Anatomy and Cell Biology 3309 Lecture Notes - Lecture 7: Eosinophilia, Fibroblast, Ground Substance
19 Aug 2019
School
Department
Professor
ACB 3309 Lecture 7 (CT & its derivatives)
Connective Tissue II: The Cells
Cells of Connective Tissue Classification
Fibroblasts
Function: Make all fibres and ground substance found in connective tissue
Structure
o 15um long
o Star-shaped
o Large cell body; rest of the cell thins out and goes between fibres
▪ Usually only see the elongated nucleus
o Pale nucleus with prominent nucleolus
o Elongated cytoplasm
▪ Cytoplasmic extensions are gonna intermingle with the collagen fibres
▪ As a result, it’s gonna be hard to identify a fibroblast as a whole, under LM
LM (H&E)
o Purple = nucleus
o A lot of pink & eosinophilia
o Collagen – very eosinophilic
Collagen
Nucleus of
green fibroblast
Cytoplasmic
extensions
Mature cell is called a fibrocyte
Endothelial Cells and Pericytes
Endothelial cells:
o Flattened cells (look like simple squamous epithelium) lining the inside of blood vessel
o Can be fenestrated (holes) to allow passage of small molecules in and out of blood vessel
o Or can be continuous
o Are anchored to one another through fascia occludens junctions
o Capillaries are so small that the lumen only has space for 1 RBC → identifying feature
Just outside the endothelial cells is the basement membrane – pale stained lines b/w E & P cells
o “Like saran wrap wrapped around the endothelial cells”
Pericytes
o Line the outside of capillaries and venules
o 12um long
o Function:
▪ Can become phagocytic and present antigens
▪ Adult mesenchymal cells – can differentiate into other cell types (e.g., endothelial cells,
fibroblasts, muscle)
• E.g., coronary artery disease – in early stages, the endothelial cells become
damaged and get fatty streaks in them
o Pericytes can differentiate into endothelial cells to heal vessel wall
N
N
Nuclei of
endothelial cells
Macrophages
• Function – phagocytose foreign particles – like pacman
o Lots of lysosomes and residual bodies
• Kinda part of the immune system
• Formed in the bone marrow (a type of hematopoietic tissue)
• Different names in different tissues:
o “Monocyte” – in Blood
o “Macrophage” in the tissues
▪ Specifically, “histiocytes” in connective tissue
o “Microglia” – in CNS
o “Kupffer cell” – Liver
o “Osteoclast” – Bone
o “Langerhans’ cell” – Epidermis
• Oddly shaped nucleus
Lymphocytes
Function: part of the immune system
EM: Large, round nucleus with little surrounding cytoplasm
o If the cell is activated and must produce antibodies, the nucleus changes from heterochromatic
to euchromatic
LM: purple – they just look like floating nuclei
RBC
Capillary
*Note*: in LM image, can’t
tell the difference b/w
endothelial cell and pericyte
Cross section of capillary
-very eosinophilic dot = RBC
-basophilic dot = nucleus of
endothelial cell
N
Primary
Lysosome
Secondary
Lysosome
-in the
process of
digesting
something
