Chapter 4 Hostology
4.1 Introductions to Tissues
Tissue- group of structurally and functionally related calls and their external environment that together perform common functions (chemical->cellular->Tissue)
Histology- the study of the normal structure of tissues
two basic components
a discrete population of cells that are related in structure and function.
a surrounding material called the Extracellular Matrix, differs in composition in each tissue type.
4 primary tissue types
Epithelial tissues (4)- sheets of tightly packed cells with little ECM.
covers and lines body surfaces and cavities and form parts of gland
Connective Tissue (4)- connects all other tissues together
cells are scattered through the large amount of ECM
bind, support, protect, and allow transport of substances
Muscular Tissue (3)- cells contract and generate force; little ECM
Nervous Tissue (2)- cells (neurons) generate, send , and receive messages: including cells that support the neurons with a unique ECM
Cell Junction- connections of neighboring cells in a tissue linked to one another by integral proteins
Three types:
Tight junctions( occluding)- are like a zipper, compose of integral or “locking” proteins
Prevents passage of macromolecules, although some are leaky and doen provide a complete seal
Desmosomes- like a button, composer linker proteins in adjacent plasma membranes
distribute mechanical stress
can develop antibodies
Gap Junctions- small pores made or protein channels in adjacent plasma membranes
allows small substance to pass freely
4.2 Epithelial Tissue- found on every external and internal body surface, so acts as a barrier between the body and the environment
Covering/ lining epithelia
Glandular epithelia
5 Functions of Epithelial
Protection- continuous surface that shields underlying tissue from mechanical & thermal injury, produces keratin: undergoes mitosis rapidly & frequently.
Immune Defenses- cells of immune system scattered throughout epithelial tissues
Secretion- form glands that produce substances such as sweet, oil, and hormones
Transport into other tissues- selectively permeable barriers that allow certain substances to pass by passive or active transport
Sensation- most epithelial supplied with nerves that detect changes in internal & external environment, specialized epithelial. cells are responsible for some sensations
Components and classification of epithelia
Components (sides) of epithelia
have 1 side in contact with the extracellular space ( apical Surface), 1 in contact with deeper cells or the basal lamina (basal surface) and 2 sides
Classification of Epithelia: layers and shape
3 possible layers
Simple Epithelia- single layers of cells
Stratified epithelia- more than one layer of cells
Pseudostratified epithelia- single layer of cells that appears to be multilayered
3 possible shapes
Squamous Cells- flattened cells
Cuboidal Cells - short cells
Columnar Cells- tall and elongated cells
Combining layers and shapes
Simple epithelia layering- one cell layer,
no protection
lines hollow organs and surfaces where diffusion or transport occurs
includes:
simple squamous epithelia
single layer of flat cells
resemble fried eggs
diffuse occurs across cells
found in air sacs of lungs, serous membranes, and lining of blood
simple cuboidal
single layer of cube shaped cells
appear large with a central nucleus
diffusion occurs and some secret substances
found in kidney tubules and glands
Simple columnar epithelia
single layer of tall cells
appear rectangular
some have cilia
some produce secretion
found in the small intestine, uterine tube, kidney tubules and glands
pseudostratified columnar
single layer of of cells the appears stratified
most are ciliates
includes goblet cells that secrete mucus
found in respiratory passages and nasal cavities for protection
other type of layer/ shape combo is
Stratified epithelia layering-
thicker than simple epithelia
protective barriers
common in areas of high stress
cell shape changes throughout thickness of tissue
Types
Stratified Squamous Epithelial- Most widespread!
Keratinized- outer layer of skin
nonkeratinized
transitional epithelia (stretchy): cuboidal or Squamous?
others
stratified cuboidal epithelia( small amount
Stratified columnar epithelia (small amount)
Covering and lining epithelia
Stratified squamous epithelia
keratinized- outer layer of skin
nonkeratinized has distinct nucleated cells on apical surface
found in epithelium of the mouth, pharynx, esophagus, anud and vagina
Stratified cuboidal: has several layers of cuboidal epithelial cells and the underlying basal lamina; lines the ducts of certain exocrine glands (sweat glands)
Stratified columnar: Several layers of cuboidal epithelial cells and the underlying basal lamina; lines the ducts of certain exocrine glands (Salivary glands as well as part of the urethra and the conjunctive ( the thin, clear membrane lining the anterior surface of part of the eye and the inner eyelid)
• These are both rare in the human body
• Transitional Epithelium: The final part has several layers
of epithelial cells and the underlying basal lamina found in the organs of the urinary system; cells can change shape. It lines the interior kidney, the ureter the urinary bladder, and the urethra
Glandular Epithelia
A gland is a structure that makes and secretes a product
arise from epithelial tissue that grew inward into the underlying connective tissue rather than remaining at the surface
Secretory cells: manufacture a product and release it
classified by the number of cells, shapes, and how they release product
Glands releases its products in two ways
Exocrine Glands:(A gland that secretes a product through a duct to the external surface of the body or into the respiratory and gastrointestinal)
releases secretions to the apical surface of the epithelium generally to the exterior of the boyd and into a hollow organ that opens to the outside of the body
The secretions have local actions only- which means they only affect the cells in their general vicinity.
The simplest exocrine glands are the
Unicellular glands
The most common unicellular gland in the body is the Goblet cell:(Secretes mucus) found in the epithelium lining the digestive and respiratory tracts.
secrete mucus, a thick, sticky liquid that protects the underlying epithelium
Multicellular exocrine glands: made of clusters of secretory cells arranged in different ways.
Simple glands: have ducts that dont branch whereas compound glands do have branches
Arranged in three shapes
tubular: long and straight or coiled
Acinar: spherical
Tubuloacinar: both tubular and acinar portions
Types of exocrine secretion
Merocrine secretion: (within the wall) a type of secretion in which the product is secreted by exocytosis
Holocrine: ( outside the wall) a type of exocrine secretion in which the product accumulates in the cell until the cell ruptures and dies
accumulates in the cytosol, and the product isn't released until the cell ruptures and dies
Apocrine Secretion: rare: a portion of the cytoplasm is pinched off with the product being secreted
Endocrine Glands: Lack ducts that secrete their products which are usually hormones directly into the blood.
4.3 Connective Tissues
Connective tissues: a type of tissue characterized by extensive extracellular matrix
functions in support, protection, and transport
some more functions
connecting and binding: connect structures in the body
in organs they bind other tissues layers together
can be found between organs, they anchor them in place
Support: certain connective tissues such as bone and cartilage support the weight of the body
Protection: the bone tissue protects certain internal organs and the fat tissue provides shock absorption
Transport: blood is fluid connective tissue that is the main transport medium in the body
Two basic types of connective tissue:
Connective tissue proper: A type of connective tissue that generally functions to connect and support other tissues, widely distributed in the body, which connects tissues and organs
also called general connective tissue
widely distributed in the body
five cells of the connective tissue proper
Fibroblasts: a cell type within connective tissue proper that produces components of the extracellular matrix
they produce fibers as well as ground substance and other elements of the ECM
lie close to collagen fibers and they continuously produce collagen proteins
Adipocytes: also called fat cells, are another type of resident cell found in many different connective tissues, the main type of cells in the adipose tissue
found in the cytoplasm
nuclei are squished to the perimeter of the cell
Mast cells: are the largest resident cells in the connective tissues
cells of the immune system
have granules or cytosolic inclusions
Phagocytes: cells of the immune system that can ingest foreign substances, microorganisms, and dead and damaged cells by phagocytosis
two common types
Macrophages: which can be either resident or migrant cells in connective tissues
Neutrophils: migrant immune cells
Types of connective Tissue Proper
connective: also known as the areolar connective tissue,
contains a ground substance with protein fibers, fibroblasts,
jelly-like
found in the deep epithelium
supports and houses blood vessels and organs
most widespread throughout the body
Dense -3 types of tissue
Dense irregular Connective tissue
composed of protein fibers with mostly collagen fibers
arranged haphazardly
strong tissue that resists tension in all 3 planes
found in the dermis and around organs and joints
Dense Regular collagenous Connective Tissue
contains thick collagen fibers arranged in parallel bundles
resists tension in one direction
found in tendons ( which join muscle to the bone )and ligaments (which join bone to bone)
Dense Regular Elastic connective tissue
consists of mostly parallel elastic fibers with randomly oriented collagen fibers
allows organs to stretch
Found in the lining of the large blood vessels & some ligaments
Reticular Tissue
includes numerous reticular fibers produced by supporting fibroblasts
Form fine, mesh like networks for support & weblike nets that trap foreign cells; forms the basement membrane
Adipose tissue
fat tissue consisting of adipocytes, surrounding fibroblasts & ECM
can increase in size
functions insulation, warmth, shock absorption protection and energy reserve, found deep to skin in hypodermis
adipose tissue has two types White adipose and brown adipose
White Adipose: accumulates in the abdomen, breast , hip, buttocks and thighs, heart and abdominal organs
Brown adipose( we lose when wwe become adults), provide heat protectant like a tempostat
4.3 three specialized connective Tissues: cartilage, Bone, and Blood
Cartilage- 3 types Hyaline( most common, lines bones and joints) Fibrocartilage, Elastic( uncommon, ear, throat, and small intestine)
cartilages is tough, flexible tissue that absorbs shock, resistant to tension, compression and shearing forces
usually surrounded by outer sheath call perichondrium (made of dense irregular connective tissue, supplies nourishment from blood products to the cartilage
Cartilage is Avascular
Two cell types in cartilage
Chondroblasts- immature cartilage cells
Chondrocytes- mature cartilage cell, housed in cavities called Lacunae
Hyaline Cartilage
most common
ECM is ground substance with a fine collagen that forms small bundles;
Covers ends of bone , rib attachment sights to sternum and nose and respiratory tract
makes up most of the skeleton
Fibrocartilage
ECM is filled with bundles of collagen and some elastic fibers made from fibroblasts
found in fibrous joints, including the intervertebral discs and other articular discs that improve the fit of 2 bones
lacks a perichondrium
examples: labrum ( hips and shoulders)
Elastic Cartilage
ECM is filled with elastic fibers
found in the external ear (pinna)and parts if the larynx
Tissue vibration and assists in detection of sound in the air and production of sound in the larynx
Uncommon
Bone
Functions
suport
protection
attachment site for muscles
storage ( fat, calcium)
Houses bone marrow
Bone ECM consists of:
Organic portion
35% of bone mass is made of collagen fibers and osteo ground substance
Inorganic portion
655 of bone mass, made of calcium phosphate crystals( Hard)
Bone Cells
Osteoblasts- Immature,
Carry out bone deposition
synthesize organic portion and produce chemicals requires for calcium salts to deposit in the ECM
Osteocytes- Mature osteoblasts become this when surrounded by the ECM
immobile
live in lacune
produce substances for bone maintenance
Osteoclasts- multinucleated cells that carry out bone resorption ( break down of bone)
secrete hydrogen ions and enzymes to break down the ECM
Bone Remodeling- Bone deposition and bone resorption are constantly occurring in healthy bone, depending on type of stress placed
Blood- functions is transport, The bloods Ecm is plasma; contains water, dissolved solutes, and globular proteins
Cells of blood
Erythrocytes- RBC oxygen carriers
Leukocytes- WBC
Platelets- Blood clotting
4.4 Muscle Tissues
Muscle cells ( Myocytes)- excitable cells that respond to electrical or chemical stimulation
Cytoplasm is filled with proteins called Myofilaments, including the contractile proteins myosin and actin, surrounding the endomysium
Striated muscle cells - filaments are organized into regions that produce dark and light areas calle “band”s or striations
Smooth muscle cells - myofilaments are in irregular bundles scattered in the cytoplasm, NO STRIATIONS
Hypertrophy( increase) and atrophy (decrease)
Skeletal Muscles- attached to the skeleton to produce body movement
controlled by the nervous system
Voluntary movement
formed by fusion of embryonic myoblasts causes large multinucleate cells also called muscle fibers.
Cardiac Muscle- Only in the heart
involuntary contractions
short with branches and a single nucleus
intercalated disks
contains gap junction and tight junctions
found between cells and permit heart muscle to contract as a unit
Smooth muscle- found in walls of hollow organs, blood vessels, the eyes, skin , and ducts of some glands
involuntary
cells are flattened, single nucleus, gap junctions in the plasma membrane connect cells to other smooth muscle cells.
example: Gi tract
Nervous tissue- makes up majority if the brain, spinal cord, and nerves
ecm contains protein fibers, and mostly ground substance, wit unique proteoglycans
Two types of cells
Neuroglial Cell- supportive cells that anchor neurons and blood vessels in place, monitor the compression of the ECF, speed up the rate of nerve impulse transmission and circulate fluid around the brain and spinal cord
can divide by mitosis
Neurons - generate, conduct and receive nerve impulses
structure includes:
Cell body: large center with nucleus and organelles
Axon: moves impulse to target cell
Dendrites: arms that receive messages
Neurons are Amitotic ( you don't get new ones)
4.6 Putting it all together: the big picture of Tissues in organs
4.7 Membranes
membrane- thin sheet of one or more tissues that lines a body surface or cavity
consists of superficial layer of secretory cells and a layer of connective tissue
some have smooth muscle
anchors organs in place
serves as a barrier
function in immunity
secretes various substances
four general types of membranes
2 true membranes
serous
synovial
2 “membrane- like “ structures
mucous
cutaneous
True membranes- fit the structural and functional definitions of a membrane
DO NOT open outside of the body
Serous membrane- line the pleural, pericardial, and peritoneal body cavities
consists of simple squamous epithelial tissue called mesothelium
outer lays is visceral layer
mesothelial cells produce Serous fluid which lubricates organs
Synovial Membranes- line cavities surrounding freely moveable joints, including the hip, knee, elbow, and shoulder
made of two connective tissue layers
inner- consists of modified fibroblasts called synoviocytes- secret synovial fluid that lubricates the joints
External— a mixture of loose and dense irregular connective tissue
Membrane-Like Structures- don’t completely fit the structural and functional definitions of a membrane: DO OPEN to the outside of the body
Mucous membranes- lines the body passages as part of walls of hollow organs that open to the outside of the body
consists of a epithelium, basement membrane, and a layer oif connective tissue called lamina prpria and sometimes smooth muscle
glands with goblet cells that secrete mucus
Cutaneous membrane - the skin, which is the largest organ
open to the environment
4.8 Tissue repair
process of wound healing, occurs differently in different tissue & is dependant on tissue ability to regenerate
2 possible process of healing
Regeneration- damage or dead cells are replaced with cells of the same type
this is a good thing
Fibrosis- fibroblasts divide by mitosis and produce Collagen to fill in defect left by injury
results in scar tissue, which is dense irregular connective tissue
not good or strong
Capacity of specific tissues for tissue repair
Regeneration- or fibrosis occurring in tissue largely determined by ability of tissue to undergo mitosis
Tissue types and their mode of healing
Epithelial tissues-
undergo regeneration
many contain immature stem cells; divide continually to replace dead, injured, or worn-out cells
Connective Tissue
most heal by regeneration
cartilage is an exception and often heals by FIBROSIS
Smooth muscle Tissue-
Usually regeneration
cells retain their ability to undergo mitosis
Cardiac and Skeletal Muscle
generally heal by Fibrosis
cardiac and skeletal muscle cell size and complexity prevent mitosis
satellite cell in skeletal muscle tissue can divide and become skeletal muscle cells which provides a limited degree of regeneration
Neurons of nervous Tissue
Do not regenerate
Other factors of tissue repair
nutrition and blood supply- important determines of tissues repair
nutrition- collagen is needed in tissue repair, so protein intake and vitamin c (needed soe fibroblasts to make collagen) must be considered
Blood supply- adequate blood flow to injured areas is also important
people suffering from disease of the blood vessels may have non healing wounds, even in tissues capable of regeneration