Histology lecture 1 & 2

8/10/26

Function of the nucleus

Store genetic material, controls cellular activity

function of the Plasma membrane

regulates what enters/exits cell, phospholipid bilayer, hydrophilic heads, hydrophobic tails

function of the Rough ER

synthesizes proteins that are exported out of the cell (sent to golgi) and contains attached ribosomes.

Function of the smooth ER

makes lipids, stores calcium and assists in detox

Function of mitochondria

energy production (ATP)

Golgi apparatus

packages and processes proteins for transport into vesicles

function of centrioles

paired microtubules inside the centrosome

FUNCTION of the centrosomes

organizes centrioles and mitotic spindle for division

Major components of the plasma membrane

phospholipid bilayer, cholesterol, transmembrane proteins, glycocalyx

Glycocalyx

make up of polysaccharides

help with cell signaling, adhesion and immune recognition

Types of nucleoprotein

Histone protein, non-histone protein

Histone protein

package DNA around histones (stuctural)

Non-histone proteins

enzymes that synthesize DNA and RNA, gene replication, regulate proteins

Heterochromatin

inactive/stored DNA, tightly coiled, looks dark and dense

Euchromatin

actively transcribing DNA, uncoiled, looks light

Major steps of protein synthesis

DNA→ mRNA→ proteins

transcription (nucleus) → translation (cytoplasm)

which organelle is responsible for mRNA translation to proteins

ribosomes

Free floating ribosome make

proteins that stay in the cell

rER ribosomes make

proteins for export and for plasma membrane

Exocytosis

when rER proteins are made and sent outside the cell

hormone secretion, digestion enzymes

Endocytosis

when vesicles bring proteins into the cell, 2 types

phagocytosis, receptor mediated

Phagocytosis

Cell eating, not picky

Receptor mediated

Cell eating after molecule binds to receptor

types of cellular transport

passive, facilitated, active, bulk transport

Passive diffusion

small, non polar molecules

facilitated diffusion

with concentration gradient, larger hydrophilic molecules, requires binding to carrier proteins to go through channels

Active transport

uses energy to cross membrane

Bulk transport

vacuoles containing large molecules M

Mitosis

cell division, results in 2 diploid daughter cells, identical

Meiosis

results in 4 haploid daughter gametes, sperm and eggs

components of cytockeleton

microfilaments, intermediate filaments, microtubules

Microfilaments

actin filaments for cell shape, movement and support

intermediate filaments

Purely structural and for support

Microtubules

active, form cilia and flagella, important for cell division, allow cell shape to change and be flexible

Chiasmata

chromosomal crossing over, only in meisosis

Cilia

hair-like projections that move things along the cell surface

cell types- ciliated epithelial cells

locations- respiratory system, uterus, ependymal cells lining brain ventricles

microvilli

finger like projections designed to increase surface area and absorb

cell types- absorptive epithelial cells

locations- small intestine, kidney tubules

goblet cell function

secrete mucus

Goblet cells

connective tissue components

cells and extracellular matrix

extracellular matrix

3 types of fibers, ground substance

3 types of extracellular fibers

collagen, elastin, reticular

Collagen

most abundant protein in the body

found in tendons, ligaments, skin and cartilage

gives tissue strength\

Elastin

found in skin, heart and lungs

allows tissue to stretch

ground substance

gel-like part of extracellular matrix that fills space

includes water, glycosaminoglycans, and hyaluronic acid (type of glycosaminoglycan)

basement membrane

thin supporting layer between epithelium and underlying connective tissue, act as a limiting membrane and are made of collagen 4

type 1 collagen

most abundant, provides strength

tendons, ligaments, bones, skin

type 3 collagen

forms reticular fibers to support cells and organs

type 4 collagen

forms basement membrane, supports cells and filters

type 6 collagen

anchors cells to extracellular matrix (velcro)

fibroblast

main connective tissue cell, make tropocollagen, repair tissues

fibroblast

Types of collagenous tissue

loose, dense irregular, dense regular, granulation

Loose collagenous tissue

found in areolar

Dense irregular collagenous tissue

found in dermis, sheaths of nerves, organ capsules

Dense regular collagenous tissue

found in ligaments and tendons

Granulation tissue collagenious tissue

wound healing and repair

Adipose tissue types

storage and fat processing, found in loose connective tissue, have receptors for growth hormones, insulin

White adipose, brown adipose

white adipose vs brown adipose

white adipose

energy storage

brown adipose

mostly in baby animals and hibernating animals, thermal insulation

cartilage structures

chondroblast

Chrondocytes

Perichondrium

Matrix

cartilage is avascular, so little blood supply

Hyaline cartilage

most common, in bone plates, joints, contains type 2 collagen

Hyaline cartilage (histology)

Elastic cartilage

contains elastin and elastic fibers, found in ear pinna, epiglottis and larynx

Elastic cartilage (histology)

Fibrocartilage

an intermediate between cartilage and dense connective tissue, tough, found in intervertebral discs

Fibrocartilage (histology)

Cartilage comoparison

Bone

composed of mineralized collagenous cells, type 1 collagen, hydroxyapatite

support system

bone cells

osteoblast, osetoclast, osteocyte

Osteoblast

bone formation, on the end of bone trabeculae

Osteocyte

resting stage of the osteoblast trapped in the matrix

Osteoclast

help in bone turnover, create channels in the bone, digest bone

Woven bone

immature bone, also seen in repairs, can become lamella, lots of collagen, unorganized

Lamellar bone

mature healthy bone, organized

2 types

Compact (cortical) bone

outter wall of bone

Cancellous (medullary) bone

interior, surrounds bone marrow

Woven vs lamenar bone (histology)

Endochondral ossification

Occurs in long bones, cartilage is growing from growthplate and replaced by bone

Intramembranous ossification

occurs in skull bones, grows from the mesenchymal tissue

dominant function of muscle tissue? and what causes it?

contraction and movement

caused by the interaction of actin and mycin

3 types of muscle tissue and where are they found

skeletal- voluntary muscles, make up the appendicular skeleton

smooth- involuntary/gastric muscles, also found in vessel walls

cardiac- found in the heart

skeletal muscle histology

striated, nucleus is off to the side, white endomysium

smooth muscle histology

long cell with tapered edge, central nucleus, no cross striations, has cartilage between cells

Cardiac muscle histology

striated, branching fibers that end in intercalating discs, central nucleus

what neurotransmitter is found in the neuromuscular junctions

acetylcholine

this also releases calcium ions

What is a motor unit

one motor neuron and all the muscle fibers it integrates

what is the organization of striated muscle

skeletal and cardiac have the same orginization

myofibers make up myofibrils which make up sarcomeres

what is a sarcomere

the contractile element of the myofiber

sarcomeres contract z-line to z-line

what happens when a myofiber depolarizes

it releases calcium ions from the sarcoplasmic reticulum, this shortens and contracts the muscle

what are the thick filaments of the sarcomere made up of

myosin

what are the thin filaments of the sarcomere made up of

actin

what is the function of smooth muscles in vessels and bronchioles

blood vessel- constricts, vasoconstriction

broncioles- bronchoconstriction

which layer of the blood vessel contains the smooth muscle

tunica media

what is the function of intercalating discs

transmits contractile forces between cells

contain gap junctions which allow rapid spread of excitatory stimuli with low electrical resistance.