September 19, 2011
Lecture 3 – Epithelia Part 3 & Connective Tissue Part 1
Carcinoma refers to a malignant tumor that arises from epithelia specifically
Malignant tumors are capable of metastasizing, travelling from the primary source tissues
to other tissues of the body (ex. skin tumor travelling to the brain).
Benign tumors don’t metastasize. They can grow uncontrollably as well but don’t spread.
Carcinoma is malignant tumors that arise from epithelium. Adenocarcinoma arises from
glandular epithelium. Malignant tumors can arise from other tissues as well; sarcoma
(arising from muscles, blood vessels and bones), lymphoma (arises from lymphoid tissue)
and leukemia (arises from white blood cells).
Squamous cell carcinoma example – there is a distinct line that separates the epithelium
and connective tissue, but it seems to be blurred because the epithelium has now invaded
the underlying tissue.
Connective Tissue (Ordinary Connective Tissue and Cartilage)
Tissues are composed of cell and cell products. Connective tissues (everything from
adipose, cartilage, tendons, bones) have fewer cells and the bulk of the tissue is cell
product (acellular material; the cell matrix, stuff between the cells).
Matrix consists of fibers (protein) and ground substance (goo in between).
Characteristics of matrix determine its properties and functions. It is the matrix that
makes bones hard, it is the matrix that makes cartilage rubbery, matrix that makes loose
connective tissue flexible support.
The matrix is produced by the cells of the connective tissue.
Cells create protein fibers and organic ground substances and secrete them in their
Cells are specialized, fibro- is ordinary connective tissue, chondro- is cartilage and osteo-
is bone tissue.
Connective tissues consists of cells and matrix. Matrix are made up of fibers and ground
substance. There are collagen and elastic fibers. There are tissue fluid and organic
molecules that make up the ground substance. Proteoglycans and adhesive glycoproteins
are the organic molecules.
Tendon connects a muscle to a bone. Ligament connects bone to bone. Muscles contract
and shorten to generate tension. When the muscle shortens, the bone moves. That’s only
if the bone doesn’t give and it requires the protein to be inelastic.
Collagen is a major component of tendons. It is inelastic and resists tension (great tensile
strength). Tendons are made up of bundles of collagen fibers. Fibers are made up of
smaller components called fibrils. There are over 20 types of collagen, based on amino acid sequences. Collagen are
fibrillar which forms long structures, and their synthesis is a multistep process.
Preprocollagen makes the procollagen, which makes the tropocollagen, which makes the
fibrils which forms the fibers.
Alpha chains (mRNA) are transferred to the cytosol. The alpha chains are synthesized
within the rough ER (preprocollagen) and it is assembled into an alpha helix. Registration
peptides are important because it maintains the solubility of procollagen. Procollagen is
transferred to the Golgi and it is packaged into secretory vesicles and is associated with
microtubules, transferred to the cell surface. They are then released and registration
peptides are removed, they are now called tropocollagen, which only exists
extracellularly. Tropocollagen spontaneously aggregates and forms collagen fibrils. There
are covalent cross-links that make the tropocollagen very strong and resist tens