Cell and Molecular Biology Lecture 4: Histology of Connective TIssue

What is the name of the group of tissues which connect or bind other tissues of the body?

Connective tissues

What is the general/primary/overall function of connective tissues?

Help to maintain a functionally integrated body

What are the specific functions of connective tissue?

1. Support and connect other tissues

2. Protect and insulate inner organs

3. Connect and bind tissues (ligament and tendon)

4. Transport system (blood and lymph)

5. Store energy (adipose tissue) and calcium/phosphorous (bone)

6. Immune function (white blood cells and mast cells)

What are the three main components of connective tissues?

Cells, ground substance, fibrous proteins

True/False: The proportion of cells, fibers, and ground substance does not vary from one type of connective tissue to another

False

Bone is what type of connective tissue?

Solid

Synovial fluid is what type of connective tissue?

Semi-solid

Blood is what type of connective tissue?

Liquid

What is classification of connective tissue based on?

Matrices, cells, and fibers

What is the common origin of all conenctive tissues?

Mesoderm

What are the two different groups of cells classified as connective tissues and, generally, where are they derived from?

Fixed/resident (mesenchymal), free/wandering (hematopoietic)

What are examples of fixed or resident cells?

Fibroblasts, myofibroblasts, pericytes, fat cells, macrophages in the liver (Kupffer cells)

What are examples of free or wandering cells?

Plasma cells, mast cells, leucocytes or white blood cells, macrophages

What are the types of white blood cells?

Lymphocytes, basophils, neutrophils, basophils, monocytes, and eosinophils

What is the exception to the generalization about where the two different groups of connective tissue cells are derived from?

Macrophages in the liver are derived from hematopoietic stem cells

What are the majority of the cells in connective tissue classified as?

Fibroblasts

What is the shape of the nucleus in fibroblasts?

Giant, elliptical, oblong

How many nuclei do fibroblasts have?

One or more

What are some of the features of the organelles in fibroblasts?

Many mitochondria, rough endoplasmic reticulum, Golgi complex

What do fibroblasts do?

Secrete the fibers and ground substance of the extracellular matrix

What characterictics do myofibroblasts have?

Characteristics of both fibroblasts and smooth muscle cells

What do myofibroblasts, similar to SMCs, have in them?

Actin, myosin, desmin

What are myofibroblasts used for?

Tissue repair

Where are myofibroblasts found in the mouth?

Periodontal ligament

Where are pericytes found in the body?

Around capillaries and venules

What other connective tissue cells do pericytes have the same characteristics as?

Myofibroblasts

What do pericytes have that myofibroblasts don't have?

Tropomyosin

What are pericytes involved in around the body?

Wound healing

What do pericytes differentiate into during blood vessel formation and repair?

Fibroblasts, smooth muscle cells, and endothelial cells of blood vessel walls

What differentiates into lipoblasts?

Undifferentiated mesenchymal cells

What do lipoblasts differentiate into?

Adipocytes

What are the two different types of fat cells?

Multilocular, unilocular

What type of cells are white adipose tissue?

Unilocular fat cells

What are the hallmarks of unilocular adipose tissue cells?

Fat droplet, displaced nucleus, cytoplasm, golgi to the periphery, sparse rough ER, small Golgi complex

What type of cells are brown adipose tissue?

Multilocular fat cells

What is the size of multilocular fat cells compared to unilocular?

Smaller

What is the main difference between brown and white adipose tissue?

Brown contain small and several fat droplets while white is a singular large fat droplet

What are the hallmarks of multilocular fat cells?

Eccentric nucleus, no rough ER (but do have smooth ER), many mitochondria, few free ribosomes

What are plasma cells derived from?

B-lymphocytes

Where is the nuclei located within plasma cells and what does it look like?

Eccentrically; clock-face-like chromatin

Where are plasma cells located?

Throughout the connective tissues in areas of chronic inflammation and infection

What is the primary function of plasma cells?

Produce antibodies to destroy pathogens

Where are antibodies stored in plasma cells?

Dilated cisternae

What do mast cells have in the cytoplasm?

Granules

What is the main function of mast cells?

Storage of chemical mediators in granules

What does heparin do?

Inhibit clotting

What does histamine do?

Dilate blood vessels

What does the release of heparin and histamine (chemical mediators) do?

Facilitate innate immunity, inflammatory responses, and tissue repairs

What are the two major categories of leukocytes (white blood cells) in mammals?

Polymorphonuclear granulocytes and mononuclear agranulocytes

What are the three polymorphonuclear granulocytes?

Neutrophils, eosinophils, basophils

What are the two mononuclear agranulocytes?

Monocytes, lymphocytes (T-cells and B-cells)

What are the functions of leukocytes?

Defend against infection and inflammatory processes

How do leukocytes function?

Phagocytosis

Where are leukoctes present?

Sites of chronic inflammation

Where are macrophages found?

Spleen, lymph nodes, thymus, bone marrow

Where are Kupffer cells found? (A type of macrophage)

Liver

Where are dust cells found? (A type of macrophage)

Lungs

Where are Langerhans cells found? (A type of macrophage)

Skin

Where are monocytes found? (A type of macrophage)

Blood

What is the primary function of macrophages?

Phagocytose damaged/dead cells, foreign substances, and pathogens

What are the types of embryonic connective tissue?

Mesenchymal and mucosal

What is the only site at which mesenchymal connective tissue is present?

Embryo

What type of nucleus does mesenchymal connective tissue have?

Oval

What is the function of mesenchymal connective tissue?

Differentiate into the majority of connective tissues

What does Wharton's jelly consist of?

Ground substance mainly of hyaluronic acid, sparsely populated type I and III collagen

What type of umbilical mucoid cells appear in Wharton's jelly?

Spindle shaped

Where is Wharton's jelly found?

Umbilical cord

What is the function of Wharton's jelly?

Protects the umbilical cord vessels. Postnatal source of fetal stem cells.

What are the types of connective tissue proper?

Dense, loose (areolar), reticular, adipose

What are the two types of dense connective tissue?

Irregular and regular

Why is dense irregular connective tissue called as such?

The arrangement of collagen with fibroblasts is irregular

What is the direction of tension that irregular dense connective tissue can withstand?

Many directions

Where is dense irregular connective tissue found?

Perichondrium of cartilage tissue, dermis of the skin, fibrous coverings that surround some organs, capsules of fibrous joints

Why is dense regular connective tissue called as such?

Type I collagen fibers arranged in parallel bundles

What is the principle cell type of dense regular connective tissue?

Fibroblasts

What is the direction of tension that regular dense connective tissue can withstand?

Tensile (pulled or stretched)

Where is dense regular connective tissue found?

Tendons (attach muscles to bone); ligaments (bind bones together at joints)

What does areola mean?

Tissue with small spaces

What does the extracellular matrix of loose or areolar connective tissue contain mostly?

Loosely woven mix of fibers with semi-fluid ground substance

What type of cells are found in loose or areolar connective tissue?

Fixed + wandering macrophages, fibroblasts, mast cells, plasma cells, fat cells, lymphocytes

Where is loose or areolar connective tissue found?

Areas where the body attacks the inflammation; subcutaneous layer

What does reticular fiber consist of?

Type III collagen

Where is reticular tissue found?

Liver, spleen, lymph nodes, adipose tissue, bone marrow

What does reticular tissue do?

Provide structural supprot to organs; hold adipose tissue together

Is white adipose tissue more common in adults or children?

Adults

Is brown adipose tissue more common in adults or children?

Children

What gives brown adipose tissue its color?

Iron

What is hay fever?

Seasonal allergy causing mucous membrane inflammation of the nose and eyes via mast cell histamine release

What is the treatment for hay fever?

Anti-histamines block the histamine receptors on cell membranes and prevent them from acting

What is hypertrophic obesity?

Increase in the size of unilocular fat cells due to accumulation and storage of fat

What is hypercellular obesity?

Over-abundancve of total number of adipocytes

What are lipomas?

Benign tumors of adipocytes

What are liposarcomas?

Malignant tumors of adipocytes

Where are liposarcomas most developed?

Leg and retroperitoneal tissues