Connective Tissue

Def of connective tissue

A diverse group of tissues that share a common origin, the mesenchyme (mesoderm) of the embryo

Characteristics of connective tissue

few cells not adherent to each other surrounded by an abundant matrix that bears mechanical stress. Vascular, and derived from the mesoderm

Conn tissue is predominantly composed of:

fibers, ground substance, cells (scarce)

Types of fibers in conn tissue

collagen, reticular, elastic

Most abundant structural fiber of connective tissue

collagen

Properties of collagen

acidophilic, unbranched, but flexible with indefinite length and variable width that provides tensile trength

Collagen is a _______

glycoprotein

Collagen stains ___ with eosin, ____ with Mallory, and ____ with massons

pink, blue, green

When stained with a heavy metal, what characteristics will collagen exhibit?

banding pattern, showing its arrangement into fibrils, tropocollagen

Most abundant collagen fiber type and where its found

I, bone, skin, tendon, ligamnts, cornea, internal organs

Location of type II collagen

cartilage, notochord, vitreous humor of the eye

Another name for type III collagen and where its found

reticular fibers, skin, blood vessels, internal organs, where its needs to be more flexible

Collagen that makes up the basal lamina

type I

How are reticular fibers unique from other collagens?

they can branch

collagen found in the reticular layer

type III

Reticular fibers found in the reticular organs are produced by ___

reticular cells

Reticualr fibers found between smooth muscle cells are produced by ____

smooth muscle cells

reticular fibers found surrounding acini of glands, adipocytes, small blood vessels, muscle and nerve are produced by ____

fibroblasts

Significance of reticular fibers in embryonic development and wound healing

reticular fibers are replaced by stronger type I fibers as embryonic development and wound healing progresses.

reticular cells are synthesized by what 4 cell types

fibroblasts, reticular cells, smooth muscle cells, Schwann cells

Describe the characteristics of reticular fibers

•thin fibers; 0.5 - 2 mm in diameter

•have striations when viewed with the EM

•coated with proteoglycans

Reticular fibers stain with ___ or ____

silver salts or PAS

reticular fibers are found in the ____ layer

reticular

what two cell types synthesize elastic fibers

fibroblasts and smooth muscle cells

Elastic fibers are selectively stained with ____ or ____

orcein; resorcon-fushin

Describe the structure of elastic fibers

smaller diameter than collagen with branches. intermixes with collagen to prevent tearing, forming loose 3-D networks, fenestrated sheets, or parallel bundles

Elastic fibers are composed of two structural components:

elastin and microfibrils

Describe microfibrils

- within and at the periphery of fiber

- electron dense when viewed with em

- contains the glycoprotein fibrillin

- fibrillin microfibrils organize the growing elastic fiber

How are scurvy and collagen related

results from vitamin C deficiency, vitamin C is required for the synthesis of the collagen molecule

- symptoms include fragile blood vessels, loose teeth/tooth loss, swollen and bleeding gums, sore/stiff joints, slow wound healing

How are Ehlers-Danlos syndrome and collagen related

- symptoms may include joint hypermobility, subluxations; soft-velvet-like skin; easily bruised; poor wound healing

- mutations in type III collagen (vascular type of Ehler Danlos Syndrome) may be the most severe because it affects blood vessels

Describe the elastic model

- each elastin molecule is randomly coiled due to its hydrophobicity

- elastin molecules are joined together by covalent bonds to form a network

-each elastin molecule can expand and retract

Marfans syndrome cause and characteristics

- mutations in the fibrillin gene

- characteristics: skeletal defects resulting in tall, lanky individual, long limbs and spider-like fingers, chest abnormalities, curvature of the spine, cardiovascular abnormalities that can result in dilation of the base of the aorta

Where are elastic fibers found?

In CT throughout the body but predominantly in organs than must stretch and then return to their original shape

Examples:

elastic arteries(i.e., aorta)

dermis of skin

lung

elastic ligaments

vocal folds

Describe the structure of ground substance

•High water content

•Contains proteoglycans

•Contains multiadhesive glycoproteins

what do proteoglycans to for ground substance

draws in water

Where is ground substance located

occupies the space between the cells and fibers

What is a proteoglycan

core proteins bound to glycosaminoglycan molecules

Functions of ground substance

(a)Mechanical support and withstanding compressive forces

(b)Rapid diffusion of water-soluble molecules

(c)Regulates activities of various growth factors & other secreted proteins

(d)Regulate molecular (and other types of) trafficking in the extracellular matrix

What is a glycosaminoglycan (GAG)?

- negatively charged, most abundant component of the ground substance

- responsible for the physical properties of ground substance

- form part of a proteoglycan molecule

What is hyaluronic acid and what is special about it?

a GAG, it is not bound to a protein, aka does not form a proteoglycan

functions of multi adhesive glycoproteins

stabilizes the extracellular matrix (ECM)

- links cells to components of the ECM

- regulates cell movement

- stimulates cells proliferation and differentiation

Fibronectin and laminin are ____

multi adhesive glycoproteins

Principle connective tissue cell

fibroblasts

Functions of fibroblasts

•Synthesize collagen, elastic and reticular fibers and components of the ground substances

•Contains rER and a prominent Golgi apparatus

•Under appropriate conditions can differentiate into other cell types, for example, myofibroblasts during wound healing

Another name for macrophages

tissue histiocytes

india ink or tryphan blue stains indicate what cell type

fibroblasts

Some functions of macrophages

phagocytosis, antigen presentation, secretion, tissue remodeling, inflammation, lymphocyte activation, microbicidal and tumorcidal activities

How to recognize a macrophage

indented, kidney-shaped nucleus

what system are monocytes part of

mononuclear phagocytic cystem

Macrophages are derived from what cell type?

blood monocytes

What happens when macrophages need to phagocytize a large foreign body?

the fuse to form a giant cell with many nuclei (100 is not unusual) aka foreign body giant cells

Describe the morphology of macrophages

•Abundant lysosomes and phagocytic vesicles

•Abundant rER, Golgi and secretory vesicles

•Can fuse with each other to form foreign body giant cells

•receptors present on the plasma membrane of Mast cells

IgE

Location of Mast cells

•Present in vicinity of small blood vessels

•Numerous in the connective tissue of skin and mucous membranes

Mast cells are absent from:

the CNS

Functions of Mast cells

hypersensitive reactions, anaphylaxis, allergies

Where do mast cells develop?

the bone marrow

Describe the morphology of Mast Cells

•Spherical nucleus

•Metachromatic granules containing histamine, SRS-A, ECF-A, and heparin

Contents of mast cell granules

histamine and SRS-A

heparin

eosinophil and neutrophil chemotaxic factors

leukotrienes

function of histamine and SRS-A

increase permeability of small blood vessels causing edema of surrounding tissue. skin rxn - itching

hepatin is a ____

anticoagulant

function of leukotrienes

trigger prolonged smooth muscle constriction in pulmonary airway resulting in bronchospasm

Morphology of a plasma cell

•Large ovoid cell (20 mm)

•Basophilic cytoplasm (ergastoplasm) and eccentrically placed nucleus

•Prominent nucleolus and peripherally placed clumps of heterochromatin

targets of chemical mediators

smooth muscle, mucous glands, small blood vessels, sensory nerve endings, eosinophils, blood platelets

Plasma cells are derived from ____

B-lymphocytes

T/F plasma cells produce antibodies

True

Location of plasma cells

GI and respiratory tract as well as salivary glands, lymph nodes and hemopoietic tissue

Morphology of reticular cells

•Stellate cells with pale staining nuclei and prominent nucleolus, can look like soccer balls

•Cytoplasm surrounds fibers

What are reticular fibers coated with and why

cytoplasm, to prevent an immune reaction to self

Location of reticular cells

in lymphatic organs, bone marrow and adipose tissue

Function of reticular cells

•Produce the reticular fibers in hemopoietic and lymphatic organs (except thymus)

•May be phagocytic in some organs

Function of adipocytes

•Secrete paracrine and endocrine substances

•Fat-storing cells (specialized for the synthesis & storage of lipid)

leptin

hormone made by adipose cells that decreases hunger and discourages eating in mice

Morphology of adipocytes

Lipid accumulation results in a 'signet-ring' appearance (flattened nucleus & cytoplasm surrounding large fat droplet)

Where do adipocytes tend to concentrate?

around small blood vessels

Connective tissue proper

loose, dense, regular, irregular

Connective tissue with special properties

adipose, elastic, reticular/hematopoietic, mucous

Supporting connective tissues

cartilage, bone

Location of connective tissue proper

•Found throughout the body

•Its boundaries are the epithelial basal lamina and the basal or external lamina of muscle, nerve, and the vascular endothelium

most widespread of CTs

loose connective

Location and function of loose connective tissue

•underlies the mesothelium lining the pleural and peritoneal cavity

•found where little resistance to stress is required

What happens in loose connective tissue

•site of immune reactions, gas and nutrient exchange

Structure of loose connective tissue

•more ground substance than cells

•tissue where blood vessels are distributed

Location and structure of dense irregular connective tissue

•Sparse cell population with little ground substance that consists mostly of fibers oriented in various directions organized into bundles

•Found in the dermis of skin, capsule of organs, sheaths of large neurons, dura mater of brain, and submucosa of hollow organs

Structure and location of dense regular CT

•Orderly arrangement of fibers as occurs in tendons, ligaments, and aponeurosis. also the cornea

Structure of reticular tissue

•Loose connective tissue where reticular fibers (Type III collagen) predominate

Location of reticular tissue

•Forms the stroma of bone marrow, spleen, and lymph nodes

•Prominent in embryonic tissue and in wound healing

Describe elastic tissue

•A form of dense connective tissue that is mostly elastic fibers, little ground substance and few cells

•Elastic fibers are interspersed with collagen fibers

Location of elastic tissue

ligamenta flava of the vertebral column, ligamentum nuchae of the neck, elastic ligaments of vocal folds of the larynx, and elastic arteries

yellow/pink stain in (hemolytic - something ?) is indicative of what type of tissue?

elastic

yellow-elastin

pink-collagen

Some locations of adipose tissue

hypodermis (panniculis adiposus)

omentum

mesentery

retroperitoneal space

breast

around kidney and eyeball

palms of hands and soles of feet

Which tissue type can also be considered an endocrine organ, secreting hormones

adipose

Two types of adipose tissue

white (unilocular) and brown (multilocular)

How to recognize white adipose tissue

•Closely packed white fat cells containing a single large lipid droplet (unilocular)

Location of white adipose tissue

•Found in subcutaneous tissue; its distribution is influenced by age and sex (also genes)

Morphology of brown adipose tissue

•Cells are smaller than that of white adipose tissue

•The cytoplasm contains multiple lipid droplets (multilocular)

•The nucleus is spherical and eccentric in position

Function of brown adipose tissue

•Brown fat is highly vascular

•Specialized for heat production

•Found in newborns and

species that hibernate

•Present in adult humans

locations of brown adipose in infants

between the shoulder blades, behind the breastbone and spine

Distribution of white adipose tissues decrease due to fasting in what anatomical areas?

omentum, mesenteries, retroperitoneal

Distribution of white adipose tissues do NOT decrease due to fasting in what areas?

orbit of the eye, major joints, palms and soles of feet