LECOM- Histology Exam 1

Microtubule structure

Starts with a gamma tubulin ring at the negative (-) end, adds alpha/beta tubulin to the positive (+) end through the use of GTP

Purpose of microtubules

1. vesicular transport

2. movement of flagellum/cilia

3. separation of chromosomes in cell division

2 types of motor proteins

Kinesins= move towards the positive end of microtubules

Dyeins= move towards the negative end of microtubules

Actin

spontaneously assembles without a basal body, requires energy, and is very flexible

Intermediate filaments

structural role, do not continuously reform, cell-cell and cell-matrix junctions

Classes of intermediate filaments

Cytoplasm:

keratins= all epithelial cells

vimentins= fibroblasts and neurons

neurofilaments= neurons

Nuclear:

lamins

Where is the nuclear lamina located?

inside surface of the nuclear envelope

Perinuclear space

located inbetween the two bilayer membranes of the nuclear envelope; is continuous with the endoplasmic reticulum

What does the nuclear lamina do?

acts as a scaffold for the chromosomes and nuclear pores

Diseases associated with defective nuclear lamina

Progeria (premature aging)

Muscular dystrophy

Telomerase

Adds nucleotides to the ends of the telomeres; contributes to malignancy

Barr body

When one of two X chromosomes is repressed and remains condensed

What does the nucleolus do?

rRNA synthesis

ribosome assembly

regulation of the cell cycle

Nucleostemin

protein that regulates the cell cycle and influences differentiation

static cell renewal

no longer dividing (neurons)

stable cell renewal

divide as needed (smooth muscle)

4 DNA damage checkpoint locations

1. beginning of G1

2. middle of S

3. beginning of G2

4. middle of G2

4 basic tissue types

epithelial, connective, muscle, nervous

What does H&E stand for?

hematolxylin & eosin

Structures that stain basophilic

heterochromatin and nucleoli

Structures that stain eosinphilic

extracellular fibers

Epithelium

avascular, almost always lines a surface or tube, skin

Where is epithelium NOT located?

articular cartilage, iris, teeth

How do you identify transitional epithelium?

"umbrella cells"

define transitional zone

region where there is a change in cell type; highly susceptible to cancer

microvilli

"brush border"; involved in absorption

stereocilia/stereovilli

long and immotile microvilli

Where are stereocilia located?

epididymis, ductus deferens, cochlear and vestibular hair cells

Where are cilia located?

trachea, bronchi, oviducts

Role of the lateral domain

1. occluding/tight junctions (linked to actin)

2. anchoring junctions

a. zonula adherens -> actin

b. macula adherens ->

intermediate filaments

3. Communicating/gap junctions

4. Lateral folds

Role of the basal domain

1. basement membrane

2. cell to ECM junctions

a. focal adhesions -> actin

b. hemidesmosome ->

intermediate filaments

3. Basal cell membrane infoldings

Types of exocrine secretory mechanisms

1. merocrine= secretions

2. apocrine= vesicles

3. holocrine= cell dies

Types of endocrine secretory mechanisms

*Into blood

1. cord and clump

2. follicle

2 types of cell signaling

1. paracrine

2. autocrine

What color do mucous secreting glands stain?

Stain pale

What color for serous secreting glands stain?

cytoplasm= eosinophilic

nucleus= basophilic

serous demilune

dark, semilunar shape that is a defect in mucous glands

what is the primary role of muscle tissue?

contraction

sarcoplasm

muscle cell cytoplasm

why does muscle tissue stain eosinophilic?

High volumes of protein

3 types of muscle

1. skeletal

2. cardiac

3. smooth

Skeletal muscle

multinucleated, peripheral nuclei, striated, voluntary

Cardiac muscle

single nucleus, central nucleus, striated, involuntary, intercalated discs

Smooth muscle

single nucleus, central nucleus, not striated, involuntary, long cells; form in sheets that may go in different directions

endomysium

CT that surrounds individual muscle fibers

perimysium

CT that surrounds a bundle of fibers to form a fascicle

epimysium

CT that surround the fascicles to form a muscle

small to large muscle components

sarcomere (myofilaments)

myofibril

muscle fiber

fascicle

skeletal muscle

2 contractile myofilaments

1. actin (thin filaments)

2. myosin (thick filaments)

Sarcomere bands

H band= only myosin

I band= only actin

A band= actin and myosin

Which sarcomere band remains the same length throughout contraction?

A band

dystrophin

anchors the sarcomere to the surrounding tissue

What ion is required for muscle contraction?

calcium

sarcoplasmic reticulum

stores calcium; arranged around myofibrils; forms terminal cisternae

T tubules

invagination of plasma membrane into the muscle fiber that transmits action potential

Skeletal muscle: t tubule/SR

Triad at AI line: SR, T, SR; 2 triads per sarcomere

motor unit

the number of muscle fibers that a single neuron will innervate

2 types of sensory innervation in muscle

1. muscle spindle

2. golgi tendon organ

extrafusal muscle fibers

voluntary contraction, generate force, alpha motor neurons

intrafusal muscle fibers

small and found within muscle spindles; proprioception

muscle spindle

encapsulated (CT) intrafusal fibers within extrafusal muscle fibers; detects changes in muscle stretch; NO contractile proteins; afferent AND efferent innervation

golgi tendon organ

encapsulated (CT) SENSORY receptor found between muscle and tendon; regulates the amount of force necessary for contraction

Fascia adherens of intercalated discs

anchors thin filaments and makes up the transverse component

Macula adherens of intercalated discs

desmosomes; hold cells together during contraction

Cardiac muscle: t tubule/SR

SR is NOT well organized

Only 1 t tubule per sarcomere

Diad: terminal cisternae (of SR) and T tubule at Z line

Purkinje fibers

Large and pale; generate heart beat without "guidance"

Smooth muscle: t tubule/SR

NON-EXISTENT

Calcium delivered via calveolae; regulated by the autonomic (involuntary) nervous system

Since smooth muscle does not have sarcomeres, how does it contract?

Dense bodies- anchor thin filaments (just like a Z line) and are situated close to the cell membrane in the sarcoplasm

What type of muscle actively divides through mitosis?

smooth muscle, in response to injury

morphology of connective tissue

large spaces filled with ECM; most are migrants from vascular system

location of connective tissue

usually found under epithelial cells

functions of connective tissue

space filling and support

fibers of extracellular matrix

collagen, reticular, & elastic

ground substance of ECM

glycoproteins, glycosaminoglycans, proteoglycans

*GAGs are attached to proteoglycans

what is a tropocollagen molecule?

3 glycoprotein alpha chains (left handed triple helix)

4 types of collagen fibers

Type 1- bone, skin, tendon/ligament

Type 2- hyaline cartilage

Type 3- reticular fibers

Type 4- basement membrane (below dermis)

Reticular fiber stains

eosin- red

PAS-red (stains glycoproteins)

Silver salts- black

role of reticular fibers

supprting structure for adipocytes, muscle cells, lymphatics, hemopoietic tissues

What produces reticular fibers?

mostly fibroblasts but also Schwann cells and smooth muscle cells

location of elastic fibers

elastic cartilage, arteries, and ligaments (lig flavum)

elastic fiber staining

eosin- red

orcein- brown

resorcin- bluish gray

two components of elastic fibers

elastin (central core) and fibrillin microfibrils around the core

What produces elastic fibers?

fibroblasts and smooth muscle cells

Marfan Syndrome

autosomal dominant mutation on c15; characteristic chest deformity and long arms

Ehlers-Danlos Syndrome

genetic collagen mutation; hyperflexibility of joints and skin

Osteogenesis imperfecta

genetic mutation in type 1 collagen assembly, "glass bone disease"

mesenchyme

embryonic CT; primitive pluripotent CT (capable of turning into other cell types); located around vessels in adults

mucus connective tissue

embryonic CT; present in umbilical cord, more space in between cells and less reticular fibers; gel-like ground substance

Wharton's jelly

jelly-like appearance of mucus connective tissue (embryonic)

dense regular connective tissue

few fibroblasts, large amount of collagen, parallel fiber arrangement

Where is dense regular connective tissue located?

tendons, ligaments, aponeuroses

Elastic connective tissue

When dense connective tissue contains large amounts of elastic fibers rather than collagen

dense irregular connective tissue

random fiber arrangement, contains fibroblasts

Where is dense irregular connective tissue located?

submucosa of hollow organs (underneath muscle layer)

Fibroblasts

star shaped cells with disc-like nucleus, contain rER, synthesize fibers

difference between fibroblasts and myofibroblasts

myofibroblasts contain contractile elements

loose connective tissue

loosely arranged fibers, found beneath the epithelium, contains blood cells, can swell

resident cell population of loose connective tissue

fibroblasts

myofibroblasts

adipose cells

macrophages

mast cells

mesenchymal cells

transient cell population of loose connective tissue

lymphocytes

plasma cells

basophils, eosinophils, neutrophils (granulocytes)

white adipose connective tissue

differentiate from mesenchymal cells; single lipid drop that fills cytoplasm, ring shaped cytoplasm and flat peripheral nucleus