Tissues (lecture 2) Flashcards
What is the study of tissues and how they form organs called?
Histology
The cells that form each tissue have a similar: (3)
structure, function and embryonic (germ) origin
What are the states that tissues can be (4)?
Solid (bone), semi-solid (fat), soft (muscles, ligaments), or liquid (blood)
What are the 4 tissue types?
- Epithelial (Epithelium)
- Connective
- Muscular
- Nervous
Where are most body tissues derived from?
The embryonic connective tissue Mesenchyme
What are the 3 “Embryonic” or “Germ” layers?
- Endoderm
- Mesoderm
- Ectoderm
def: Endoderm
Forms the lining of the body and digestive tract
def: Mesoderm
Forms “everything else” (muscles, ligaments, cartilage, bone, blood, etc.)
def: Ectoderm
Outer covering of the body and nervous tissue
def: Tissue
A group of cell with a common purpose: Homeostasis
Where is Epithelial tissue derived from?
All 3 germ layers, but mainly Endoderm
What are the roles of Epithelial tissue?
- Protection (Epidermis of skin)
- Filtration (Membranes for nutrient absorption)
- Secretion (Release mucous, hormones, enzymes)
- Excretion (Waste products, i.e., CO2, urine)
What are the 2 main types of epithelium (by location)
- Surface Epithelium: Lining and covering
- Glandular Epithelium: Secretory tissue in glands
What are the characteristics of Epithelium? (4)
- Cellularity: Closely packed cells + hardly any extracellular material (Matrix)
- Avascular (no blood supply of its own) + close to tissues with blood supply to be able to survive/function
- High ability to divide for repair/renewal
- Rarely covered by another tissue: has a “free” surface
def: Basement Membrane
Non-cellular layer of materials which holds the epithelia to the underlying connective tissue (+ gives strength to epithelium)
What are the 2 surfaces of the Epithelium?
Apical (free) Surface: face the body cavity, lumen, duct, etc.
Basal Surface: deepest layer (attached to the Basement Membrane)
What are the 2 layers of the Basement Membrane?
- Basal Lamina
- Closer to the actual epithelial cells
- Contains proteins laminin (glue attaching epithelial cells to the membrane) and collagen (strength) - Reticular Lamina
- Closer to underlying connective tissue
- Contains collagen (produced by connective tissue cells: fibroblasts)
What are the shapes of epithelial cells?
Squamous: flat/thin
Cuboidal: Square
Columnar: Rectangular
Transitional: Change shape (squamous/cuboidal cells that form lining of hollow organs)
What are the types of epithelium based on number of layers?
Simple Epithelium: 1 row of cells
Stratified Epithelium: multiple rows, name based on shape of Apical layer
Pseudostratified Epithelium: 1 row with diff overlapping sizes
What are the general classifications of epithelia based on shape and number of layers?
Simple: Squamous, cuboidal, columnar
Stratified: Squamous, cuboidal, columnar, transitional
Lining Epithelium: What is the function of Simple Squamous Epithelium
Allow rapid passage of substances through them
Lining Epithelium: What is the function of Simple Cuboidal Epithelium?
Secretion + Absorption
Lining Epithelium: What is the function of Simple Columnar Epithelium?
Secretion + Absorption
Lining Epithelium: What are the 2 types of Simple Columnar Epithelium?
Ciliated: Hair-like projections for filtration
Non-ciliated: can have microvilli (fixed) to increase surface area
Lining Epithelium: Describe Stratified Squamous Epithelium.
- Protective layer
- Cells replace those lost to friction
a) Apical cells further from blood: die
b) Replaced by cells at basal layer - Keratinized SSE: contain protein Keratin (tough + water resistant (epidermis))
- Non-keratinized SSE: on wet surfaces subject to wear/tear
Lining Epithelium: Describe Stratified Transitional Epithelium.
- Appearance is variable
- Mostly cuboidal/columnar w some squamous
What is an epithelial membrane comprised of and where is it found?
- Found throughout body
- Comprised of a layer of epithelium and a layer of connective tissue
What are the 2 types of Epithelial Membranes?
- Mucous Membranes
- Serous Membranes
Explain Mucous Membranes
- Secrete MUCOUS to keep linings moist
- Found in hollow organs/tracts
- Connective tissue: Lamina Propria
Explain Serous Membranes
- Line celomic (hollow) body cavities (mostly abdominopelvic cavity) + found in thoracic cavity
- Cover many viscera
- Secretes fluid for lubrication
- Visceral layer: stuck to organ wall (inner layer)
- Parietal layer: outer layer
- In btwn layers: serious fluid in cavity
What is the function of Glandular Epithelium?
Secretion
Glandular Epithelium: from where do glands develop?
Specialized epithelium
Glandular Epithelium: What is an Exocrine Gland?
If a gland (and its duct) retains a connection with surface epithelium, it will secrete externally (onto a surface)
Glandular Epithelium: What is an Endocrine Gland?
- If a gland’s ducts lose contact with surface epithelium (during development), they will secrete internally directly into the blood
- “ductless glands”
- Always secrete hormones
Describe Connective Tissue.
- Most abundant tissue
- Supports + strengthens other tissues
- Protect + insulates internal organs
- Separates structures
- Blood: transport system
- Adipose tissue: energy reserve storage
- Highly vascular (except cartilage: avascular)
- Main source of immune responses
How does Connective Tissue contrast with Epithelial?
Contains large amts of extracellular material (in which are found single cells/groups of cells)
Describe the extracellular matrix of connective tissue.
- Consists of protein fibers + ground susbtance
- Structure determines tissue’s quality
What are the states of ground substance?
Fluid, semifluid, gelatinous, calcified
(different concentrations of elastin)
What is the function of ground substance?
Support cells, bind them together, store water, provide a medium of exchange btwn blood/cells
Name the 2 most common cells associated w/ connective tissue.
Fibroblasts and Macrophages (Phagocytes)
Describe Fibroblasts.
- Large, flat cells w/ branching processes
- Form fiber for strength + structure (Mature cells: fibrocytes)
- Found in all general connective tissue, most numerous
Describe Macrophages.
- Type of phagocyte
- Move through the matrix + engulf waste products or dead cells
- Can be fixed or wandering
What are the 3 types of protein fibers found in the extracellular matrix (in ground substance) in connective tissue?
- Collagenous (White)
- Elastic (Yellow)
- Reticular (Neutral)
Connective Tissue: Describe Collagenous Fiber.
- Made from protein: Collagen
- Parallel bundles
- Strong (resist stretching/pulling)
- Non-elastic, but not stiff
- Supportive function
- Most abundant protein in body (25%)
Connective Tissue: Describe Elastic Fiber.
- Long cylindrical ribbon structure
- Made from protein: Elastin
- Surrounded by glycoprotein: Fibrillin (adds strength and stability)
- Strong but elastic (can stretch 150% and return to original)
- Abundant in skin, arterial walls, lung tissue, etc
- Found in bone
Connective Tissue: Describe Reticular Fiber.
- “immature collagen”
- Protein: reticulin
- fine bundles “cobweb”
- Non-elastic
- Form framework of organs/glands to which epithelial cells attach
- Support in walls of blood vessels
- Help form basement membrane
- Binds to smooth muscle in organs
Name the 3 types of Loose Connective Tissue
- Areolar CT
- Adipose tissue
- Reticular CT
Loose CT: Describe Areolar CT.
- Connects skin to underlying tissues, surrounds blood vessels, nerves, organs
- Provides strength, elasticity, support
Loose CT: Describe Adipose Tissue.
- Specialized function
- Found where fat is stored
- Protective, Insulation (reduce heat loss)
- Essential + non-essential fats
Loose CT: Describe Reticular CT
- Supporting framework of liver, spleen, lymph nodes, red bone marrow, blood vessels and muscles
What does Dense CT have more of compared to Loose CT?
Collagen!!
Name the 3 classifications of Dense CT.
- Dense Regular CT
- Dense Irregular CT
- Elastic CT
How does Dense Regular CT differ from Dense Irregular CT?
Dense Regular is more linear/organized.
Describe Dense Regular CT. (5)
- Collagen + fibroblasts laid down in regular fashion
- Extracellular matrix looks shiny white
- Very strong
- Forms muscle tendons, aponeuroses, and ligaments
- Provides strong attachment btwn structures
Dense Regular CT: What is the difference btwn aponeuroses, muscle tendons, and ligaments?
Tendons: attaches muscle to bone
Aponeuroses: broad, flat tendon (doesn’t anchor on bone)
Ligaments: attach bone to muscle
Dense Regular CT: Why are tendons and ligaments slow to heal after injury?
Few blood vessels
Describe Dense Irregular CT.
- Interwoven collagenous fibers + fibroblasts
- Irregularly arranged
- Found in sheets
- Forms the muscle Fascia
- Found in periosteum (bone) and perichondrium (cartilage)
- Joint capsules
- Dermis of skin
- “Leather-like”
What is Fascia
Fibrous tissue containing collagen and elastin (glides over muscle)
Dense CT: Describe Elastic CT.
- Consists of elastic fibers and fibroblasts
- Yellowish
- Allows stretching of various organs
- Elasticity: allows tissue to stretch/recoil to original shape
Describe Cartilage (CT).
- Mixture of Dense collagenous fibers and elastic fibers in a gel-like ground substance
-Strong but flexible (can endure more stress than loose/dense CT) - Very resilient, strong tensile and compression strength
- Avascular (due to secretion of an antiangiogenesis, preventing bld vessel growth)
How does Cartilage receive nutrients?
- Thru capillary network from perichondrium (covering of dense irregular CT)
- Synovial fluid in a joint
What are the 3 types of cartilage?
- Hyaline
- Fibrocartilage
- Elastic
Describe Hyaline Cartilage.
- Most of body’s cartilage
- Bluish-white, shiny
- Precursor to Bone (in embryonic stages) + only remains at ends of bone (articular cartilage)
- Strong (but weakest of all 3)
- Supportive, flexible
Describe Fibrocartilage.
- Collagenous fibers found in thick bundles w/ space btwn (matrix)
- Allows for compression
- Found in areas that support body weight (intervertebral discs, menisci of knee)
- Very strong cartilage (strongest)
- Lacks a perichondrium
Describe Elastic Cartilage.
- More flexible cartilage (most durable)
- Allows movement
- has a perichondrium
