UNIT ONE: LECTURE CONTENT

QUIZLET WITH ALL U1 LECTURE CONTENT   (more in depth and has all vocab terms)

https://docs.google.com/document/d/12ilcHE4gZmy-LAPBL0JvtK_0qdQxsEGRsQeDpDAYB2k/edit?tab=t.0

-ABOVE IS THE GOOGLE DOC WITH SCANNED IMAGES OF MY NOTES FOR THE SKELETAL SYSTEM

-(Quite in depth because this content was a bit harder for me to comprehend!)

For a living person, list at least eight (8) of the tissue types present somewhere in the femur bone (as an organ). Indicate at least one example location where each type would be found in the bone.

-Adipose connective tissue: found in yellow bone marrow of long bone.

-Reticular CT: found in red bone marrow

-Osseous tissue: can be found in the entire femur but mostly the diaphysis of the femur

-Dense irregular connective tissue: outer layer of periosteum

-Spongy bone tissue: epiphysis (proximal or distal end)

-Adipose tissue: in the yellow bone marrow in the medullary cavity

-Compact Bone tissue: Collar on the outside of the diaphysis

Describe the process of intramembranous ossification (to the level of detail described in lecture). Where does the process occur? What is the starting tissue called? How does ossification occur?

Bone Formation During Fetal Development

**Ossification** (the process of bone formation) occurs during fetal development in two main ways: **Intramembranous Ossification** and **Endochondral Ossification**.

Intramembranous Ossification

- **Location**: This process primarily involves the bones of the skull and the clavicle.

- **Process**:

  1. It begins in a type of loose connective tissue called **mesenchyme**.

  2. Mesenchymal cells receive hormonal signals that prompt them to secrete a substance known as **osteoid**, which is the initial bone matrix. This signaling also encourages blood vessel growth that brings calcium to help the osteoid harden into **hydroxyapatite**.

  3. These mesenchymal cells transform into **osteoblasts**, which cluster together to create an **ossification center** where they begin laying down bone matrix.

  4. As more osteoblasts are formed, they become encased in the bone matrix and turn into **osteocytes**.

  5. Blood vessels continue to infiltrate the area, while cells called **osteoclasts** help hollow out spaces around the trabecular structure of the spongy bone. 

  6. The resulting spaces within the spongy bone get filled with **red bone marrow**.

  7. The flat bones of the skull exhibit a unique structure, featuring two layers of compact bone with a layer of spongy bone sandwiched in between.

Endochondral Ossification

- **Location**: This method forms the majority of the fetal skeleton, with the exception of the skull and clavicle, which initially develop as **hyaline cartilage**.

- **Process**:

  1. Chondrocytes (cartilage cells) receive hormonal signals prompting them to calcify and ultimately die.

  2. This death allows **osteoblasts** to migrate to the area and form the **primary ossification center** in the bone's shaft (diaphysis). Here, they secrete osteoid, but they wait for incoming calcium to allow for the hardening process.

  3. As blood vessels grow into the area, they deliver calcium that helps the osteoid transition into hydroxyapatite.

  4. **Secondary ossification centers** develop in the bone's ends (epiphyses), leading to the ossification of these regions.