Tissues Flashcards
What are the four types of tissues in the human body?
Epithelial, Connective, Muscle, Nervous
What are 3 places that epithelial tissue is found?
- Covering body surfaces
- Lining body cavities
- Forming glands
Epithelial cells rest on a….
basement membrane /basal lamina
What are the 3 major functions of epithelial cells
- Covering and lining (protection)
- absorption
- Secretion
How do epithelial cells receive their nutrition?
All epithelial are avascular (no capillaries).
They are dependent on proximity to loose connective tissue for their nutrient and oxygen supplies and by-product removal
What always lies on the interface between epithelial cells and connective tissue?
a basal lamina
What are 3 chief characteristics of epithelial cells ?
- Form a sheet of closely associated cells held together by junctional complexes with very little intercellular space
- Ability to shed and renew
- Made up by polarized epithelial cells that have specific functions depending on the location in the body
What are the 8 types of epithelial tissue?
- Simple squamous
- Stratified squamous
- Simple cuboidal
- Stratified cuboidal
- Simple columnar
- Stratified columnar
- Pseudostratified columnar
- Transitional
What kind of places are simple squamous epithelia found in? what are some examples?
places where there is a very rapid passage
of chemicals
ex:
1. Endothelium of lymphatic vessels
2. Alveoli of lungs
3. Lining of capillaries
4. Some parts of kidney glomerulus and tubules
What functions can simple squamous epithelium perform?
some simple secretion (such as lubricating substances), and some filtering
Simple squamous epithelium lining blood vessels is called ?
endothelium
The simple squamous epithelium that covers body cavities is called?
mesothelium
What are 2 key differences between simple squamous epithelium and simple cuboidal epithelium?
- thicker (cube shaped) and more protective
- a more complex cytoplasm, and perform more complex functions in terms of secretion and absorption
- still allow passage of chemicals
What are two examples of where simple cuboidal epithelium is found?
The secretory part of most glands (like the thyroid for example)
Most tubules of the kidney
What is the morphology of simple columnar epithelium?
A single layer of tall cells. The nucleus tends to be elongated and localized near the basement membrane
Have microvilli and/or cilia
What tasks are simple columnar epithelium active in?
Secretion and absorption
Where are simple columnar epithelium found? (2 examples)
- Bronchioles (ciliated)
2. Small intestine (microvilli)
What is the distinguishing morphology of pseudostratified columnar epithelium? (2 things)
- Cells are tall and thin, but vary in height – all touch the basement membrane, but not all make it to the apical surface
- The nucleus may be found at different points/levels
Can pseudostratified columnar epithelium have cilia?
Yes
Where is an example of pseudostratified columnar epithelium?
Trachea
What types of cells tend to be intermixed with pseudostratified columnar epithelium?
Mucous secreting goblet cells
How is stratified epithelial tissue named?
based on the type of cell found at the surface
What is the most common type of stratified epithelium?
stratified squamous epithelium
- lower layers may be cuboidal or columnar
what is the main useful feature of stratified epithelium?
protection and durability
What are the two groups of stratified squamous epithelium (based on secretion)
Keratinized and non-keratinized
What makes stratified squamous epithelium keratinized? where is this type found? what does it constitute?
flattened superficial layer loses their nuclei and become filled with keratin (keratinized)
Found on the outside of the body
Constitutes the epidermis
What makes stratified squamous epithelium non-keratinized? where is this type found?
consists of several layers of cells with the most superficial layer composed of flat living cells
-mucosal type
Lines the moist body surfaces, such as mouth, esophagus, vagina
Where is stratified cuboidal epithelium found?
Lines the ducts of sweat glands but otherwise uncommon
- also salivary and mammary..?
Where is stratified columnar epithelium found? is it common or uncommon?
Uncommon but occasionally found in large excretory ducts of some glands and in the cavernous urethra
What is transitional epithelium?
a stratified epithelium which undergoes marked changes in appearance, depending on the degree of stretch
Where is transitional epithelium found?
Lines excretory passages in the urinary system (i.e., the urothelium)
What is the main location and function of simple squamous epithelium?
location: air sacs of the lungs and lining of blood and lymphatic vessels
function: allowing materials to pass by filtration and diffusion. Also secreting lubricating substances
What is the main location and function of simple cuboidal epithelium?
location: in ducts and secretory portions of of small glads and kidney tubules
function: secretion and absorption
What is the main location and function of simple columnar epithelium?
location:
- cillated tissues in the bronchi, uterine tubes, uterus,
- smooth tissues: in the digestive tract and bladder
function: absorption as well as secreting mucous and enzymes
What is the main location and function of pseudostratified epithelium?
location: cilliated tissue lines the trachea and upper respiratory tract
function: secretes and moves mucous
What is the main location and function of stratified squamous epithelium?
location:
- keratinized: constitutes the epidermis
- non-keratinized: lining the esophagus, mouth and vagina
function: protect against abrasion
What is the main location and function of stratified cuboidal epithelium?
location: sweat, salivary, and mammary glands
function: protective tissue
What is the main location and function of stratified columnar epithelium?
location: uncommon but found in some ducts and urethra
function: secretes and protects
What is the main location and function of transitional epithelium?
location: lines the bladder, urethra, and ureters
function: allows urinary organs to expand and stretch
What are 4 specializations of the lateral surface of epithelial cells?
all are junctions
- Occluding (zonula occludens or tight junctions)
- Adhering (zonula adherens)
- Desmosomes (macula adherens)
- Communicating (gap junctions)
What is the function of hemidesmosomes? where are they found?
Found on the basal surface
Attachment to the basal lamina
What are two specializations of the apical surface of epithelial cells?
cilia and microvilli
What are tight junctions? What do they do? what is attached to what?
Appear as “fusions” of the cell membranes to one another
- form a barrier
formed by proteins, like occulin, claudin. Attached to actin
What are adhering junctions? what do they do? what are they made of? what attaches to what?
Sticking adjacent cells together.
Made of proteins such as cadherin. Attached to actin filaments all around the cell.
What are desmosomes? what do they do? what are they made of? what attaches to what?
These are points of attachments.
The cells can have a bit of space between spanned by cadherin and intermediate filaments (cytokeratin in epithelia).
What are gap junctions for? What are they made of?
for cell to cell communication
Pores formed by arrangement of connexin proteins that permit passage of ions and other molecules.
What do tight/occluding junctions greatly reduce the passage of?
water electrolytes and other small molecules
What are the main cell joining proteins in tight/occluding junctions?
Occludin and claudin
- anchored within cell to actin
What is the order of junctions?
- tight/occluding junctions are the most outer ones
- zona adherens is below
- macula adherens/desmosome
- gap junctions
What does the zona adherens do?
Attaches epithelial cells together
How does the zona adherens attach epithelial cells together? what proteins are involved?
Transmembrane cadherins on each cell interact with one another to form a link
Actin on the inside of the cell interact with the junction and form a “belt” all the way around the inside of the cell
How do desmosomes connect? how is it different from the zona adherens?
Cell-cell connection through cadherins
Anchored to intracellular filaments – in epithelia, this is cytokeratin (instead of actin)
What is different with desmosomes compared to other junctions?
there can be more space between cells that with other types of junctions
What is a connexon ? what is it formed by?
A pore formed for gap junctions
formed by 6 connexin proteins
What can pass through connexons?
small water soluble molecules
- not nucleic acids or proteins
What proteins are involved in the hemidesmosome connection between the epithelial cell and the basement membrane?
Keratin filaments anchor the hemidesmosome to the inside of the cell
connected by integrin
anchored to the basement membrane by laminin
Define: gland
one or more cells that make and secrete a fluid or chemical message
What are 3 factors used to classify glands
The development of the gland (exocrine or endocrine)
The shape of the gland
The mechanism of excretion
Define: exocrine
Retain a passage and secrete onto the surface of the epithelium
- ex: salivary glands
Define: endocrine
Lost contact with epithelium – secrete into vessels
- ex: thyroid
What do exocrine glands have that allows them to secrete to the outside?
ducts (involutions of epithelium)
What are 4 examples of exocrine glands
sweat, salivary, sebaceous, mammary
What are the 3 types of secretion products that can come from an exocrine gland? what are they rich in?
Mucus – rich in glycoproteins
Serous – rich in proteins and watery
Sebaceous – rich in lipids
Endocrine secretions are released into the?
blood
What are the 3 components of connective tissue? which type of connective tissue lacks one of them?
- cells
- ground substance
- fibres
- blood lacks fibres
what type of cells does connective tissue come from
mesenchymal stem cells
what is the most common cell type in connective tissue?
fibroblast
in addition to fibroblasts, what are 5 other common cell types in connective tissue?
macrophages, mast cells, adipose cells, leukocytes, plasma cells
what do fibroblasts synthesize?
collage, elastin, proteoglycans and glycoproteins
what is the structure of the ground substance of connective tissue? what are the base components?
made of large molecules called glycosoaminoglycans(GAGs) which link together to form even larger molecules calledproteoglycans
What feature of ground substance is due to proteoglycans ? what is the benefit of this?
they are very good at absorbing moisture, making it so 90% of the extracellular matrix is water
this makes it so that the ECM is very good at resisting compressional forces
what is the structure of a glycosaminoglycan (GAG)
linear polysaccharides consisting of repeating disulphide units
- hydrophilic (charged and attract/retain water)
- inflexible
what is the structure of a proteoglycan?
a protein core with branched GAGs
What influences what can pass through the matrix?
the shape and property of the proteoglycans?
what are the three types of fibres prevalent in the extracellular matrix of connective tissues?
- collagen
- elastin
- reticular
what is the most abundant protein in the extracellular matrix/body? what %
Collagen
- 30% of the protein in the body
what is the morphology of the collagen fibres?
wide and wavy in appearance and generally stain pink
What is the structure/staining/composition of elastic fibres?
- made from elastin
- thin and flexible
- generally stain black
what are reticular fibres? what do they look like?
Are actually thin collagen fibres
appear thin and spider web like
stain black
how many types of collagen are there?
over 25
What kind of strength does collagen provide? what structural configuration gives this?
tensile
multiple polypeptide chains coming together to form a collagen molecule which then forms a microfibril, then fibril, then collagenous fibre
What type of collagen are reticular fibres made of? with what else?
type III collagen
- in association with other types of collagen, glycoprotein, and proteoglycans
what produces collagen? what produces reticular fibres? how are they similar or different?
collagen is produced by fibroblasts, reticular fibres are made from reticular cells (a type of fibroblast)
what produces elastic fibres?
fibroblasts and smooth muscle cells of arteries
What are the 2 main functions of connective tissue in the body?
- provision and maintenance of form
2. connecting and binding organs and cells to give support
tendons attach …. while ligaments connect…?
tendons: muscle to bone
ligaments: muscle to muscle
what is stroma?
Connective tissue within organs
What are 4 additional functions of connective tissue ?
- storage of fat
- defense and protection of the body against infection
- reduces friction
- repair after injury
What are the three classifications of connective tissue?
- Proper
- Special
- Supporting
What are the two categories of Proper connective tissue?
Loose and Dense
What are the two types of loose (proper) connective tissue?
Areolar and Reticular
What is Aerolar connective tissue? where is it found
very loose, slippery and supportive outer coat of organs
- attaches epithelial tissue to other underlying tissue
- surrounding tissue of organs
What is Reticular connective tissue? Where is it found?
web like “internal skeleton” for some organs. Example: spleen, Lymph nodes
What are the two types of dense (proper) connective tissue?
regular and irregular
What are two examples of regular dense (proper) connective tissue?
tendons and ligaments
what is an example of irregular dense (proper) connective tissue?
dermis (layer below the skin)
loose connective tissue has many ___ and more ___ but few__ compared to dense CT
many cells and more matrix but few fibres
How are the collagen fibres arranged/packed in regular dense CT? What does this allow them to do?
tightly packed and arranged in parallel
- very little ground substance between them
powerfully resistant to tension forces in one direction, but allow some stretch
What tends to be found between groups of fibres in dense regular CT?
attenuated fibroblasts
what is the fibrous morphology of irregular dense CT?
dense woven network of collagenous (and some elastic) fibres in a viscous matrix
abundant collagen fibres are arranged in bundles without a definite orientation
- gives tensile strength
What kind of strength/resistance does irregular dense CT have? where is it found?
Impact resistant and has strength in all directions
Found in the joints and forming the dermis of the skin
What types of cells are found in irregular dense CT?
fibroblasts (mostly inactive), mast cells, macrophages, and pericytes
What are pericytes?
contractile cells that wrap around the endothelial cells of capillaries and venules throughout the body
What are the two types of special connective tissue?
adipose and blood
What are 3 functions of adipose tissue?
Store energy, protect, insulate
which type of adipose cells are responsible for the synthesis and storage of fat ?
white adipose cells
- long term energy reserves
what is the main molecule of storage in white adipose tissue?
Largely made up of triglycerides
– high in energy
What is a less efficient energy source stored in the liver and muscle?
glycogen
Define: unilocular cells
cytoplasm and nucleus squeezed to a thin rim around the periphery of the cell
- cells don’t divide
- form (white) adipose tissue when present in large numbers
Brown adipose tissue is made of ____ cells. What does this mean?
Multilocular: contain many small fat droplets
What is the main role of brown fat?
to provide body heat (thermoregulation)
What are the two types of supporting connective tissue?
Cartilage and Bone
What are the 4 types of cells found in blood?
- RBC
- Leukocytes
- Platelets
- NK cells
What are the 6 types of leukocytes and their functions?
Neutrophil - chemical mediator Eosinophil - chemical mediator Basophil - chemical mediator Monocyte - lysosomal enzymes B-cell - immunoglobulins T-cell - interleukins
What is the ground substance for blood?
Plasma
What are the 3 types of cartilage?
- Hyaline
- Fibrocartilage
- Elastic
Which type of cartilage is the most common? what is the composition?
Hyaline
Few fibres which makes it not as strong as fibrous cartilage
Where is hyaline cartilage found?
joints and respiratory passages (nose, trachea)
Where is fibrocartilage found?
vertebral disks and the knew
What is fibrocartilage associated with? what is the composition What does this confer?
is associated with dense connective tissue,
Contains collagen fibres making it resilient (strongest of the cartilages)
What is elastic cartilage and where is it found?
Most flexible form
- matrix contains elastic fibres
found in the ear
What is the only type of cell found in healthy cartilage?
Chondrocytes
What do chondrocytes do?
They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans.
What is the key difference between the 3 types of cartilage?
The number of cells present
- Fibrous has the least, making it the most inflexible because of the increased amount of extracellular matrix whereas elastic has the most
cartilage is both ___ and ___
Avascular and aneural
What is the function of bone?
provides stability to the body, allows for movement with attachment of muscles, and storage of essential minerals
What are the 2 types of bone?
Compact (cortical) and spongy (trebeculae)
What are the differences between compact and spongy bone? why is this important functionally?
Compact: due to the strength, its main functions is to support the entire body.
Spongy: porous nature has a greater surface area compared to compact bone. This allows bone marrow to develop in the region of spongy bone.
What part of the bone provides hardness and resistance?
the bone matrix
What is the composition of the bone matrix?
minerals (e.g. calcium and phosphorus) and organic material (collagen and ground substance, which contains proteoglycans and glycoproteins)
Bone cells
What % of the weight of bone is mineral?
60%
- mainly calcium and phosphate.
What is the most abundant protein in the bone ?
collagens
- makes up 90% of matrix protein
What are the 3 types of bone cells?
osteocytes, osteoblasts, osteoclasts
What is the role of osteoblasts? where are they located? What do they differentiate into?
Synthesize the organic components of the matrix (collagen, proteoglycan, and glycoproteins).
Located in the surface of bone tissue. Differentiate into osteocytes
What is the role of osteocytes? Where are they found? where do they come from?
Derived from osteoblasts
Are found in lacunae (cavities)
Are involved in the maintenance and mineralisation of bone.
What is the role of osteoclasts? What are they?
multinucleated cells involved in the reabsorption of bone tissue.
What is bone remodelling?
lifelong process where mature bone tissue is removed from skeleton and replaced by new bone.
Also repairs bone following injury
Also involved in maintaining calcium homeostasis
What cell types is found at the interface of osteoclasts and osteoblasts
macrophages
during the first year of life __% of the skeleton gets remodelled and replaced
almost 100
For adults, bone remodelling occurs at a rate of about __% each year
10
What is osteoporosis?
a disease where decreased bone strength increases the risk of abroken bones
What is the cause of osteoporosis?
imbalance between bone resorption and bone formation
What is the morphology of smooth muscle cells? Where are they found?
Found around blood vessels and intestine
Have a single central nuclei and are NOT striated
What is the morphology of skeletal muscle?
Long fused cells with multiple offset nuclei that have a striated appearance
What is the morphology of cardiac muscle? What is present that is not in other types of muscle cells?
Branched cells with single offset nuclei
Striated (actin and myosin arranged in sarcomeres)
Presence of intercalated disks
What are nerves made of?
Bundles of axons from neurons
What cells assist the propagation of the nerve impulse and provide nutrients to the neuron?
Neuroglia (glial cells)
Nerve tissueis the maintissue component of:
both the CNS and the PNS
