Tissue Basics: Structure and Histology Flashcards
Name the four main types of tissue and give examples of where in the body each is likely to be found
- Epithelial - lining the outside of the body, cavities, glands
- Connective - connected to the epithelial to form skin, bone, cartilage, blood
- Nervous - in the brain
- Muscle - heart muscle wall
Describe or identify the shared features of epithelial tissue, including glands, such as cellular polarity, intercell
junctions, and the basement membrane
Epithelial tissue:
Polarity = epithelial cells have two sides with different features:
1. Apical side - facing the outside, top surface, may have microvilli or cilia
2. Basolateral surface - inner surface attached to the basement membrane
Tight junctions - exist between epithelial cells, selectively permeable(?) only some allow for paracellular transport, while others only allow transcellular transport
Basement membrane - thin layer at the basolateral surface that connect the epithelial cells to the connective tissue
**Classify an example epithelial tissue based on key structural or physiological features
Epithelial tissue:
1) Layering:
- Simple (single layer)
- Stratified (multiple layers)
- Pseudo-Stratified (seeming to be multi-layered but is only one layer)
2) Shape:
- Squamous (flat, thin, fast absorption and diffusion)
- Cuboidal (cube-shaped, absorb nutrients, and produce secretions)
- Columnar (tall, narrow, absorb nutrients, produce secretions)
Explain the basic definition of connective tissue and classify whether a tissue is a connective tissue
Connective tissue = must contain the presence of extracellular proteins/fibres and cells in a matrix
(cells + extracellular matrix = ground substance + fibres + cells)
Function: provides structural framework for other tissues, connects body parts, binding, support, protection from invasive microorganisms, insulation, storage of energy, transportation, etc.
Compare and contrast the structure and general functions of loose and dense connective tissue proper
Loose connective tissue = fewer density of extracellular fibres, more cells, and more ground substance, airy/disperal of fibres
= consists many cells, mainly fibroblasts, supporting matrix for blood, lymph, etc.
Dense connective tissue = denser extracellular fibres, tightly packed and smooth
= consists fewer cells, mainly fibrocytes, produces tendons and ligaments via strong, rope-like structures
Describe the key features of tissue repair in proper connective tissue, and predict consequences for the organism if a component of the repair process is disrupted
What is an organ?
two or more types of tissues working together to perform specific functions
What is a tissue?
a group of similar cells and their products working together to perform specific functions
What are the four general types of tissues that all tissues in the body fall under?
- Epithelial
- Connective
- Nervous
- Muscle
What is epithelial tissue?
tissue that lines surfaces, passageways, chambers, and forms glands
- epithelia, glands (endocrine and exocrine)
- avascular: does not have a blood supply
- innervated: supplied with nerves
What is connective tissue?
defined by the presence of extracellular fibres/proteins and cells in a ground substance matrix
tissue that fills internal space/stiffens space, structural support, stores energy
What is nervous tissue?
conducts electrical impulses, sends and receives info in the form of electrochemical signals, carries information
What is muscle tissue?
contracts to produce movement and mechanical force
What do muscle and nervous tissue have in common?
contain highly specialized cells adapted for very specific physiological roles + use a lot of energy
What do epithelial and connective tissue have in common?
more diverse in their functions, specializations, and where they are found
Where can epithelial tissue be found?
covers surfaces of the body (outside, inside), cavities, passageways
What are the functions of epithelial tissue?
provide physical protection, control permeability, provide sensation, and produce specialized secretions
Describe the structure of epithelial tissue/epithelium/epithelial cells?
Epithelial Tissue is made of Epithelium, which is made of Epithelial Cells
Epithelial Cells (single or multi-layered)
- Epithelial cells are all POLAR - have different features on different sides
- Apical side - exposed to outside/inside, contains microvilli/cilia
- Basolateral side - inner surface, attached to the basement membrane
- Basement membrane - thin layer that connects epithelial cells to the connective tissue
All epithelial cells share basic features, including ____________________–they have an _______ and _______ surface
All epithelial cells share some basic features, including
POLARIZATION – they all have an APICAL surface and a
BASOLATERAL surface.
What are tight junctions? What are the two types?
Tight junctions are proteins between the epithelial cells that define how water (and solutes) can move between the lumen and ISF
There are two types of tight junctions: leaky and tight
What is the apical surface of an epithelial cell?
top surface - exposed to internal body space or external environment, in contact with lumen
What is the basolateral surface of an epithelial cell?
bottom surface, attached to the sides, and basement membrane, in contact with the interstitial fluid
Differentiate “leaky” tight junctions from “tight” tight junctions?
“Leaky” tight junctions - allow paracellular transport of water and solutes because there is some space between the epithelial cells
“Tight” tight junctions - do not allow paracellular transport, only transcellular transport is allowed because there are no gaps between the two neighbouring cells
What is paracellular transport? How is it different from transcellular transport?
Paracellular transport = between the cells
Transcellular transport = through the cell
How do you classify epithelium?
- Layering
- Shape
What are the three types of epithelium? (layering)
- Simple: single layer
- Stratified: multiple layers
- Pseudo-stratified: appears to be multi-layered, but is only single layer (mostly one layer of cells with different shapes and sizes)
What are the three shapes of epithelium?
- Squamous - wide but narrow (flat)
- Cuboidal - cube-shaped
- Columnar - taller
Where can ciliated epithelium be found?
contains cilia on the APICAL side, but NEVER on the basement side
What is the function of stratified epithelium?
Stratified epithelium has multiple layers -> for areas experiencing more physical stress (if it loses the top layer, there are many more after that)
Why is it called “pseudo-stratified” epithelium?
It appears to be stratified but it is only one single layer of cells with many different shapes and sizes
What is connective tissue?
tissue defined by the presence of extracellular proteins/fibres and cells in a ground substance matrix
What are the functions of connective tissues?
establish structure, transport materials, protect organs, surround/support other tissues, store energy, defend the body from invasive microorganisms
What are the three types of connective tissues?
- Connective tissue proper
- Fluid connective tissue
- Supporting connective tissue
What is connective tissue proper?
A type of connective tissue where the matrix is a normal interstitial fluid, has solid proteins, and is a slightly sticky gel
Connective tissue proper includes those
connective tissues with many types of
cells and extracellular fibers in a syrupy
ground substance.
- can be further divided into LOOSE or DENSE types based on their cells and extracellular fibres
ex) loose or dense, areolar tissue, adipose tissue, or reticular tissue
What is fluid connective tissue?
A type of connective tissue in which all proteins are dissolved and the consistency is like a liquid
Fluid connective tissues have
distinctive populations of cells
suspended in a watery matrix that
contains dissolved proteins.
ex) blood or lymph
What is supporting connective tissue?
A type of connective tissue in which the matrix is SOLID (densely packed fibres)
Supporting connective tissues differ
from connective tissue proper in having
a less diverse cell population and a
matrix containing much more densely
packed fibers. Supporting connective
tissues protect soft tissues and support
the weight of part or all of the body.
ex) bone and cartilage
There are ______ types of connective tissue proper divided into ________ and _______ types based on the cells and extracellular fibres
There are TWO types of connective tissue proper divided into LOOSE and DENSE types based on the cells and extracellular fibres
Describe dense connective tissue proper
Dense = denser extracellular fibres
= very high proportion of extracellular proteins to cells
= less diversity
= extracellular fibres make up most of the volume of dense connective tissue
ex) tendon
Describe loose connective tissue proper
Loose = low density extracellular fibres
= proportionally fewer extracellular fibers to volume
= more diversity
ex) areolar tissue
What are fixed cells?
Connective tissue cells that always remain in their tissue - won’t move in or out or very far within it
- involved primarily with local maintenance,
repair, and energy storage
What are fibroblasts?
A type of fixed cell
- secretes the proteins of the extracellular matrix (proteins that form the ground substance)
- create the extracellular fibres
- young versions of fibrocytes
- do almost all the work in connective tissues
- immature
What are fibrocytes?
A type of fixed cell
- matured fibroblast
- not particularly active
- MAINTAIN the proteins in the extracellular matrix (maintain extracellular fibres)
- does not secrete much proteins
What are wandering cells?
Cells that can move into or through the connective tissue depending on physiological demand
- primarily defend and repair
damaged tissues
What are mesenchymal cells?
Stem cells that can divide to replace damaged cells (fibroblasts)
- mobile stem cells that repair damaged tissues
What are elastin fibres?
A type of fibre found in the extracellular matrix of connective tissues:
- made of elastin
- stretch
- recoil to original length after stretching or distortion
- will bounce back
- slender, branched, very stretchy
What are collagen fibres?
A type of fibre found in the extracellular matrix of connective tissues:
- strongest, most abundant fibre
- pre-dominantly made of collagen
- tough and flexible
- strong but not stretchy
- high tensile strength
- thick, straight, or wavy and often form bundles
- resist stretching
What is tissue membrane?
A layer of epithelial tissue + underlying layer of connective tissue = COVER SURFACES OF THE BODY
A thin layer or sheet of cells that covers the outside of the body, the organs, internal passageways that lead to the exterior of the body, and the lining of the moveable joint cavities
There are four types: mucous, serous, cutaneous, synovial
What is plasma membrane?
Membrane that separates interstitial fluid and intracellular fluid (phospholipid bilayer)
What is basement membrane?
Membrane that lines the basal side of epithelial tissues - connects epithelial cells to the connective tissue
What are the three types of epithelial membranes?
Mucous - contains glands, line passageways and chambers
Serous - secretes fluids, line body cavities of the trunk
Cutaneous - make up the skin, covers the surface of the body
NOT EVERYTHING IN YOUR BODY IS A __________________________________
NOT EVERYTHING IN YOUR BODY IS A TISSUE MEMBRANE
What is fascia?
Fascia - layers of connective tissues that are NOT directly connected to epithelium (not a membrane)
- surrounds organs and provides physical support
- superficial fascia, deep fascia, and subserous fascia
What are three questions to ask when differentiating tissue types?
- How metabolically active is the tissue?
(Tissues such as nervous and muscle use up a lot of energy) - How is the tissue supplied with its nutrients/gets rid of its waste?
(Epithelial tissues lack blood vessels, so it obtains nutrients by absorption and diffusion) - CAN THE TISSUE BE REPAIRED OR REPLACED IF IT IS DAMAGED?
(Epithelial = rapid proliferation, aka cells divide faster to re-establish a new sheet
Connective = increased rates of matrix secretion, accelerated the secretion of extracellular fibres)
What are the two general sets of defense mechanisms that are activated when connective tissue is injured?
Clots and scars
What is a clot?
formed out of fluid connective tissues/blood tissues
- platelets, cells bounding together
What is a scar?
formed out of proper connective tissues
- dense web of collagen fibres is secreted at the injury site
**Explain the physiological
mechanisms that underly at least
one cardinal symptom of scurvy
(e.g. loss of teeth, spontaneous
bleeding/bruising, or old
wounds reopening).
Vitamin C deficiency
- Vitamin C is essential for synthesizing collagen
- Vitamin C deficiency would indicate that collagen cannot be synthesized
- Collagen is an important component in the structural role that connective tissue plays
- Wounds cannot be repaired because there is not enough collagen to hold the connective tissues together
- This could result in old wounds reopening or spontaneous bleeding because of the open wound
The APICAL side of epithelial cells is in contact with ____________________________
Lumen
The basolateral side of epithelial cells is in contact with ________________________________
Interstitial fluid (ISF)
All connective tissues share 3 common characteristics:
- specialized cells
- extracellular protein fibres
- a fluid known as ground substance
extracellular fibre + ground substance = matrix
The various types of connective tissue occur throughout the body but are ________ exposed to the outside environment. Many types of connective tissue are ___________________________ (that is, they have many _____________) and contain ________________ that detect pain, pressure, temperature, and other stimuli.
- NEVER exposed to the outside environment
- Many types of connective tissue are HIGHLY VASCULAR
- That is, they have MANY BLOOD VESSELS
- Contain SENSORY RECEPTORS that detect pain, pressure, temperature, and other stimuli
What is a membrane
Physical barrier
How is synovial membrane different from true epithelia?
Synovial - lines freely movable joint cavities, develops within connective tissue, no basement membrane is present, etc etc
