A&P Chapter 4: Tissues

what are tissues?

a group of similar cells that perform a common/related function

how many primary tissues types are there? name them.

1. epithelial

2. connective

3. nervous

4. muscle

what is epithelium/epithelial tissue?

a sheet of cells covering body surface or lining a body cavity

what are the 2 types of epithelia?

1. surface epithelia

2. glandular epithelia

what is surface epithelia? where is it found

tightly packed sheets of cells that covers external surface of the body and lines body cavities/organs

found in:

• outer skin layer

• inner lining of digestive/respiratory tracts

• lining of blood and lymph vessels

• lining of serous cavities (pleural, peritoneal, pericardial)

what is glandular epithelia?

it forms secretory units of glands

• endocrine: secretes internally (ex: hormones)

• exocrine: secretes externally (ex: sweat)

what are the functions of epithelia? give examples of where the function happens

FEAPS

1. filtration: kidneys (separates good from bad)

2. excretion: intestines, kidneys (pushed bad stuff into urine)

3. absorption: intestines, kidneys (gets good stuff into the blood)

4. protection: skin

5. secretion: kidneys, glands(ex: sweat)

what are the characteristics of epithelia?

1. high cellularity

2. tight junctions and desmosomes

3. polarity

4. supported by connective tissue

5. avascular but innervated

6. regenerative

explain high cellularity in epithelia

its mostly tight-packed cells

little ECM

explain tight junctions and desmosomes in epithelia

tight junctions: chemical barrier between cells

desmosomes: strong chemical reactions

they’re lateral contacts between adjacent cells

foam sheets turn into the barrier

explain polarity in epithelia

apical surface: faces body exterior or organ cavity/lumen

basolateral surface: faces tissue (interior)

explain connective tissue support in epithelia

basment membrane hold everything together

• made up of basal lamina and reticular lamina

what does a vascular but innervated mean in epithelia?

avascular: no blood vessels, gets oxygen and nutrients from CT layer

innervated: has nerve ending so it has sensations

explain regeneration in epithelia

they rapidly replace lost cells by cell division

how can we classify epithelia?

1. number of layers

   1. simple

   2. stratified

2. cell shape

   1. squamous

   2. cuboidal

   3. columnar

describe the features, function, and location of simple squamous epithelium

features: single layer of flattened cells, disc-shaped nuclei

• special feature: endothelium: lines blood and lymphatic vessels and inside of heart

function: allows materials to pass by diffusion and filtration

location: air sacs of lungs, blood and lymphatic vessels

describe the features, function, and location of simple cuboidal epithelium

features: single layer of cube-like cells, large circular nuclei

function: secretion and absorption (like a sponge)

location: kidney tubules (to reabsorb nutrients into blood)

describe the features, function, and location of simple columnar epithelium

features: single layer of tall cells, oval nuclei, can have micro-villi and cilia

function: absorption, mucus secretion, can produce a subset of goblet cells

location: non ciliated in the gi tract, gallbladder, uterine tubes

describe the features, function, and location of stratified squamous epithelium

features: thick layers over squamous cells

function: protects against abrasion

location: lines the esophagus, mouth, v*gina

describe the features, function, and location of statified cuboidal epithelium

features: many layers of cuboidal cells

function: protection

location: ducts of sweat glands

describe the features, function, and location of stratified columnar epithelium

features: many layers of columnar cells

function: protection

location: salivary glands

describe the features, function, and location of pseudostratified columnar epithelium

features: technically one layer of cells (they all touch the basement membrane), can have cilia

function: secretion of mucus, cilia moves it along the path

location: lines the upper respiratory tract and trachea

describe the features, function, and location of transitional epithelium

features: all types of tissues mushed tg

function: stretches and distends urinary organ

location: lines bladder, ureter, parts of urethra

what is glandular epithelia?

one or more cells that makes and exports a product (secretion)

how many types of glandular epithelia are there?

2 types:

1. endocrine glands - secretes internally, ductless, product is hormones

2. exocrine glands - secretes externally onto body surfaces/body cavities (ex, sweat, oil, saliva)

   1. can be unicellular or multicellular

      1. uni: has goblet cell that releases protein

      2. multi: has secretory unit and duct that acts as the passageway

what are the modes of secretion of multicellular glands?

1. merocrine: exocytosis

2. holocrine: whole cell detaches, disintegrates, and releases contents

3. apocrine: partial breakoff from cell (released from disintegrated part of cell)

what are the main types of connective tissue?

1. CT proper (includes fats and ligaments)

2. cartilage

3. bone

4. blood

what are the major functions of CT? give some examples

1. binding and support

2. protection (ex: nose cartilage)

3. insulation (ex: adipose tissue)

4. transportation

what is the most common characteristic of CT? give an example that contains this characteristic

its mostly extracellular material/matrix (ECM) with few cells

• ex: bone is made up of mostly proteins and mineral deposits with cells imbedded within the tissue

what are the structural elements of CT? briefly explain them

1. ground substance: material that fills the space between cells

2. fibers: provides support for CT

3. cells: includes immature/undifferentiated AND mature/quiescent cells

what is ground substance of CT made of and whats its function?

made of:

• extracellular fluid (ECF) with mostly H2O

• proteoglycans: proteins with long sugar chains attached that retains/absorbs water in the area

function:

• is like an extracellular gel and hold large amounts of fluid

• allows for diffusion of nutrients from capillaries to tissue cells

what are the different types of fibers in CT? explain their features/functions

1. collagen: tough, high tensile strength (rope-like) to ECM

2. elastic fibers: long/thin, forms a network that allows for recoil of stretched CT

3. reticular fibers: short/fine, forms delicate network where CT connects to other tissue, makes a nice bedding

what are the names of immature/undifferentiated and mature/quiescent CT cells?

CT proper:

• immature: fibroblast

• mature: fibrocyte

cartilage:

• immature: chondroblast

• mature: chondrocyte

bone:

• immature: osteoblast

• mature: osteocyte

blood:

• immature: hematopoietic stem cell

• mature: red blood cells, white blood cells, megakaryocytes (produces platelets)

what are the additional cell types in CT? briefly explain them

1. adipocytes (fat cells): energy storage, insulation

2. white blood cells: fights infections

3. macrophages: type of WBC, eats foreign substances (phagocytosis)

4. mast cells: inflammatory response, releases histamine (chemical messenger released to cells)

how is connective tissue identified?

1. loose

2. dense

what are the different types of loose CT? describe features/location

1. loose areolar CT

   1. made of mostly collagen and some elastic fibers, widely spaced, loose packing material

2. loose reticular CT

   1. loose network of reticular fibers

   2. forms “bed” to support cells in lymph nodes, spleen, and bone marrow

what are the different types of dense CT?

1. dense regular CT

   1. parallel collagen fibers, few elastic fibers, high tensile strength, elongated/squished nuclei

   2. located in tendons (b → m), aponeuroses (m → m), ligaments (b → b), fascia

2. dense irregular CT

   1. irregularly arranged collagen fibers, some elastic fibers, able to withstand tension from multiple directions

   2. found in dermis, digestive tract walls

what is an additional CT proper tissue type?

adipose tissue:

• very little matrix

• tightly packed

• located under skin, around kidney and eyeballs, within breasts

what are the different types of cartilage?

1. hyaline

2. elastic

3. fibrocartilage

describe functions/locations of hyaline cartilage

• firm, matrix lacks form, contains collagen

• supports, reinforces, cushions, and resists compression

• forms embryotic (fetus) skeleton and cartilage structure of nose, trachea, larynx

describe functions/locations of elastic cartilage

• similar to hyaline, but more elastic fibers

• maintains shape of structures, allows flexibility

• located in external ear and epiglottis

describe functions/locations of fibrocartilage

• similar to hyaline, but less firm

• mostly collagen

• good tensile strength, absorbs compressive shock

• located in intervertebral discs, discs of knee joint

describe features/functions of bone/osteons

• matrix of many collagen fibers and calcium deposits

• supports and protects body

• stores calcium and other minerals

describe features/functions of blood

• RBC, WBC, and platelets in fluid plasma

• transports gases, nutrients, wastes, and substances

• contained within blood vessels

what are the different types of nervous tissue? explain them.

1. neurons: branching cells that generate and conduct impulses (elec. and chem.), responds to stimuli, rapid communication

2. glial cells: nonconducting cells that insulate and protect neurons, creates a “good environment”

explain the common features and different types of muscular tissue

• highly cellular and vascularized

• cells have myofilaments (actin and myosin proteins)

• can contract

• 3 types: skeletal, cardiac, smooth

describe functions/locations of skeletal muscle

• long, cylindrical, multinucleated cells

• has striations bc of actin and myosin

• enclosed in CT sheath

• voluntary control

• found between bones

describe functions/locations of cardiac muscle

• branched, uninucleate cells, interconnected by intercalated discs

• has striations bc of actin and myosin

• only found in heart wall, contracts to pump blood

• involuntary control

describe functions/locations of smooth muscle

• spindle-shaped, uninucleated cells

• contracts/relaxes to push substances thru

• found in walls of hollow organs except heart

• involuntary control

what are the different types of covering/layers by tissue membranes?

1. cutaneous membrane (skin)

2. mucous membrane (mucosae)

3. serous membrane (serosae)

describe the features/locations of the cutaneous membrane covering/layer

is the skin

2 parts:

• stratified squamous epithelium (epidermis)

• thick layer of irregular CT (dermis)

~ 30 layers

describe the features/locations of the mucous membrane covering/layer

• lines body cavities “open to the exterior” (exposed to external air, food, substances)

• epithelium is attached to the basement membrane and lamina propria (loose CT)

• located in respiratory, digestive, and urogenital tracts

• moist with mucus (or w urine in the urogenital tract)

describe the features/locations of the serous membrane covering/layer

• lines “closed” ventral body cavities (no exposure to external substances)

• simple squamous epithelium attached to thin layer of loose areolar CT

• epithelial cells secrete hyaluronic acid fluid for lubrication

• located in pleural, pericardial, peritoneal, and abdominopelvic cavities

what are the different types of tissue repair? explain them.

1. regeneration: replace damaged tissue with the same tissue

2. fibrosis: replace damaged tissue with fibrous CT (scar tissue)

which muscle cannot regenerate? why?

cardiac muscles do NOT regenerate, they are replaced with fibrose. But, the heart won’t work as well because fibrose makes it tougher which causes it to be harder to contract/

what are the steps of tissue repair? explain them.

1. inflammation

   1. injured tissue cells, mast cells, and macrophages release inflammatory chemicals (ex: histamine)

   2. dilates nearby blood vessels

   3. blood plasma, clotting proteins, and antibodies leak into injured tissue

   4. blood clot forms

   5. turns into a scab as it dries

   6. macrophages phagocytose and digest debris

2. organization

   1. fibroblasts migrate into wound and deposit new collagen fibers

   2. blood clot replaces by granulation tissue (new temporary CT, network of blood vessels that forms on the surface of a wound)

3. regeneration/fibrosis

   1. epithelial cells multiply and migrate to fill in wound under scab

   2. granulation tissue remodeled but remains as a fibrous scab