Epithelium and Connective Tissue, Muscle and Nervous Tissue Flashcards
Epithelium Functions
Protection, absorption, secretion
Epithelium basic characteristics
Polyhedral cells attached to thin ECM, line organs, form glands, avascular, undergo mitosis, generally show polarity (apical and basal pole)
Basement Membrane
Thin layer of extra cellular material between epithelium and connective tissue. Called basal lamina under electron microscopy
Simple Squamous
Also called thin or low, single cell layer, often has appearance of “fried egg”, usually lines capillaries and other tubes
Stratified Squamous
Multiple layers of rounded cells, skin, oral cavity, etc. can be keratinized or not
Simple cuboidal
Single layer of square cells, usually lines ducts and tubes
Stratified cuboidal
Multiple layers of square cells
Simple columnar
Single layer of rectangular cells, often have apical cilia, usually line digestive tract
Stratified columnar
Multiple layers of rectangular cells
Pseudostratified columnar
Rectangular cells of irregular shape, one layer, often ciliated, usually lines respiratory tract
Urothelium
Like stratified squamous with puffy appearance, binucleated, found only in urinary tract

Simple Squamous Epithelium

Stratified Keratinized Squamous

Simple Cuboidal

Simple Columnar

Pseudostratified Columnar

Urothelium
Desmosome
“Spot welds”, encircle epithelial cell, made of cadherens bound to keratin filaments
Tight Junction/Zona Occludens
Form seals between adjacent cells, often found near apical side of cell
Adherens Junction/Zona Adherens
Anchor cells to neighbors like a belt, made of cadherens bound to catenin bound to cytoskeleton
Gap Junctions
Allow exchange of nutrients and signal molecules, formed by connexons made of connexin proteins

Left: Desmosome, Middle: Zona Adherens, Right: Tight Junction
Progenitor Cells
Stem cells, divide to form new epithelial cells, Ex.) Crypt intestinal stem cells
Transient Amplifying Cells
Divided stem cells that differentiate into different epithelial cells
Metaplasia
Alteration of adult tissue that changes type or distribution
Dysplasia
Metaplasia associated with disease occurance, Ex.) Normal columnar epithelium in intestines changing to squamous dysplasia in intestinal cancer
Cancer Progression
Normal cells > Dysplasia > Carcinoma > Malignant Carcinoma
Malingancy = breaking through basal lamina
Carcinoma
Adenocarcinoma
Sarcoma
Cancer of epithelial cells
Cancer of glandular epithelia
Cancer of non-epithelial cells
Connective Tissue
Includes extracellular matrix, resident cells, protein fibers and ground substance
Resident Cells
Permanent: Fibroblasts, Adipocytes, Macrophages, Mast Cells
Transient: Plasma cells, lymphocytes, Neutrophils, eosinophils
Fibroblasts
Secrete fibers and ground substance, growth factors, have abundant RER and Golgi
Myofibroblasts - after damage, contract like smooth muscle to close wound
Adipocytes
Fat cells, store lipids and make hormone
Macrophages
Phagocytic cells, Antigen Presenting Cells
Mast Cells
Made in bone marrow, store histamine, heparin, etc. for inflammatory response
Plasma Cells
Produce Antibodies, have eccentric nucleus
Lymphocyte
T and B cells, darkly stained nucleus, immunity
Neutrophils and Eosinophils
Rarely seen in CT unless there’s inflammation

Fibroblast

Adipocyte

Macrophage

Mast Cell

Plasma Cells and Lymphocytes
Only way to tell difference is by looking at Nucleus

Neutrophils and Eosinophils
Only way to tell difference is by looking for stained granules in eosinophils
Collagen
Most abundant protein in body
Type 1 Collagen fibers - most numerous, form bundles to resist stretch, appear under microscope as rope-like fibers
Type 3 Reticular Fibers - no bundles, allow stretch
Elastic Fibers
Elastin core surrounded by fibrillin, appear under microscope as wire-like fibers. Mutation in fibrillin gene causes Marfan syndrome
Ground Substance
Viscous fluid between cells and fibers that contains glycoconjugates (glycosaminoglycans, proteoglycans and structural glycoproteins)
GAGs and Proteoglycans
Glycosaminoglycans (GAGs) form “bristles” and Proteoglycans form “stem” of bottlebrush like proteins, can be huge, resist compression and are highly hydrated
Glycoproteins
Structural and adhesive proteins that attach cells to ECM via integrin receptors, Ex.) fibronectin and lamanin

Collagen Type I - reddish “ropes”
Elastic Fibers - bluish “wires”
Loose Connective Tissue
Most abundant type of connective tissue. More cells and ground substance, fewer fibers, immediately under epithelia
Ex.) Lamina propria - found under skin and gut tissue
Dense Irregular Connective Tissue
More fibers, few cells, little ground substance. Fibers arranged randomly. Deeper than loose CT, few nuclei
Dense Regular Connective Tissue
Fibers arranged in same direction, found only in tendons and ligaments

Loose and Dense Irregular Connective Tissue

Dense Regular Connective Tissue
Wound Healing
Inflammation > Proliferation > Maturation
Inflammation: Neutrophils and mast cells appear
Proliferation: Myofibroblasts appear, stem cells provide new epithelium
Maturation: Tissue restored. If injury was deep, scar may form
Fibrosis
Tissue scar from persistent tissue damage/inflammation
Parenchyma
Essential/functional elements of the organ
Ex.) Epithelial tissue of Kidney
Stroma
All other tissues of an organ, connective tissue, blood vessels, nerves.
Ex.) blood vessels, nerves and CT of kidney
Skeletal Muscle
Long, striated, multi-nucleated muscle fibers for strong, quick, discontinuous voluntary contraction. Nuclei peripheral
Cardiac Muscle
Short, branched, striated, single or binucleated fibers connected by intercalated disks (desmosomes, fascia adherens, gap junctions). Provide strong, quick continuous involuntary contraction
Smooth Muscle
Non-striated irregularly shaped fibers for weak, slow, involuntary contraction. Often have serpentine nuclei. Actin and myosin arranged in dense bodies and irregularly around cell

Skeletal Muscle

Cardiac Muscle

Smooth Muscle
Muscle Contraction in Skeletal and Cardiac Muscle
Troponin C binds to Ca2+ allowing Myosin heads to attach to Actin filaments. Release of ADP triggers power stroke, addition of ATP detaches myosin from actin, ATP hydrolysis “cocks” myosin head.
Smooth Muscle Contraction
Calmodulin binds to Ca2+ to allow myosin to attach to actin. The rest proceeds same as skeletal and cardiac

Sarcomere
Know I band, A band, M line, H zone, Z disk, sarcomere
Z disk made of alpha-actinin
Adjacent myofibrils held in register by vimentin and desmin
Mesenchyme
Mesoderm > Mesenchyme > Myoblasts > Muscle cells
Epimysium
Thick layer of dense irregular connective tissue that encloses entire muscle
Perimysium
Thin layer of dense irregular connective tissue that encloses a fascicle
Endomysium
Layer of connective tissue that surrounds individual muscle fibers

Epimysium, Perimysium, Endomysium
Synapse Process
- AP reaches axon terminal
- Ca2+ channels open
- Ca2+ causes release of neurotransmitter vesicles
- Neurotransmitter crosses synapse
- Neurotransmitter binds to receptors
- Trigger signal in post-synaptic neuron
Neuron
Cell body/perikaryon/soma - large amount of rough ER(nissl substance) and golgi, don’t divide
Dendrites - branched, receive incoming signals, have dendritic spines associated with memory
Axons - long myelinated, transfer signals to subsequent neurons

Neuron
Astrocytes
“Star-shaped” glial cells in CNS
Contain Glial Fibrillary Acidic Protein (GFAP)
Contribute to blood-brain barrier
Cause Glial scars
Reuptake neurotransmitters
Microglia
Macrophages of CNS, survey environment and mediate immune response
Contain GFAP
Oligodendrocytes
Myelinate multiple CNS axons
Do not contain GFAP
Schwann Cells
Also called Sattelite Cells
Only in PNS
Myelenate 1 axon each
Act as phagocytes
Groups of Neurons and Axons
Neurons in CNS: Nuclei
Neurons in PNS: Ganglia
Axons in CNS: Tracts
Axons in PNS: Nerves
Layers of neurons in CNS: Cortex

Astrocytes

Schwann/Satellite Cells in a Ganglion
Epineurium
Dense connective tissue around entire nerve
Perineurium
Dense irregular connective tissue around each fascicle
Endoneurium
Dense irregular connective tissue around each axon

Epineurium
Perineurium
Endoneurium
Gray Matter
Neurons, dendrites and their synapses
Found on the outside of the brain and the inside of the spinal cord
Neuropil
Region densely filled with dendrites and axons making synaptic contacts
White Matter
Axons, no neuronal cell bodies
On inside of brain and outside of spinal cord

Spinal Cord
Gray matter on inside, White matter on outside
Ependymal Cells
Line ventricles and central canal, simple cuboidal/columnar layer that expresses GFAP, secrete cerebrospinal fluid (CSF)
Choroid Plexus
Folded lining of ventricles, produces bulk of CSF

Choroid Plexus lined with Ependymal cells
Blood-Brain Barrier
Formed by astrocytes and other epithelial cells surrounding capillaries in the brain
Pyramidal Neurons
In brain, large, triangular neurons
Purkinje Neurons
Located in the Cerebellum, have large dendritic arbors
Enteric Ganglion
Nerve ganglion located below the glandular layer of the gut

Pyramidal neurons

Purkinje Neuron
Muscle structure/layers
Myofibril < Myofiber (muscle cell) < Fascicle < Muscle