Lecture 1 Connective Tissues Flashcards
Functions of connective tissues
- Structural support
- protection/padding of internal organs (smooth surface to glide)
- defense against infection or disease
- diffusion of nutrients and wastes
- storage of energy and nutrients
Connective tissue vs epithelial tissue
Connective tissue
- cells lack basement membrane
- extracellular material
- highly vascular
- completely surrounded by other tissues
epithelial Tissue
- Cells have basement membrane
- little or no extracellular material
- avascular
- free surface
2 connective tissue subtypes
Connective tissue proper, specialized connective tissue
Types of connective tissue proper
Loose connective tissue, Dense connective tissue
Specialized connective tissue
Adipose tissue, cartilage, bone, blood
Components of connective tissue
Cells: derivatives of undifferentiated mesenchymal cells, derivatives of hematopoietic cells
Extracellular matrix: Fibers, ground substance
What are progenitor cells
Descendants of stem cells that then further differentiate to create specialized cell types
What is the origin of connective tissue cells
Progenitor cells in the embryonic mesoderm (mesenchyme)
Properties of progenitor cells
- cell division (proliferation)
- differentiation into many cell types (pluripotent)
Types of progenitor cells
- hematopoietic stem cells: form blood cells
- undifferentiated mesenchymal stem cells: form other cell types in the body
Types of stem cell division
- symmetric stem cell renewal: creates 2 stem cells, or creates two differentiated cells
- asymmetric stem cell renewal: creates on stem cell and one differentiated cell
Why are stem cells important?
Necessary for normal tissue development and for repair of damaged tissue
-New technologies: experimentally reprogram differentiated somatic cells into inducible pluripotent stem cells, and then use these stem cells to build new organs with the assistance of 3D printers
Hematopoietic stem cells can differentiate into which kinds of cells found in connective tissue
-plasma cell, B lymphocyte, Free macrophage, mast cell, neutrophil, eosinophil
Undifferentiated mesenchymal cells can differentiate into which cell found in connective tissue
Fibroblasts
Fixed or resident cells
Originate and remain in the CT for a long time
Transient or wandering cells
Originate in the bone marrow or lymph glands, enter CT for a short time
General function of Fixed/resident CT cells
Structural support
Types of resident CT cells
- Fibroblasts (active)
- fibrocytes (inactive)
Fibroblast cells function and features
FXN: synthesize and secrete components of the extracellular matrix
Features: oval or spindle shaped, many long cellular processes (less processes as they mature)
Transient CT cells origin and function
-differentiate from hematopoietic stem cells, migrate into CT from blood or lymph
FXN:
- migrate into CT from blood or lymph
- fight infection and disease
- assist tissue remodeling and repair
Types of transient CT cells
Macrophages, lymphocytes, plasma cells, leukocytes, eosinophils, neutrophils, mast cells
Macrophage origin
Monocytes in the circulating blood
Macrophages function and features
FXN: phagocytosis of foreign substances and dead or damaged cells/debris, secretion of factors (cytokines and chemokines), that stimulate inflammation, cell migration, blood vessel development, antigen recognition, lymphocyte differentiation
Features: Pseudopodia, lysosomes, phagosomes
Phagocytosis by macrophages (steps)
- Detection of and movement toward foreign material
- Engulfment of material into a phagosome
- Fusion of phagosome with a digestive vacuole
- Breakdown of material
- Exocytosis of residual debris
Lymphocyte origin
Hematopoietic stem cells
Lymphocytes function and features
FXN: recognize antigens by producing antibodies that act as surface receptors to recognize antigens
Features: large dense nucleus, relatively small amount of cytoplasm
Plasma cells Origin
B lymphocytes that have undergone proliferentiation and differentiation
Plasma cells function and features
FXN: synthesize and secrete antibodies (immunoglobulins) into the circulation
Features: rough endoplasmic reticulum (lots) for protein synthesis, Golgi apparatus for large modification of proteins, nucleus (eccentric, and cartwheel pattern of heterochromatin)
Two types of leukocytes in connective tissue
Eosinophils and neutrophils
Eosinophils origin
Hematopoietic stem cells
Eosinophils function and features
FXN: Kill parasitic worms
Features: bi-lobed nucleus, cytoplasm contains large eosinophilic granules
Neutrophils origin
Hematopoietic stem cells
Neutrophils function and features
FXN: kill bacteria
Features: multi-lobed nucleus, cytoplasm contains very small neutral stained granules
Mast cells origin
Precursors in the bone marrow
mast cells function and features
FXN: initiate local inflammatory response, participate in development of allergies Features: large oval shape, plasma membrane contains receptors for the immunoglobulin E (IgE) class of antibodies , basophil is granules (heparin, histamine)
Inflammation definition
Calor: Heat
Dolor: Pain
Rumor:Redness
Tumor: Swelling
Inflammation cause
Cytokines, chemokines and other inflammatory mediators induce changes in local blood vessels, cells, and tissue fluid
Cytokines
Secreted proteins that influence the behavior of other cells that have receptors for these cytokines
*mediators of host response to infection, trauma, and immune response
Chemokines
Secreted proteins that attract other cells, which exhibit specific receptors, from the bloodstream
Inflammation, role of transient CT cells
- Bacteria (or other pathogens) stimulate macrophages to release cytokines and chemokines
- Mast cells release histamine, which increases vascular diameter and permeability, causing increased local blood flow and leakage of fluid into the tissue
- Neutrophils, lymphocytes and other immune cells migrate into the tissue releasing inflammatory mediators that cause pain
