epiphyseal lines
At which stage of endochondrial ossification is mesenchyme differentiating into chondroblasts that secrete matrix and produce the hyaline cartilage model?
- During development of the fetal cartilage model
During development of the fetal cartilage model what type of growth occurs because of the chondrocytes and activity of the chondroblasts on the surface?
Interstitial growth giving rise to the perichondrium
At which stage of endochondral ossification is the perichondrium becoming periosteum due to osteoblasts creating the first bone tissue to appear?
- Bone collar forming around the diaphysis and cartilage of the shaft beginning to calcify
What happens to oxygen and nutrients to the underlying cartilage as bone starts to develop?
The oxygen and nutrients are impeded upon because of the bone
What causes the chondrocytes to slowly die off?
The calcification of bone stops the chondrocytes from receiving nutrients via diffusion.
The absence of ______ causes the matrix to break down and calcified hyaline cartilage is created in the shaft.
Chondrocytes
Primary bone is eosinophilic or basophilic?
Primary bone is eosinophilic
Calcified bone is eosinophilic or basophilic?
Calcified bone is basophilic
What causes the development of bone marrow as well as creates primary ossification centers?
Blood vessels
Where is the main site for the primary ossification center ?
In the diaphysis
Where are the secondary ossification centers located?
In the epiphysis
What happens to chondrocytes in the development of secondary ossification centers?
They die off due to the compressing matrix, giving rise to spaces for blood vessels
What does hyaline cartilage on the end of the bone model become? What is the function?
It becomes articular cartilage for the cushioning of bones
The hyaline cartilage that remains between the diaphysis and the epiphysis has which function?
Acting as a growth plate for long bones
At the end of puberty what happens to the epiphyseal cartilage?
It is replaced by bone forming the epiphyseal line
What kind of ossification is used to lengthen long bone at the epiphyseal plate?
Endochondral ossification
What are the 5 zones of the hyaline cartilage in the epiphyseal plate?
- Resting cartilage
- Proliferating cartilage
- Hypertrophic cartilage
- Calcified cartilage
- Ossification
The zone of resting cartilage is closest to epiphysis or diaphysis?
Epiphysis
The zone of ossification is closest to epiphysis or diaphysis?
Diaphysis
Which zone are chondrocytes alone or in small groups? No mitosis is happening and the matrix is inactive.
Zone of resting cartilage
Which zone has chondrocytes undergoing mitosis creating matrix and causing the bone to lengthen?
Zone of proliferation (Zone of proliferating cartilage)
In which zone do chondrocytes undergo hypertrophy, cytoplasm accumulates glycogen, and the matrix is compressed/thinned?
Zone of hypertrophy (Zone of hypertrophic cartilage)
What happens to the chondrocytes in the zone of calcified cartilage as the cartilage calcifies?
They die because of the lack of nutrients through diffusion
In which zone do small blood vessels, osteoclasts, and osteoprogenitor cells inter the spaces previously occupied by chondrocytes?
Zone of ossification
What is the role of osteoblasts?
Laying down bone onto calcified cartilage spicules
What is the role of osteoclasts?
Breaking down and eroding new bone so secondary bone can be formed
Does the epiphyseal plate change width through the process of growth?
NO, the epiphyseal plate stays the same width
When during the epiphyseal plate development will the bone cells catch up with the chondrocytes?
During the closure of the epiphyseal plate
What type of growth is used to grow the bone width wise?
Appositional growth
During appositional growth Which should have a higher rate? osteoblasts or osteoclasts?
The rate of osteoblasts should equal the rate of osteoclasts at the end-steal layer
What is the process of removing old bone and laying down new bone?
Bone remodeling
Bone remodeling occurs where and when?
All over the body all the time
What percentage of bone is remodeled every year?
5-10%
Negative feedback loops, mechanical stresses, and gravity all play a key role in what process?
Bone remodeling
Which two hormones assist in the “When” bone remodeling will occur?
Parathyroid hormone and calcitonin
Parathyroid and calcitonin have a direct impact on which molecule?
Ca2+
What determines where remodeling will occur?
Mechanical stresses and gravity
