Chapter 5 - Histology Flashcards
There are ____ trillion cells of ____ different cell types
There are 50 trillion cells of 200 different cell types
Name the 4 broad categories of tissues
Epithelial tissue
Connective tissue
Nervous tissue
Muscular tissue
Define histology
The study of tissues
Define organ
A structure with discrete boundaries that is composed of two or more tissue types
Define tissue
A group of similar cells and cell products working together to perform a specific role in an organ
The four primary tissues differ from each other in what three ways?
- Types and functions of their cells
- Characteristics of the matrix (extracellular material)
- Relative amount of space occupied by cells versus matrix
The extracellular matrix is composed of what two things?
1) Fibrous proteins
2) Ground substance (clear gel)
What other names can be used for ‘ground substance’?
Tissue fluid, extracellular fluid (ECF), or interstitial fluid
What are the six functions of epithelial tissue?
Covers body surfaces and lines body cavities
Protect deeper tissues from injury and infection
Produce and release chemical secretions
Excretion and absorption
Selectively filter substances
Makes up most glands
Describe the characteristics of epithelial tissue
Cells are very close together High rate of mitosis (regenerative) Apical and basal surfaces Basal surfaces faces basement membrane Apical surfaces may have microvilli or cilia Avascular but innervated
The ______ _______ anchors the epithelium to the connective tissue below it
basement membrane
Describe the differences between simple and stratified epithelium
Simple epithelia: -Contain one layer of cells -Named by shape of cells -All cells touch basement membrane Stratified epithelia: -Contain more than one layer -Named by shape of apical cells -Some cells rest on top of others and do not touch basement membrane
In _____ epithelia, not all cells touch the basement membrane
stratified
In ______ epithelia, all cells touch the basement membrane
simple
What are the four types of simple epithelia?
Simple squamous
Simple cuboidal
Simple columnar
Pseudostratified columnar
Describe pseudostratified columnar cells
Every cell reaches the basement membrane but not all cells reach the free surface; Falsely appears stratified
What are goblet cells?
Wineglass-shaped mucus-secreting cells in simple columnar and pseudostratified epithelia
Describe simple squamous epithelium and where it can be found
- Permits rapid diffusion or transport of substances
- Secretes serous fluid
- Locations: air sacs of lungs (alveoli), inner lining of blood vessels & heart (endothelium), and serosa
Describe simple cuboidal epithelium and where it can be found
- Absorption and secretion, mucus production and movement
- Locations: Kidney tubules and certain glands (thyroid, mammary and salivary glands)
Describe simple columnar epithelium and where it can be found
- Single row of tall, narrow cells; oval nuclei in basal half of cell
- Absorption and secretion; secretion of mucus
- Brush border of microvilli, ciliated in some organs, may possess goblet cells
- Locations: lining of GI tract, uterus, and uterine tubes
Describe pseudostratified epithelium and where it can be found
- Secretes and propels mucus
- Has cilia and goblet cells
- Looks multilayered, but all cells touch basement membrane
- Nuclei at several layers
- Locations: respiratory tract
Describe stratified epithelia
- Range from 2 to 20 or more layers of cells
- Some cells rest directly on others
- Only the deepest layer attaches to basement membrane
Describe the types of stratified epithelia
- Three stratified epithelia are named for the shapes of their apical surface cells
- Includes stratified squamous (only one expected to recognize and know functions)
- The fourth type is transitional epithelium
What is the most widespread epithelium in the human body?
Stratified squamous epithelium
Describe stratified squamous epithelia and its two types
-Deepest layers undergo continuous mitosis
-Daughter cells push toward the surface and become flatter as they migrate upward
-Top layer is exfoliated
-Two kinds
Keratinized—top layer is dead
Non-keratinized—top layer not dead
Describe keratinized stratified squamous epithelium and where it’s located
Resists abrasion; retards water loss through skin; resists penetration by pathogenic organisms
Locations: epidermis; palms and soles heavily keratinized
Describe non-keratinized stratified squamous epithelium and where it’s located
Resists abrasion and penetration of pathogens
Locations: tongue, oral mucosa, esophagus, and vagina
Describe transitional epithelium and where it’s located
Permits stretching (distension); surface cells change from round to flat when stretched Locations: ureter and urinary bladder
Describe the functions of connective tissue
Binding and Support Physical protection Immune protection Movement Storage Transport
_____ tissue is the most diverse and abundant type of tissue
Connective
Give examples of each of the functions of connective tissues
Connecting organs—tendons and ligaments
Support—bones and cartilage
Physical protection—cranium, ribs, sternum
Immune protection—white blood cells attack foreign invaders
Movement—bones provide lever system
Storage—fat, calcium, phosphorus
Heat production—metabolism of brown fat in infants
Transport—blood
Describe the characteristics of connective tissue
-Cells occupy less space than matrix (usually a large amount of extracellular matrix)
-Most cells are not in direct contact with each other
-Highly variable vascularity
Loose connective tissues have many blood vessels, whereas cartilage has few or no blood vessels
List and describe the 5 basic categories of connective tissue
- Fibrous Connective Tissue (Connective Tissue Proper): most diverse category; fibroblasts produce fibers and ground substance of matrix.
- Adipose Tissue: may be classified with loose connective tissue proper
- Cartilage (has 3 types): chondroblasts form matrix
- Bone (Osseous tissue): osteoblasts form matrix
- Blood
List and describe the three types of fibers that can be found in fibrous connective tissue
- Collagen fibers: tough, flexible, and stretch-resisant
- Reticular fibers: branching collagen fibers that forms a network
- Elastic fibers (Elastin): Allows stretch and recoil
What is fibrous connective tissue made of?
Fibers and a ground substance
Describe the ground substance of fibrous connective tissues
Usually has a gelatinous to rubbery consistency
Describe collagen fibers and where they’re found
Found in fibrous connective tissue, it is the most abundant protein: 25%. Tendons, ligaments, and deep layer of the skin are mostly collagen.
What is the most abundant proteines
Collagen (25%)
Describe reticular fibers and where they can be found
Found in fibrous connective tissue, it is thin collagen fibers coated with glycoprotein. Forms the framework of the spleen and lymph nodes.
Describe elastic fibers
Found in fibrous connective tissues, they branch and rejoin each other
What are the two main types of fibrous connective tissue? Describe them.
Loose connective tissue and dense connective tissue.
Loose connective tissue has more gel-like ground substance between cells, and its two types are areolar and reticular.
Dense connective tissue has fibers that fill spaces between cells, and its two types are dense regular and dense irregular.
What are the two main types of fibrous loose connective tissue?
Areolar and reticular
What are the two main types of fibrous dense connective tissue?
Dense regular and dense irregular
Describe areolar tissue (a type of fibrous loose connective tissue) and where it’s found
All 3 fibers are found; loosely organized; abundant blood vessels.
Wraps & cushions organs; underlies epithelia, in serous membranes, between muscles, passageways for nerves and blood vessels.
Areolar tissue—loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space
Possess all six cell types
Fibers run in random directions
Mostly collagenous, but elastic and reticular also present
Found in tissue sections from almost every part of the body
Surrounds blood vessels and nerves
Nearly every epithelium rests on a layer of areolar tissue
Blood vessels provide nutrition to epithelium and waste removal
Ready supply of infection-fighting leukocytes that move about freely in areolar tissue
Describe reticular tissue (a type of fibrous loose connective tissue) and where it’s found
Mesh of reticular fibers and fibroblasts
Forms supportive framework for lymphatic organs
Found in lymph nodes, spleen, thymus, and bone marrow
Describe dense regular connective tissue (a type of fibrous dense connective tissue) and where it’s found
Densely packed, parallel collagen fibers
Tendons attach muscles to bones and ligaments hold bones together
Describe dense irregular connective tissue (a type of fibrous dense connective tissue) and where it’s found
Dense, randomly arranged, collagen fibers
Withstands unpredictable stresses
Locations: dermis of skin; organ capsules
Describe adipose tissue
Space between adipocytes occupied by areolar tissue, reticular tissue, and blood capillaries
Functions: Energy storage, insulation, cushioning
Fat is the body’s primary energy reservoir
The quantity of stored triglyceride and the number of adipocytes are quite stable in a person
Fat is recycled continuously
New triglyceride synthesized while old molecules hydrolyzed and released to blood
Describe cartilage
Stiff connective tissue with flexible matrix
Describe what chondroblasts do
They produce the matrix that will trap them
Describe chondrocytes
Cartilage cells that are trapped in lacunae (cavities)
Describe perichondrium
A sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage (not articular cartilage); contains reserve population of chondroblasts
Describe the characteristics of cartilage
-No blood vessels, which means that diffusion brings nutrients and removes wastes and it heals slowly.
-Matrix contains collagen fibers
-Types of cartilage vary with fiber composition
(Hyaline cartilage, fibrocartilage, and elastic cartilage)
List the 3 types of cartilage
Hyaline cartilage, fibrocartilage, and elastic cartilage
Describe hyaline cartilage and where it’s found
Clear, glassy appearance because of fineness of collagen fibers
Locations: articular cartilage, costal cartilage, respiratory cartilage, fetal skeleton
Describe elastic cartilage and where it’s found
Contains abundant elastic fibers; covered with perichondrium
Provides flexible, elastic support
Locations: external ear and epiglottis
Describe fibrocartilage and where it’s found
Contains large bundles of collagen fibers
Resists compression and absorbs shock
Locations: pubic symphysis, menisci of knee, and intervertebral discs
Describe bone
Bone (osseous) tissue has a hard calcified matrix with collagen fibers
Define osteoblasts and osteocytes
Osteoblasts produce the matrix
Osteocytes are mature bone cells within lacunae
What are the two types of bone?
Spongy bone: porous appearance
Compact bone: denser, calcified tissue with no visible spaces
Describe compact bone
Compact bone is arranged in cylinders that surround central canals that run longitudinally through shafts of long bones
What type of tissue is blood, and what does it do?
Fluid connective tissue that transports cells and dissolved matter from place to place
Describe what blood is made of
Plasma (blood’s ground substance) and formed elements (cells and cell fragments)
List and describe the formed elements of blood
Erythrocytes—red blood cells (RBCs)
Leukocytes—white blood cells (WBCs)
Platelets—cell fragments involved in clotting
What are the two types of excitable tissues?
Muscle and nervous
Define excitability
The ability to respond to stimuli by changing membrane potential
Define membrane potential
An electrical charge difference (voltage) that occurs across the cell membrane
Describe what happens when changes in voltage happen in muscle and nerve cells
In nerve cells: changes in voltage result in rapid transmission of signals to other cells
In muscle cells: changes in voltage result in contraction, shortening of the cell
Define nervous tissue
A tissue specialized for communication by electrical and chemical signals
What are the two components of nervous tissue?
Neurons (nerve cells) and neuroglia (glial cells)
Describe neurons
Detect stimuli
Respond quickly
Transmit information rapidly to other cells
Cannot replicate/ divide
Describe neuroglia
Protect and assist neurons
“Housekeepers” of nervous system
More numerous than neurons
Can replicate/ divide
What are the three parts of a neuron?
Axon, dendrites, and neurosoma
Describe muscular tissue and its functions
- Elongated cells that are specialized to contract (shorten) in response to stimulation
- Primary job is to exert physical force on other tissues and organs
- Creates movements involved in body and limb movement, digestion, waste elimination, breathing, speech, and blood circulation
- Important source of body heat
List the 3 types of muscle
Skeletal, cardiac, and smooth
Describe skeletal muscle tissue
Long thin cells called muscle fibers; multinucleate
Most skeletal muscles attach to bone
Striations—alternating dark and light bands
Voluntary—conscious control over skeletal muscles
Describe cardiac muscle tissue
Cardiomyocytes are branched, shorter than skeletal muscle fibers; uninucleate
Intercalated discs join cardiomyocytes end to end
Provide electrical and mechanical connection
Striated and involuntary (not under conscious control)
Describe smooth muscle tissue
Short, fusiform myocytes; uninucleate
Non-striated and involuntary
Most is visceral muscle—making up parts of walls of hollow organs
Describe the 3 parts of the neuron
Neurosoma (cell body) -Contains nucleus & other organelles -Controls protein synthesis Dendrites -Multiple short, branched processes -Receive signals from other cells -Transmit messages to neurosoma Axon (nerve fiber) -Sends outgoing signals to other cells -Can be more than a meter long
Define cell junctions
Connections between two cells
Most cells are anchored to what?
Each other or the matrix
Describe the purpose of cell junctions
Cells communicate with each other, resist mechanical stress, and control what moves through the gaps between them
What are the 3 types of cell junctions?
Tight junctions, desmosomes, and gap junctions
Describe tight junctions and where they’re found
- Seals off intercellular space, making it difficult for substance to pass between cells
- Found in the epidermis, stomach, and small intestines
Describe desmosomes and where they’re found
- A type of cell junction that keeps cells from pulling apart—resist mechanical stress.
- Found in cardiac muscle, the uterine cervix, and the epidermis
Describe gap (communication) junctions and where they’re found
- Formed by ring-like connexons; the cells now share part of their cell membrane.
- Ions, nutrients, and other small solutes pass between cells
- Found in cardiac and smooth muscle, embryonic tissue, lens and cornea
True or false: gap junctions are absent in skeletal muscle
True
Define and describe glands
- A cell or organ that secretes substances for use elsewhere in the body or releases them for elimination from the body
- Usually composed of epithelial tissue with a connective tissue framework and capsule
Describe the differences between secretion and excretion
Secretion—product useful to the body
Excretion—waste product
Describe exocrine glands
- Maintain their contact with surface of epithelium by way of a duct
- Surfaces can be external (examples: sweat, tear glands) or internal (examples: pancreas, salivary glands)
Describe endocrine glands
-They have no ducts; instead, they secrete hormones directly into blood
Give some examples of organs that have both endocrine and exocrine responsibilities
The liver, gonads, and pancreas
Define hormones
Chemical messengers that stimulate cells elsewhere in the body
Give examples of endocrine glands
Thyroid, adrenal, and pituitary glands
Describe unicelluar glands and give examples
- Found in an epithelium that is predominantly nonsecretory
- Can be exocrine or endocrine
- Examples: mucus-secreting goblet cells in trachea or endocrine cells of stomach
What are the different characteristics we can use to describe exocrine glands?
Duct shape:
simple (unbranched) vs. compound (branched)
Gland shape:
Tubular: narrow secretory portion
Acinar: secretory cells form dilated sac (acinus or alveolus)
Tubuloacinar: both tubular and acinar portions
Describe the 3 different modes of secretion
1) Merocrine
- Uses vesicles that release their secretion by exocytosis.
- Used by eccrine glands.
2) Apocrine
- Lipid droplet covered by membrane and cytoplasm buds from cell surface
- Mode of milk fat secretion by mammary gland cells
3) Holocrine:
- Cells accumulate a product until they disintegrate
- Secrete a mixture of cell fragments and synthesized substances
- Ex: sebaceous glands of hair and skin, eyelid glands.
Describe the merocrine mode of secretion
- Uses vesicles that release their secretion by exocytosis.
- Used by eccrine glands.
Describe the apocrine mode of secretion and give an example
- Lipid droplet covered by membrane and cytoplasm buds from cell surface
- Mode of milk fat secretion by mammary gland cells
Describe the holocrine mode of secretion and give examples
- Cells accumulate a product until they disintegrate
- Secrete a mixture of cell fragments and synthesized substances
- Ex: sebaceous glands of hair and skin, eyelid glands.
True or false: Membranes may be only epithelial, only connective, or a mix of epithelial, connective, and muscular tissues
True
What is the largest membrane in the body?
Cutaneous membrane (the skin)
Define and describe the cutaneous membrane
- Cutaneous membrane (the skin) is the largest membrane in the body.
- Composed of stratified squamous epithelium (epidermis) resting on a layer of connective tissue (dermis)
- Relatively dry layer serves protective function
What are the two main types of internal membrane?
Mucous membranes and serous membranes.
Describe mucous membranes (mucosa)
- Layers consists of epithelium, areolar tissue (lamina propria), and smooth muscle (muscularis mucosa)
- Lines cavities/passages that open to the external environment
- Produces mucus (thicker, stickier)
What 4 organ systems have mucous membranes?
Reproductive, digestive, respiratory, and urinary
Describe serous membranes (serosa)
- Composed of simple squamous epithelium resting on a layer of areolar tissue
- Internal membrane; lines cavities with no connection to the outside
- Produces serous fluid
What are some membranes made up of only epithelium?
Anterior surfaces of cornea and lens of eye
What are 4 membranes made up of only connective tissues?
Dura mater (meninges)
Synovial membranes
Periosteum
Perichondrium
Define tissue growth
Increasing the number of cells or size of existing cells
Define hyperplasia
Growth through cell multiplication
Define hypertrophy and give two examples
The enlargement of preexisting cells
Examples: Muscle growth through exercise, accumulation of body fat
Define and describe neoplasia
The development of a tumor (neoplasm)
-It can be benign or malignant, and is composed of abnormal, nonfunctional tissue
What are the 3 types of tissue growth?
Hypertrophy, hyperplasia, and neoplasia
Define, describe, and give examples of the two modes of tissue repair
1) Regeneration: replacement of dead or damaged cells by the same type of cell as before
- Restores normal function
- Examples: repair of minor skin or liver injuries
2) Fibrosis: replacement of damaged cells with scar tissue
- Scar holds organs together, but does not restore function
- Examples: repair of severe cuts and burns, scarring of lungs in tuberculosis
List the steps of healing a skin wound
1) Inflammation: brings white blood cells, platelets, etc to the area. Creates swollenness, warmth, and redness.
2)Initial patch up and cleaning:
Blood clot forms; forms scab that temporarily seals the wound and blocks infection.
Macrophages clean up the scene.
3) New capillaries sprout from nearby vessels.
Fibroblasts deposit new collagen
Begins 3-4 days after the injury and lasts up to 2 weeks.
4) Regeneration, fibrosis, and remodeling: epithelial cells around the wound multiply and migrate beneath the scab (tissue regenerates)
Fibrosis: Underlying connective tissue undergoes fibrosis
Remodeling (maturation) phase begins several weeks after injury and may last up to 2 years
Categorize body tissues by how well they repair themselves into groups of good, moderate, poor, and almost no repair
Good: epithelial, bone, blood, areolar, dense irregular
Moderate: dense regular, smooth muscle
Poor: cartilage, skeletal muscle
Almost none: cardiac muscle, neurons (in CNS)
