Chapter 4: Histology Flashcards
(139 cards)
1
Q
Histology
A
Study of normal structures of tissues
2
Q
All tissues share what two basic components?
A
- Discrete population of cells, related in structure and function
- Extracellular matrix (ECM)
3
Q
Types of tissue
A
- Epithelial tissue (epithelium)
- Connective tissue
- Muscle tissue
- Nervous tissue
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Q
Epithelial tissue (epithelium)
A
- Covers a surface of lines cavities of the body
- Also forms glands
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Q
Connective tissue
A
Connects, supports, protects, insulates, and transports
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Q
Muscle tissue
A
Contracts to produce movement
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Q
Nervous tissue
A
Produces and conducts nervous impulses
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Q
Extracellular matrix
A
Substances in liquid, thick gel, or solid form that surrounds cells of tissue
9
Q
Components of extracellular matrix
A
- Ground substance
- Protein fibers
10
Q
Functions of extracellular matrix
A
- Provides tissue with strength to resist tensile and compressive forces
- Directs cells to proper positions within tissue and holds those cells in place
- Regulates development, mitotic activity, and survival of cells in a tissue
11
Q
Ground Substance
A
- Most of the ECM
- Extracellular fluid (ECF or interstitial fluid) with water, nutrients, ions, and three families of macromolecules
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Q
Families of macromolecules in ground substance
A
- Glycosaminoglycans (GAGs)
- Proteoglycans
- Cell-adhesion molecules (CAMs)
13
Q
Glycosaminoglycans (GAGs)
A
Chondroitin sulfate (small) and hyaluronic acid
14
Q
Proteoglycans
A
GAGs bound to protein core (resembles bottle brush)
- Thousands of proteoglycans bind to very long GAG to form huge proteoglycan “aggregates”
15
Q
Cell-adhesion molecules (CAMs)
A
- Difference types of glycoproteins
- Adhere cell to cell and cells to surroundings
- Hold everything in place within ECM
- CAMs bind to cell surface proteins as well as protein fibers and proteoglycans
- Maintains normal tissue architecture
16
Q
Types of protein fibers in ECM
A
- Collagen
- Reticular
- Elastic
17
Q
Collagen Fibers
A
- Most common protein in body
- Strong, flexible, inelastic
- Unbranched and arranged in bundles
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Q
Reticular Fibers
A
- Fills spaces between tissues and organs
- Fine callagenous
- Forms branching networks
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Q
Elastic Fibers
A
- Returns to its original shape after distension or compression
- Contains molecules of protain elastic that resemble coiled springs
- Molecules are cross-linked
20
Q
Cell Junctions
A
A way cells bind to one another
21
Q
Integral Proteins
A
Proteins which link neighboring cell’s plasma membranes
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Q
Types of cell junctions
A
- Tight junctions
- Desmosomes
- Gap junctions
23
Q
Tight Junctions
A
Holds cells together, forms permeability barrier
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Q
Zonula Adherens
A
- Between adjacent cells, weak glue holds cells together
- Simple epithelium
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Zonula Occludens
- Permeability barrier (e.g. stomach and urinary bladder)
| - Chemicals cannot pass between cells
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Gap Junctions
- Protein channels aid intercellular communication
- Allows ions and small molecules to pass through
- Coordinate function of cardiac and smooth muscle
- May help coordinate movement of cilia in ciliated types of epithelium
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Desmosomes
- Disk-shaped regions of cell membrane
- Often found in areas that are subjected to stress, can resist stretching and twisting
- Contains especially adhesives glycoproteins
- Intermediate protein filaments extend into cytoplasm of cells for reinforncement
- Striated squamous epithelium of the skin
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Hemidesmosomes
- Half of a desmosome
| - Attaches epithelial cells to basement membrane
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Where are epithelial tissues located?
- On EVERY internal and external body surface
- Barrier between body and external environment
- Lines organs and fluid-filled cavities
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Functions of Epithelial Tissue
- Protection: shields underlying tissues from mechanical and thermal injury
- Immune defenses: forms physical barriers to prevent invasion by microorganisms
- Secretion: forms glands that produce substances like hormones and oils; secreted into blood or through ducts respectively
- Transport into other tissues: selectively permeable membranes; substances are able to cross these barriers via passive or active transport and enter other tissues
- Sensation: most associated with rich nerve supply; detects changes in internal and external environments
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What are the implications of the avascular nature of epithelial tissue?
- They must obtain oxygen and nutrients by diffusion from deeper tissues
- This requirement limits thickness
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Components of basement membrane
- Basal lamina
- Reticular lamina
- Together these layers glue epithelial tissue and provide a barrier to underlying connective tissue
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Basal Lamina
- ECM synthesized by epithelial cells
| - Consists of collagen fibers and ground substance
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Reticular Lamina
- Synthesized by underlying connective tissue
| - Consists of reticular fibers and ground substance
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Criteria for classifying epithelial tissue
- Number of cell layers
| - Shape of cells
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Simple epithelia
Single cell layer
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Stratified epithelia
More than one cell layer
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Squamous cells
Flattened
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Cuboidal cells
Short
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Columnar cells
Tall and elongated
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Classifications of epithelial tissue
- Simple squamous
- Simple cuboidal
- Simple columnar
- Stratified squamous
- Stratified cuboidal
- Stratified columnar
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Simple Squamous Structure
Single layer of flat cells
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Simple Squamous Location
```
Lining of :
- Blood vessels
Lymphatic vessels and small ducts
- Alveoli of lungs
- Loop of Henle in kidney tubules
- Serous membrane
- Inner surface of the eardrum
```
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Simple Squamous Functions
- Diffusion
- Filtration
- Some protection against friction
- Secretion
- Absorption
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Simple Cuboidal Location
- Kidney tubules
- Sweat glands and their ducts
- Choroid plexus of the brain
- Lining of terminal bronchioles
- Surface of the ovaries
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Simple Cuboidal Structure
- Single layer of short cells
| - Some types have microvilli (kidney tubules)
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Simple Cuboidal Functions
- Secretion and absorption in the kidney
- Secretion in glands and choroid plexus
- Movement of mucus out of the terminal
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Simple Columnar Location
- Stomach
- Intestines
- Glands and some ducts
- Bronchioles of lungs
- Auditory tubes
- Uterus
- Uterine tubes
- Gallbladder
- Bile ducts
- Ventricles of the brain
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Simple Columnar Structure
- Single layer of tall, narrow cells
| - Some have cilia or microvilli
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Simple Columnar Functions
- Secretion and absorption in stomach and the intestine
- Movement of particles out of the bronchioles by ciliated cells
- Aids in movement of oocytes in the uterine tubes by ciliated cells
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Pseudostratified Columnar Epithelium
- Appears layered because nuclei are at various heights
- Only one layer thick with basal plasma membranes
- Found in trachea and nasal cavity
- Ciliated
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Stratified Squamous Locations
- Mouth
- Tongue
- Throat
- Larynx
- Esophagus
- Anus
- Vagina
- Inferior urethra
- Cornea
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Stratified Squamous Structure
Multiple layers of flat cells
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Stratified Squamous Functions
Protection against abrasion, caustic chemicals, water loss, and infection
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Keratinized
Skin
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Stratified Cuboidal Location
- Sweat gland ducts
- Ovarian follicular cells
- Salivary gland ducts
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Stratified Cuboidal Structure
Multiple layers of somewhat cube-shaped cells
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Stratified Cuboidal Functions
Secretion, absorption, and protection
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Stratified Columnar Location
- Salivary glands
- Mammary gland duct
- Larynx
- Portion of male urethra
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Stratified Columnar Structure
- Multiple layers of cells with tall thin cells resting on layers of more cuboidal cells
- Cells ciliated in the larynx
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Stratified Columnar Function
Protection and secretion
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Transitional Epithelium Location
Lining of urinary bladder, ureters, and superior urethra
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Transitional Epithelium Structure
- Stratified
| - Cells change shape depending upon amount of stretching or distention of the organ
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Gland
- Structure of epithelial origin
- Synthesizes and secretes product from designated secretory cells
- Arises from epithelial tissue that migrated into deeper connective tissue instead of remaining at the surface
- Classified by shape or by how products are released
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Endocrine Glands
Without ducts
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Exocrine Glands
With ducts
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Secretion Types
- Merocrine
- Apocrine
- Holocrine
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Merocrine Glands
- No loss of cytoplasm
- Secretion leaves by either active transport or exocytosis
- EX: sweat glands
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Apocrine Glands
- Fragments of the gland go into the secretion
- Apex of cell pinches off
- EX: mammary glands
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Holocrine Glands
- Cell ruptures and dies
- Whole cell becomes part of secretion
- Secretion accumulates in cell
- EX: Sebaceous glands
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Types of Connective Tissue
- Connective tissue proper
- Fluid connective tissue
- Supporting connective tissue
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Types of connective tissue proper
- Loose (areolar)
- Dense
- Reticular
- Adipose
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Types of fluid connective tissue
- Blood
| - Lymph
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Types of supporting connective tissue
- Cartilage
| - Bone
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Connective Tissue Functions
- Connecting and binding: anchor tissue layers in organs and link organs together
- Support: bone and cartilage support body weight
- Protection: bones protect internal organs, cartilage and fat absorb shock
- Transport: blood
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Connective tissue proper
- Syrupy ground substance
- Contains varied cell populations
- Various fiber types
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Fluid connective tissue
- Dense ground substance
| - Less diverse cell population
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Supporting connective tissue
- Watery ground substance with dissolved proteins
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Blasts
Create the matrix
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Cytes
Maintain the matrix
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Clasts
Break the matrix down for remodeling
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Hyaluronic acid
- Polysaccharide
- Good lubricant
- Vitreous humor of the eye
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Proteoglycans
- Protein and polysaccharide
- Protein part attaches to hyaluronic acid
- Traps large amounts of water
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Adhesive molecules
- Hold proteoglycan aggregates together
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Loose Connective Tissue
- Loose packing material of most organs and tissues
- AKA stroma
- Attaches skin to underlying tissues
- Contains collagen, reticular, elastic fibers, and all five types of cells
- Cells include fibroblasts, mast cells, lymphocytes, adipose cells, and macrophages
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What is included in the superficial fascia?
- Epidermis, dermis, and hypodermis or subcutaneous layer
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Dense Regular Connective Tissue
- Parallel, tightly packed collagen fibers
- Has abundant collagen fibers that resist stretching
- Tendons and ligaments
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Tendons
- Connects muscles to bones
| - Fibers are not necessarily parallel
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Ligaments
- Connects bones to bones
- Collagen often less compact, usually flattened
- Forms sheets or bands
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Dense Irregular Collagenous Connective Tissue
- Collagen fibers arranged in a randomly oriented network
- Forms innermost layer of the dermis of the skin, scars, capsules of kidney and spleen
- Allows tissue to tolerate extension and recoil
- Elastic ligaments help stabilize the positions of the vertebrae in the spinal column
- In walls of elastic arteries
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Reticular Connective Tissue
- Forms find 3D networks that support small structures (blood and lymphatic vessels) called stroma
- Mostly reticular fibers produced by fibroblasts
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Adipose Connective Tissue
- Fat-storing adipocytes and surrounding fibroblasts and ECM
| - Can increase in size to a point where fibroblasts and ECM are scarcely visible
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Functions of adipose tissue
- Fat storage (major energy reserve of the body)
- Insulation (retains warmth)
- Shock absorption and protection
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Types of adipose tissue
- Yellow
| - Brown
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Yellow Adipose Tissue
- Most abundant type, has wide distribution
| - What at birth and yellows with age
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Brown Adipose Tissue
Found only in specific areas of the body:
| - Axillae, neck, and near kidneys
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Cartilage Tissue
- Cells are called chondrocytes located in matrix-surrounded spaces called lacunae
- Avascular and no nerve supply
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Ground substance of cartilage
Proteoglycans and hyaluronic acid with large amounts of water
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Perichondrium
- Separates cartilage from surrounding tissues
- Dense irregular connective tissue that surrounds cartilage
- Fibroblasts of perichondrium can differentiate into chondroblasts
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Types of cartilage
- Hyaline
- Fibrocartilage
- Elastic
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Hyaline Cartilage
- Most common type
- Avascular
- Glassy appearance and contains collagen (not easily seen)
- Reduce friction and provide shape
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Hyaline cartilage location
- B/t tips of ribs and bones of sternum
- Covering bone surfaces at synovial joints
- Supports larynx, trachea, and bronchi
- Forms part of nasal septum
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Hyaline cartilage function
- Provides stiff but somewhat flexible support
| - Reduces friction between bony surfaces
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Fibrocartilage Structure
- Thick collagen fibers distributed in proteoglycan matrix
| - Slightly compressible and very tough
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Fibrocartilage Locations
- Found in areas of body where a great deal of pressure is applied to joints
- Knee, jaw, intervertebral disk
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Fibrocartilage Functions
- Resists compression
- Prevents bone-to-bone contact
- Limits relative movement
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Elastic Cartilage Structure
- Elastic and collagen fibers embedded in proteoglycans
| - Rigid by elastic properties
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Elastic Cartilage Locations
External ears and epiglottis
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Elastic Cartilage Functions
- Involved in flexible support
| - Avascular
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Bone Connective Tissue
- Hard connective tissue composed of living cells (osteocytes) and mineralized matrix
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Bone Matrix
- Gives strength and rigidity
| - Allows bone to support and protect other tissues and organs
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Types of bone
- Cancellous or spongy bone
| - Compact bone
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Osteocytes
- Osteoblasts that have surrounded themselves with ECM in lacunae
- Mature cells, mostly inactive
- Continue to make and secrete substances important for bone maintenance
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Osteoblasts
- "Bone-builders" on outer surface of bones
- Closely associated with dense irregular collagenous connective tissue covering (periosteum)
- Carry out process of bone deposition
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Osteoclasts
- Large, multinucleated bone destroyers
- Carry out process of bone resorption
- Secrete hydrogen ions enzymes that break down both inorganic and organic ECM
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Hemopoietic Tissue
Forms blood cells, found in bone marrow
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Types of bone marrow
- Red
| - Yellow
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Red bone marrow
- Hemopoietic tissue surrounded by a framework of reticular fibers
- Produces red and white cells
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Yellow bone marrow
- Yellow adipose tissue
| - As children grow, yellow marrow replaced much of red marrow
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Blood
- ECM is fluid
- Plasma proteins
- Erythrocytes
- Leukocytes
- Platelets
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Plasma proteins
- Not like fibers found in other connective tissues
| - Smaller with a variety of functions, including transport of substances and blood clotting
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Erythrocytes
Bind to and transport oxygen throughout body
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Leukocytes
Function in immunity
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Platelets
- Cell fragments
| - Major role in blood clotting
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Characteristics of muscle tissue
- Contracts or shortens with force
| - Moves entire body and pumps blood
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Types of muscle tissue
- Skeletal
- Cardiac
- Smooth
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Skeletal Muscle
- Most attached to skeleton
- Some attached to other types of connective tissue
- Striated and voluntary
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Cardiac Muscle
- Muscle of the heart
- No conscious control
- Cells are short, branched
- Striated and involuntary
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Smooth Muscle
- Muscle associated with tubular structures and with the skin
- Flattened cells with one centrally located ovoid nucleus
- Neighboring cells are linked together by gap junctions
- Nonstriated and involuntary
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Intercalated disc
- Dark line separating individual cardiac muscle cells
- Contains gap junctions and modified tight junctions
- Heart muscle contracts as unit
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Nervous Tissue
- Makes up majority of brain, spinal cord, and nerves
| - ECM is unique, ground substance has unique proteoglycans and contains few protein fibers
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Main cell types in nervous tissue
- Neurons
| - Neuroglial cells
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Neurons
Capable of sending and receiving messages
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Neuroglial Cells
- Performs various functions
- Supports neuron activities
- Able to dividid by mitosis
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Functions of Neuroglial cells
- Anchoring neurons and blood vessels in place
- Monitoring composition of extracellular fluid
- Speeding up rate of nerve impulse transmission
- Circulating fluid surrounding brain and spinal cord
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Types of membranes
- Mucous
- Serous
- Synovial
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Mucous Membrane
- Secrete mucus
- Contains epithelium with goblet cells, basement membrane, lamina propria (sometimes with smooth muscle)
- Found in respiratory, digestive, urinary, and reproductive systems
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Serous Membrane
- Simple squamous epithelium called mesothelium, basement membrane, thine layer of loose connective tissue
- Lines cavities not open to the exterior
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Synovial Membrane
- Lines freely moveable joints
| - Produces fluid rich in hyaluronic acid
