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Histology Kristopher Piceno - Coggle Diagram
Histology
Kristopher Piceno
Epithelial Tissues
- form protective coverings and are the ones responsible for secretion and absorption
characteristic
Widespread throughout the body
Cover organs and the body surface, line cavities and hollow organs, and make up glands
Have a
apical
surface exposed to the outside or internally
to an open space
Apical
= Free surface
Anchored to underlying connective tissues by a **basement membrane
Made up of tightly packed cells containing little intercellular materials
Readily divide
Lack blood vessels, but are nourished by cells in underlying connective tissues
Types of Epithelial Tissues
- Classified by cell shape and layers
Classification/
Appearance
Cell Shapes
Cuboidal
- cube-shaped cells
Columnar
- tall and elongated cells
Squamous
- thin and flattened cells
Number of Layers
Simple
- A single layer of cells
Stratified
- literally anything more than 1, so 2 or more cells
*Free surfaces can be modified to reflect specific functions, such as presence of cilia or microvilli
Simple Layers
Simple Cuboidal Epithelium
Locations:
Lines most kidney tubules, covers ovaries, and lines ducts of some glands
Function:
Functions in urine formation in the kidneys, and glandular secretion
*When it lines tubules or ducts, free surface faces lumen, a hollow channel
Classification:
single layer of cube-shaped cells with centrally located nuclei
Simple Squamous Epithelium
Classification/Appearance:
Made up of a single layer of thin, flattened cells. Cells are tightly packed together and have broad, thin nuclei.
Location:
This type is found in diffusion and filtration sites
Function:
Manages the exchange of gases in the alveoli of the lungs, and lines blood and lymph vessels, as well as body cavities
*It is very delicate, and can be damaged easily
Simple Columnar Epithelium
Classification/Appearance:
Is made up of one row of tall, elongated cells with nuclei near the basement membrane
Cilia:
are long extensions from the surface of certain cells, the beat in a certain direction to move cells or mucus.
Ciliated cells
Location:
found in the uterine tubes
Function:
help move egg cells toward the uterus
*some contain tiny microvilli (smaller than cilia) to increase surface area for absorption
Goblet cells
Function:
secrete mucus onto the free surface of the tissue for lubrication or protection
Location:
scattered among the cells
Nonciliated Cells
Function:
protect underlying tissues, secrete digestive fluids, and absorb nutrients
Location:
line the uterus, stomach, and intestines
*contains no microvilli
Pseudostratified Columnar Epithelium
Classification/Appearance:
appear layered due to the varying positions of their nuclei within the row of cells,
but are not truly layered.
Cells vary in shape and most of the cells reach the basement membrane, but not all reach the surface
*Most cells have cilia along their free surface. These cells contain goblet cells that secret mucus
Location:
Found in the passageways of the respiratory system
Function:
In the respiratory tract, the mucus traps dust and microorganisms, and the cilia sweep them away from the airways
Pseudostratified Columnar Epithelium
Classification/Appearance:
appear layered due to the varying positions of their nuclei within the row of cells, but are not truly layered, ALL cells reach the basement membrane, contain Goblet cells
*have cilia along their free surface
Location:
in the passageways of the respiratory system
Fucntion:
mucus traps dust and microorganisms, and the cilia sweep them away from the airways
Stratified Layers
Stratified Squamous Epithelium
Classification/Appearance:
Made up of many layers of flattened cells, designed to protect underlying layers, cuboidal cells in the deeper layers divide, and push the older cells outward, where they begin to flatten
Location:
Makes up the outer layer of skin (epidermis), and lines the mouth, esophagus, vagina, and anal canal
*keratinization:
In skin, outer layer cells die and produce a dry, water-proof, protective layer
does not occur in areas in which tissues remain
moist and alive: oral cavity, esophagus, vagina, or anal canal
Function:
designed to protect underlying layers
Stratified Cuboidal Epithelium
Classification/Appearance:
Consists of 2 to 3 layers of cuboidal cells
Location:
Forms lining of a lumen. Lines ducts of the mammary glands, sweat glands, salivary glands, pancreas, ovarian follicles, and seminiferous tubules
Function:
Provides greater protection than a single cell layer
Stratified Columnar Epithelium
Classification/Appearance:
Consists of several layers of cells, Has columnar cells on the surface and cuboidal cells in the basal layers
*A rare type of tissue
Location:
Found in the male urethra and linings of large gland ducts
Transitional Epithelium
Location:
in the linings of the urinary bladder, urethra, and ureters
Function:
an expandable lining, and prevents urine from diffusing back into the internal environment, Stretchability, protection
Connective Tissues
- Support soft parts and binds certain structures together
General characteristics
lie far apart
Bind, support, protect, serve as frameworks, fill spaces, store fat, produce blood cells, protect against infection, and help repair tissue damage
Have an abundance of extracellular matrix, or intercellular material, composed of protein fibers and ground substance
Consistency varies from liquid to rigid, depending on the ground substance
can divide
have a good blood supply (except cartilage)
Cell Types of Connective Tissues
Mast cells:
large, fixed cells, located near blood vessels; release heparin (anticoagulant) and histamine (promotes inflammation)
Fibroblasts:
most common fixed cell type; large, star-shaped
cells that secrete fibers
Produce the 3 types of fibers found in connective
tissues
Elastic (yellow) fibers:
made of the protein elastin; occur in thin branching fibers arranged in a network; stretchy and add flexibility to certain types of connective tissues; example: vocal cords
Reticular fibers:
thin collagen fibers that form branching, supportive networks in a variety of tissues; example: spleen
Collagen (white) fibers:
thick threads of collagen protein; found in long, parallel bundles; high tensile strength to hold structures together, but not very elastic; examples: tendons, ligaments
Categories of Connective Tissue
Connective tissue proper
Loose connective tissue
Areolar tissue
Locations:
binds skin to underlying tissues, under most epithelial layers, between muscles
Appearance:
Matrix consists of a gel-like ground substance containing collagen and reticular fibers
Main cell type is fibroblasts
Forms thin, delicate membranes
Adipose tissue (fat)
Appearance:
Contains adipocytes, which store fat in cytoplasm
Location:
Found under skin, between muscles, around kidneys, around abdominal membranes, behind eyeballs
Functions:
Cushions joints & organs, stores energy, insulates body
Reticular connective tissue
Appearance:
Contains thin, reticular fibers that form a 3-dimensional network
Location:
Forms a framework for certain internal organs (liver, spleen)
Dense connective tissue
:
Appearance:
Consists of densely packed collagen fibers and a network of elastic fibers
Does not have many cells; most are fibroblasts
Due to strength of collagen fibers, the tissue can withstand
pulling forces
Has a poor blood supply, so heals slowly
Location:
Found in tendons, ligaments, deep layer of skin, and the white layer of the eyeball (sclera)
Specialized connective tissue
Cartilage
A rigid connective tissue
Provides a supportive framework for various structures, protects underlying tissues, serves as models for developing bones
Lacks a vascular system, so heals slowly, and cells do not divide often
Abundant matrix, with collagen fibers in a gel-like ground substance
Chondrocytes (cartilage cells) lie within lacunae (chambers) in the matrix
Cartilaginous structures are enclosed within a connective tissue covering called the perichondrium
The 3 types of cartilage differ by their type of matrix
Hyaline cartilage
The most common type of cartilage
Contains fine collagen fibers in matrix; appears glassy
Found on the ends of bones, supports respiratory structures and passages, also important in embryonic development of many bones and bone growth
Elastic cartilage
Contains elastic fibers in dense network; flexible
Provides framework for the external ears and parts of the larynx
Fibro cartilage
Tough tissue containing many collagenous fibers
Good shock absorber
Found in intervertebral discs, knees and pelvic girdle
Bone
The most rigid connective tissue, due to presence of mineral salts (calcium salts)
Collagen fibers within the matrix provide some flexibility
Bone supports and protects many body structures in cranial & thoracic cavities
Forms sites for muscle attachments
Site of blood cell formation (red bone marrow)
Stores and releases chemicals, such as calcium and phosphorus
2 types of bone tissue
compact
Bone cells, called osteocytes, lie within lacunae (chambers)
Matrix is arranged in concentric circles (lamellae) around central or Haversian canals
Cylindrical units are called osteons or Haversian systems
Central canals contain blood vessels, and distribute blood to the cells through tiny tubes called canaliculi
Bone has a good blood supply, enabling rapid recovery after an injury
spongy
Blood
Functions to transport substances throughout the body
Transports substances between interior cells and cells that exchange nutrients, gases, and wastes with the environment
Composed of formed elements suspended in a liquid matrix called plasma
Formed elements include red blood cells to carry oxygen, white blood cells for protection against infection, and platelets for blood clotting
Most blood cells are produced by the red bone marrow within certain long bones
Muscular Tissues
- Responsible for body movement
General characteristics of muscle tissues
Muscle cells, or muscle fibers, have ability to generate force, contract and shorten to provide movement
3 types of muscle tissue:
Skeletal Muscle Tissue
Makes up muscles that attach to bones
Voluntary; can be controlled by conscious effort
Cells (fibers) are long and cylindrical, striated (have a striped appearance), have many nuclei
Cells contract only when stimulated by nerve cells (neurons)
Skeletal muscles move head, trunk, and limbs
Smooth Muscle Tissue
Named because smooth muscle cells lack striations
Cells are spindle-shaped, with 1 central nucleus
Involuntary, since it cannot be stimulated to contract with
conscious effort
Found in the walls of hollow internal organs, such as in the digestive tract, blood vessels, and urinary bladder
Cardiac Muscle Tissue
Found only in the heart
Consists of branching cells (fibers), each with a single nucleus
Cells form branching networks
Cells are connected to each other by intercalated discs containing special gap junctions that send impulses from cell to cell
Involuntary; cannot be controlled by conscious effort
Striated; has a striped appearance
Makes up most of the heart
Pumps blood through heart and into blood vessels
40% of body weight is skeletal muscle, and 10% is smooth and
cardiac muscle
Nervous Tissues
- Conduct impulses to control and coordinate body activities
Found in the brain, spinal cord, and nerves
Neurons:
nerve cells
Cells that respond to certain types of environmental stimuli or changes,
Consist of a soma (cell body), and cellular processes (extensions), called dendrites (receive stimuli) and axons (send out signals)
Coordinate and regulate body functions
Neuroglia:
nerve glue
Cells that support, nourish, and communicate with neurons, but do not conduct impulses
Bind nervous tissue together, conduct phagocytosis
Glands
Endocrine
secrete into body fluids or blood
Exocrine
secrete products into ducts that open to a body surface
Types of Membranes
Epithelial membranes:
thin, sheet-like structures composed of epithelium and connective tissues, covering body surfaces and lining body cavities; there are 3 types
Serous membranes
Line cavities that do not open to the outside (thoracic and abdominal cavities)
Consist of simple squamous epithelium and a layer of areolar connective tissue
Examples: pleura, pericardium, and peritoneum
Exist as double-layered membranes
Outer parietal portion:
lines the cavity wall
Inner visceral portion:
covers the organs
Contain a small amount of lubricating serous fluid between the 2 layers,
which is secreted by cells of the membrane
Mucous membranes
Line cavities and tubes that open to the outside of body
Consist of some type of epithelium and a layer of areolar connective tissue
Contain goblet cells that produce mucus
Include oral and nasal cavities, and tubular organs of the digestive, respiratory, urinary, and reproductive systems
Cutaneous membrane
The skin
dry membrane that is keratinized for protection and water-proofing
Connective tissue membranes
Synovial membranes
Line joints and are composed entirely of connective tissue