Chapter 4 - The Tissue Level of Organization Flashcards
What is a Tissue?
A Tissue is a group of cells that usually have a common embryonic origin
Function together to carry out specialized activities
4 Types in body:
1- Epithelial
2- Connective
3- Muscular
4- Nervous
What is a Cell Junction?
A cell Junction is a point of contact between cells
Holds cells together
What is a Tight Junction?
Impermeable junction that form continuous seals around cells to prevent molecules from passing through Intracellular space
Function:
Prevent substances from passing between cells
Requires materials to move through rather than between cells
Prevents leakage of urine
What is a Desmosome?
Anchoring junction that bind adjacent cells together
Composed of proteins that bind neighboring cells
Function:
Helps form internal tension-reducing network of fibers
Provides integrity to cells exposed to stress
What is a Hemidesmosome?
Anchors basal layer of cells of epidermis to underlying components
What is a Gap Junction?
Composed of proteins called Connexons
Function:
Form tiny, fluid-filled tunnels between cells
Provide direct passageway for substances like ions and small molecules to travel between cells
ex: flow of ions between cells of cardiac muscle
What is an Adherens Junction
Junction between cells made of an Adhesion Belt
Adhesion Belt made of a plaque of Actin microfilaments on the outside and Transmembrane Glycoprotein (Cadherin) on the inside of it
Function:
Initiation and stabilization of cell-cell adhesion
Regulation of the actin cytoskeleton
Intracellular signaling
Transcriptional regulation
What is Epithelial Tissue?
Cells arranged in sheets and densely packed
Many cell junctions present
Epithelial cells attached to Basement membrane
Epithelial tissue is avascular but does have a nerve supply
Mitosis occurs frequently
What is the Structure of Epithelial Cells and Basement Membrane?
Epithelium:
Apical Surface - top part
Lateral Surface - between 2 cells
Avascular, but innervated
Basement Membrane:
Basal Lamina (top)
Reticular Lamina (bottom)
Avascular, but innervated
Connective Tissue:
Deep to the Basement Membrane
Contains Blood vessels
What are the Types of Arrangement of Layers of Epithelial Tissue?
Simple
Pseudostratified (Columnar)
Stratified
Transitional (Stratified at bottom and Simple on top)
What are the Types of Shapes of Cells of Epithelial Tissue?
Squamous
Cuboidal
Columnar
What is Glandular Epithelium?
Gland:
A single cell or mass of epithelial cells adapted for secretion
What is an Endocrine Gland?
Endocrine Glands:
No ducts
Secretions (hormones) enter the interstitial fluid and diffuse into bloodstream
ex:
Pituitary Gland
Pineal Gland
Thyroid and Parathyroid Glands
Adrenal Glands
Pancreas
Ovaries and Testes
Thymus
Function:
Hormones regulate many metabolic and physiological activities to maintain homeostasis
What is an Exocrine Gland?
Exocrine Glands:
Secretions enter ducts that empty on the surface of a covering/lining epithelium (such as skin surface of lumen of stomach)
ex:
Sweat, oil, and earwax glands of skin
Digestive glands like Salivary Glands and Pancreas
Function:
Produce substances such as sweat to help lower body temperature, oil, earwax, saliva, or digestive enzymes
What is the Structural Classification of Glandular Epithelium?
Unicellular - Goblet Cells
Multicellular - composed of many cells that form a distinctive structure
Sweat glands
Oil glands
Salivary glands
What are the Forms of Multicellular Exocrine Glands?
All made of a duct and a secretory portion
Simple Tubular - Intestinal glands
Simple Branched Tubular - Stomach (gastric) glands
Simple Coiled Tubular
Simple Acinar
Simple Branched Acinar - Sebaceous (oil) glands
Compound Tubular - Duodenal glands of small intestine
Compound Acinar - Mammary glands
Compound Tubuloacinar - Salivary glands
What are the Functional Classifications of Glandular Epithelium?
Merocrine Secretion:
Secretory vesicles release secretions out of cell (Exocytosis)
Apocrine Secretion:
Pinches off portion of cell as secretion
Holocrine Secretion:
Mature cell dies and becomes secretory product
Cell division replaces lost cell
What is Connective Tissue?
Connective Tissue composed of Cells and Extracellular Matrix
Connective Tissue cells don’t have any free surfaces
Highly vascularized and has nerve supply
(Exceptions: Tendons and Cartilage)
What are some Connective Tissue Cells?
Fibroblasts
Reticular Fibers
Collagen Fiber
Elastic Fibers
Ground Substance
Adipocytes
Macrophages
Eosinophils
Neutrophils
Plasma Cells
Mast Cells
What is Fibroblast?
Large flat cells
Secrete Fibers and Ground Substance
What is Reticular Fiber?
Made of Collagen and Glycoproteins
Provide support in blood vessel walls
Form branching network around various cells (fat, nerve, smooth muscle)
What is Collagen Fiber?
Strong, flexible bundles of protein Collagen
Most abundant in body
What is Elastic Fiber?
Stretchable but strong fibers made of proteins, Elastin, and Fibrillin
Found in skin, blood vessels, and lung tissue
What is Ground Substance?
Material between cells and fibers
Made of water and organic molecules (Hyaluronic acid, Chondroitin Sulfate, Glucosamine)
Supports cells and fibers, binds them together
Provides medium for exchanging substances between blood and cells
What is Adipocyte?
Fat cells
Store fats
Found below skin and around organs (heart, kidney)
What is Macrophage?
Develop from Monocyte
Destroy bacteria and cell debris by Phagocytosis
What is Eosinophils?
WBC that migrates to sites of parasitic infection and allergic responses
What is Neutrophils?
WBC that migrates to sites of infection
Destroy microbes by Phagocytosis
What is Plasma Cells?
Develop from B Lymphocyte
Secrete antibodies that attack and neutralize foreign substances
What is Mast Cells?
Abundant in blood vessels
Produce Histamine, which dilates small blood vessels during inflammation
Kills bacteria
What is Connective Tissue Extracellular Matrix?
Extracellular Matrix located in spaces between connective tissue cells
Composed of Fibers and Ground Substance
What do Fibers do in Extracellular Matrix?
Provide strength and support a tissue
What are the Classifications of Connective Tissue?
1- Embryonic:
Mesenchyme
Mucous
2- Mature:
Loose
Dense
Cartilage
Bone
Blood
What are Membranes?
Membranes are flat sheets of pliable tissue that cover or line part of the body
2 Types:
1- Epithelial Membranes:
Mucous Membrane
Serous Membrane
Cutaneous Membrane
2- Synovial Membrane
What does Mucous Membrane do?
Line body cavities that open to outside
What does Serous Membrane do?
Line cavities that do not open directly to outside
What does Cutaneous Membrane do?
Skin covers the surface of the body
What does Synovial Membrane do?
Line joints, secrete Synovial fluid (to reduce friction)
What is Muscular Tissue?
Muscular Tissue consists of fibers that provide motion, maintain posture, and produce heat
3 Types:
Skeletal
Cardiac
Smooth
What is Nervous Tissue?
2 Types of cells:
Neurons
Neuroglia
What does Neuron do?
Neuron has a cell body, dendrites, and axons
Carry sensory or motor information
Perform integrative functions
What does Neuroglia do?
Neuroglia protects and supports Neurons
What are Excitable Cells?
Neurons and Muscle Fibers are excitable cells because they exhibit electrical excitability
Electrical Excitability is ability to respond to certain stimuli by producing electrical signals, such as action potentials, which travel along plasma membrane of a neuron or muscle fiber due to the presence of specific voltage-gated channels
What is Tissue Repair?
Process that replaces worn-out, damaged, or dead cells
Epithelial cells replaced by division of stem cells (undifferentiated cells)
Not all connective tissue cells have ability to repair:
Muscle cells can perform limited repair
Some nervous cells can perform limited repairs, others can’t
What is Fibrosis?
The formation of scar tissue
How does Tissue Repair work?
Regeneration:
Replacement of damaged or dead cells with same cell type
Restores organ function
Fibrosis:
Gap filled with scar tissue
Collagen produced by Fibroblasts
Functional activities not restored
What are the Stages of Wound Healing?
Cut blood vessels bleed into wound
1- Blood Clot forms and Leukocytes clean wound
Clot is temporary barrier for pathogens
2- Blood vessels re-grow and Granulation tissue forms
Vascular connective tissue initially forms in wound
3- Epithelium regenerates and connective tissue Fibrosis occurs
Wound Healing is dependent on extent of injury
Longer for deeper wider surfaces
With severe damage, less likely to return to original condition
Hair follicles, exocrine glands, nerves, and arrector pili muscle cells not repaired
What is Simple Squamous Epithelium?
Single layer, disc shaped central nuclei
Function:
Allows material to pass by diffusion
Filtration in sites where protection not important
Secretes lubricating substances in serosae
Location:
Kidney glomeruli
Air sac of lungs
Lining of heart, blood vessels, lymphatic vessels
Lining of ventral body cavity (Serosae)
What is Simple Cuboidal Epithelium?
Single layer cubelike cells, large spherical central nuclei
Function:
Secretion
Absorption
Location:
Kidney tubules
Ducts and secretory portions of small glands
Ovary surface
What is Simple Columnar Epithelium?
Single layer tall cells, round/oval nuclei
Many have microvilli
Some have cilia
Layer may contain Goblet Cells (mucus secreting unicellular gland)
Function:
Absorption
Secretion of mucus, enzymes, and other substances
Ciliated type propels mucus (or reproductive cells) by ciliary action
Location:
1- Nonciliated type:
Lines most of GI tract
Gallbladder
Excretory ducts of some glands
2- Ciliated variety:
Lines small bronchi
Uterine Tubes
Some regions of Uterus
What is Pseudostratified Columnar Epithelium?
Single layer of cells of differing heights, some not reaching free surface
Nuclei seen at different levels
May contain Goblet Cells and bear cilia
Function:
Secrete substances (particularly mucus)
Propulsion of mucus by ciliary action
Location:
1- Nonciliated type:
Male’s sperm-carrying ducts
Ducts of large glands
2- Ciliated variety:
Lines Trachea
Most upper Respiratory tract
What is Stratified Squamous Epithelium?
Thick membrane composed of several cell layers
Basal cells are cuboidal or columnar and metabolically active
Surface cells are flattened
Keratinized type: Surface cells are full of Keratin and dead
Basal cells are active in mitosis and produce more superficial layers
Function:
Protect underlying tissues in areas subjected to abrasion
Location:
1- Nonkeratinized type:
Forms the moist linings of Esophagus, Mouth, and Vagina
2- Keratinized type:
Forms Epidermis of skin, a dry membrane
What is Transitional Epithelium?
Resembles both stratified squamous and stratified cuboidal
Basal cells are cuboidal or columnar
Surface cells are dome shaped or squamous-like depending on degree of organ stretch
Function:
Stretches readily
Permits stored urine to distend urinary organ
Location:
Lines the Ureters
Bladder
Part of Urethra
What are the Types of Loose Connective Tissue?
Areolar
Adipose
Reticular
What are the Types of Dense Connective Tissue?
Regular
Irregular
Elastic
What are the Types of Cartilage Tissue?
Hyaline
Elastic
Fibrocartilage
What are the Loose Areolar Connective Tissue?
Gel-like matrix
All 3 types of fibers
Cells: Fibroblasts, Macrophages, Mast Cells, and some WBC
Function:
Wraps and cushions organs
Its macrophages phagocytize bacteria
Plays important role in inflammation
Holds and conveys tissue fluid
Location:
Widely distributed under epithelium
Forms Lamina Propria of mucus membranes
Packages organs
Surrounds capillaries
What are the Loose Adipose Connective Tissue?
Gel-like matrix
All 3 types of fibers
Cells: Fibroblasts, Macrophages, Mast Cells, and some WBC
But very sparse
Closely packed Adipocytes have nucleus pushed to the side by large fat droplet
Function:
Provides reserve food fuel
Insulates against heat loss
Supports and protects organs
Location:
Under skin in Subcutaneous tissue
Around Kidneys and Eyeballs
Within Abdomen
In Breasts
What are the Loose Reticular Connective Tissue?
Loose network of reticular fibers in gel-like ground substance
Reticular cells lie on the network
Function:
Fibers form a soft internal skeleton (Stroma) that supports other cell types including WBC, Mast Cells, and Macrophages
Location:
Lymphoid organs (Lymph Nodes, Bone Marrow, and Spleen)
What are the Dense Regular Connective Tissue?
Primarily parallel Collagen Fibers
Few Elastic Fibers
Major cell type is Fibroblast
Function:
Attaches muscles to bones or to muscles (tendons)
Attaches bones to bones (ligaments)
Withstands great tensile stress when pulling force is applied in one direction
Location:
Tendons
Most Ligaments
Aponeuroses
What are the Dense Irregular Connective Tissue?
Primarily irregularly arranged Collagen Fibers
Some Elastic Fibers
Major cell type is Fibroblast
Function:
Withstands tension exerted in many directions
Provides structural strength
Location:
Fibrous capsules of organs and joints
Dermis of skin
Submucosa of Digestive tract
What are the Dense Elastic Connective Tissue?
Dense regular connective tissue containing high proportion of Elastic Fibers
Function:
Allows tissue to recoil after stretching
Maintains pulsatile flow of blood through arteries
Aids in passive recoil of lungs following inspiration
Location:
Walls of large arteries
Within certain ligaments associated with the vertebral column
Within walls of the bronchial tubes
What are the Hyaline Cartilage Connective Tissue?
Amorphous but firm matrix
Collagen fibers form imperceptible network
Chondroblasts produce the matrix
When mature (Chondrocytes) lie in Lacunae
Function:
Supports and reinforces
Serves as resilient cushion
Resists compressive stress
Location:
Forms most of the embryonic skeleton
Covers the ends of long bones in joint cavities
Forms costal cartilages of the ribs
Cartilages of the Nose, Trachea, and Larynx
What are the Elastic Cartilage Connective Tissue?
Amorphous but firm matrix
Collagen fibers form imperceptible network
Chondroblasts produce the matrix
When mature (Chondrocytes) lie in Lacunae
More Elastic Fibers in matrix than in Hyaline Cartilage
Function:
Maintains shape of a structure while allowing great flexibility
Location:
Supports the external ear (Pinna)
Epiglottis
What are the Fibrocartilage Cartilage Connective Tissue?
Amorphous but firm matrix
Collagen fibers form imperceptible network
Chondroblasts produce the matrix
When mature (Chondrocytes) lie in Lacunae
Matrix less firm than in Hyaline Cartilage
Thick Collagen Fibers predominate
Function:
Tensile strength allows it to absorb compressive shock
Location:
Intervertebral Discs
Pubic Symphysis
Discs of the knee joint
What is Osseous Tissue?
Bones
Hard, calcified matrix containing many Collagen Fiber
Osteocytes in Lacunae
Very well vascularized
Function:
Supports and protects
Provides levers for the muscles to act on
Stores calcium and other minerals and fat
Marrow inside bones is site for Hematopoiesis (Blood cell formation)
Location:
Bones
What are the 2 types of Bones?
Compact Bone:
Perforated by neurovascular canals
Cylindrical structures - Osteons
Spongy Bone:
Located in interior of bone
Latticework structure, strong, and lightweight
What is Blood Tissue?
RBC and WBC in Plasma (fluid matrix)
Function:
Transport respiratory gases, nutrients, wastes, and other substances
Location:
Contained within blood vessels
What is Muscular Tissue?
Skeletal Muscle
Cardiac Muscle
Smooth Muscle
What is Skeletal Muscle?
Long, cylindrical, multinucleated cells
Obvious striations
Function:
Voluntary movement
Locomotion
Manipulation of the environment
Facial expression
Voluntary control
Location:
In skeletal muscles attached to bones or occasionally to skin
What is Cardiac Muscle?
Branching, striated, generally uninucleate cells that interdigitate at specialized junctions - Intercalated Discs
Function:
As it contracts it propels blood into circulation
involuntary control
Location:
Walls of heart
What is Smooth Muscle?
Spindle-shaped (elongated) cells with central nuclei
No striations
Cells arranged closely to form sheets
Function:
Propel substances or objects (food, urine, baby) along internal passageways
Involuntary control
Location:
Mostly in walls of hollow organs
What is Nervous Tissue?
Neurons are branching cells
Cell processes that may be quite long extend from nucleus-containing cell body
Also contributing to nervous tissue are nonexcitable supporting cells
Function:
Neurons transmit electrical signal from sensory receptors and to effectors (muscles and glands)
Supporting cells support and protect neurons
Location:
Brain
Spinal Cord
Nerves
