Lecture 1 Connective Tissue Flashcards
Is connective tissue exposed to the outside?
No. CT is never normally exposed to the outside. It is always covered by an epithelium
Are CT cells in contact with one another?
Connective tissue is made up of individual cells scattered within an extracellular matrix, which is a gel- like substance that also has protein fibers in it.
Roles; carries O2, CO2, nutrients and wastes
What is the ECM?
- A gel-like substance that has protein fibers in it.
- Carries O2, CO2, nutrients and wastes.
What are the types of connective tissue?
- Embryonic CT
- Adult CT (adult connective tissue is fibrous; it can be loose, dense irregular and dense regular)
- Special: adipose, cartilage, bone and hematopoietic.
Fx of connective tissues
- Framework for the body
- Protection
- Supports and interconnects other tissues
- Stores NRG
- Transports fluids, cells and dissolved chemicals throughout the body
- Defends against microorganisms
What type of cells are found in connective tissue?
- Fibroblasts
- Mesenchymal cells
- Adipocytes
- Chondro[cytes]
- Osteo[blasts]
- Hematopoietic stem cells
What are fibroblasts?
Fibroblasts make up a majority of the ECM. They make
- Collagen
- Proteoglycans
- Glycoproteins
What are mesenchymal cells?
They are connective tissue stem cells.
What are adipocytes?
They store and release fat.
What are chondrocytes?
Make cartilage
What are hemapoetic stem cells?
make RBCs and immune cells
Describe the fibrous component of the extracellular-matrix.
Fibrous part of the ECM is made up of:
- Collagens (type 1 is the most common), which resists tension
- Elastin (a stretchable fiber made up of tropoelastin, fibulin-1 and fibrillins 1 and 2)
- Reticular fibers that form a supportive meshwork.
Describe type 1 collagen fibers?
collagen fibers that are aligned and crosslinked to increase tensile strength
What is Scurvy?
Scurvy is a vitamin C deficiency.
Vitamine C is a cofactor needed for collagen to cross-link. Thus, people with scruby often have weak CT.
Ehlers Danlos Syndrome
Collagen is made abnormally, causing it to be WEAK. Thus, the CT is weak.
What is Marfans Syndrome?
Marfans sydrome is an autosomal dominant syndrome where elastin is weak due to a mutation in fibrillin-1.
This targets ocular, skeletal and cardiovascular systems. Patients tend to have cardiovascular anomalies, and tend to be tall with long arms and legs.
Incidence of Marfans
2-3/10k.
Describe the amorphous ground substance of the ECM.
It is made up of
- Proteoglycans (chondriotin, heperan, and keratan sulfates)
- Hylauronan
- Glycoproteins (cytokines, growth factors and structural proteins)
- Extracellular proenzymes.
How do cells interact with the ECM?
The cell and ECM interact via
integrin receptors, syndecans, CD44, selectins, dystroglycans, growth factor receptors and cytokine receptors.
Describe embryonic connective tissue?
Embryonic connectibve tissue is RICH in ECM and mesenchymal stem cells.
It has some, but not many collagen or reticular fibers.
In the umbilical cord, embryonic connective tissue can be referred to as what?
Warton’s Jelly. It is firm because it is rich in ECM.
What are [adult mesenchymal stem cells]?
Multipotent stem cells that can be made into fibroblasts, muscle cells (skeletal and smooth), osteoblasts, chondrablasts and adipocytes.
Thus, adult mesenchymal stem cells are more restrictive than embryo.
What is a macrophage?
Macrophages are made from blood monocytes.
Their job is to perform phagocytosis and destruct bacteria, sick cells, remove debris and process and present antigens.
Mast cells
Secrete histamine (mediates allergic responses) and heparin (anti-coagulant)
Plasma Cells
Made from B-lymphocytes.
Their job is to make antibodies.
In the bone, is the ECM gel-like?
No, the bone is mineralized.
What is elastin made up of?
Tropoelastin
Fibulin 1
Fibrillin 1
Fibrillin 2
What is hylauronic acid?
Hylauronan link proteoglycans together.
A high amount of these proteoglycanic aggregates can be found in cartilage.
What are the three types of loose connective tissue?
- Areolar connective tissue
- Adipose connective tissue
- Reticular connective tissue
Loose areolar connective tissue
A type of loose connective tissue that is low-density and has both fixed and wandering cells.
Types of fixed cells
Fixed cells are primarily responsible for depositing the ECM.
- Fibroblasts
- Adipocytes
- Mesenchymal cells
Types of wandering cells
Wandering cells come from circulation.
- Macrophages
- Mast cells
- Leukocytes/lymphocytes
- Plasma cells
What is loose connective tissue and where is it found?
LCT is low in fibrous type collagen and elastin.
It [supports and binds other tissue], [holds body fluids] and [defends against infection].
It is found immediately below the epithelia (called lamina propia), around BV, muscles and nerves
Adipose connective tissue
- Loose connective tissue that has a bunch of adipocytes and little ECM in between the cells.
- Role: stores NRG and insulates, supports and protects our organs
Where is adipose connective tissue found?
Under the skin, around organs, in our abdomen, breasts and butt
What is white fat?
Stores NRG, insulates, cushions important organs, secretes hormones
What is brown fat?
Important in thermogenesis. Abundant in newborns but greatly reduced in adults
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What is reticular connective tissue and where is it located?
Loose connective tissue that is rich in reticular fibers. It create a supportive mesh to hold free cells, such as blood cells and immune cells outside of the blood and lymphatic vessels.
It is found in the [liver, bone marrow, lymph nodes, and spleen]
What is dense irregular connective tissue?
Has alot of fibrous ECM, with collagen fibers running in random patterns.
Fibroblasts are the main principle cell type.
What is the main principle cell type found in dense irregular connective tissue?
Fibroblasts
Where is dense irregular connective tissue found?
- Dermis layer of the skin
- Capsules that surround internal organs
- Perichondrium and periosteum
- Fascia
What is dense regular connective tissue?
Has a lot of fibrous ECM, with collagen fibers that are regularly arranged.
Because of this arrangement, it will resist pulling forces and is poorly vascularized.
When not under tension, it looks wavy
What is the main principle cell type found in dense rregular connective tissue?
Fibroblasts
When dense regular connective tissue is damaged, how long does it take to heal?
It takes a while to heal because of the regular arrangement.
When not under tension, what does dense regular connective tissue look like?
Wavy
Where is dense regular connective tissue found?
Ligaments, tendons, aponeuroses, dense fascia and joint capsules
What is [elastic connective tissue]?
Elastic connective tissue is dense connective tissue that is rich in elastin. This allows tissue to recoil after stretching.
Where is elastic connective tissue found?
- Blood vessels
- Bronchiole tubes
- Special ligaments, such as ligamentum nuchae.
What are fibroblasts?
Make collagen, elastin, reticular fibers, proteoglycans and glycoproteins in the ECM.
What do adipocytes look like under the microscope?
The nuclei of adipocytes are pushed to the side because the droplets have so much adipose.
What are adipocytes?
Adipocytes remove lipids from blood, store it and release it into the blood when needed. It stores NRG.
A high amount of proteglycan aggregates can be found where?
cartliage
Does embryonic connective tissue have a lot of collagen and reticular fibers?
Some, but not much.
Describe adults CT
Adult CT is fibrous. It can be loose, dense regular, dense irregular
