Ingegneria delle tecnologie per la salute Fondamenti di ...Fondamenti di anatomia e istologia aa....

Ingegneria delle tecnologie per la salute

Fondamenti di anatomia e istologia

aa. 2018-19

LEZIONE 3 ISTOLOGIA ed EMBRIOLOGIA

Anatomia umana Edizione italiana a cura di Fabrizio Michetti MCKINLEY - O'LOUGHLIN Data di pubblicazione: maggio 2014 Prezzo: 49,50 € ISBN: 978-88-299-2655-8 Codice Piccin: 1312165 Libro in italiano

Atlante di anatomia Edizione italiana a cura di Elena Donetti KAMINA Data di pubblicazione: settembre 2014 Prezzo: 45,00 € ISBN: 978-88-299-2668-8 Codice Piccin: 1100850 Libro in italiano

Colorare l'anatomia Edizione italiana a cura di Raffaele De Caro e Sergio Galli KAPIT - ELTON Data di pubblicazione: marzo 2016 Prezzo: 20,00 € ISBN: 978-88-299-2747-0 Codice Piccin: 1101200 Libro in italiano

Lezione 3. Cenni di embriologia ed istologia generale.

https://human.biodigital.com/index.html

https://www.openstaxcollege.org/files/textbook_version/hi_res_pdf/13/col11496-1.7_20150715-OP.pdf

https://lectureug5.files.wordpress.com/2014/02/difiores-atlas-of-histology-with-functional-correlations-11th-ed.pdf

THE TISSUE LEVEL OF ORGANIZATION

After studying this chapter, you will be able to: • Identify the main tissue types and discuss their roles in the human body • Identify the four types of tissue membranes and the characteristics of each that make them functional • Explain the functions of various epithelial tissues and how their forms enable their functions • Explain the functions of various connective tissues and how their forms enable their functions • Describe the characteristics of muscle tissue and how these enable function • Discuss the characteristics of nervous tissue and how these enable information processing and control of muscular and glandular activities

our body: at least 200 distinct cell types.

same internal structures but vary enormously

in shape and function.

occur in organized layers: tissue

starts as a single cell at fertilization and it

gives rise to trillions of cells, each built from

the same blueprint, but organizing into tissues

and becoming irreversibly committed to a

developmental pathway.

Tissue = a group of cells found

together in the body, that share a

common and morphological features

and are arranged in an orderly pattern

that achieves the tissue’s functions.

many types of cells but organized into

4 broad categories of tissues:

1. epithelial,

2. connective,

3. muscle

4. nervous

with a specific functions that

contribute to the overall health and

maintenance of the body.

Histology = microscopic study of

tissue appearance, organization, and function.

Types of Tissues

Histology is a visual, as well as a

very colorful, science that is

studied with the aid of a light micro

scope. The prepared specimens for

examination are thinly sliced,

placed on a glass slide, stained

with a variety of stains, and

examined with a light microscope

via a light beam that passes

through the tissues that are fixed

on the slide.

Tissue Preparation—Light Microscopy

Antonie van Leeuwenhoek (1632–1724) is credited with bringing the microscope to the attention of biologists

FIXATION

= prompt immersion of the specimen with

different chemical solutions, to preserve a

section of tissue or organ for histologic

examination

essential in order to permanently

preserve structural and molecular

composition of specimen.

to further accelerate penetration and

proper fixation process, tissue

specimen is first cut into small pieces

and then immersed into fixative.

hardens specimen for sectioning,

causes cross-linkage of

macromolecules within the cells,

reduces cellular degeneration,

preserves integrity of cells and tissues,

and increases their affinity to take up

different stains.

most commonly used fixative for light

microcopy is neutral-buffered

FORMALDEHYDE.


Aldehyde fixatives form crosslinks between proteins.

POSTFIXATION

After fixation, water must first be removed by

passing it through a series of ascending ALCOHOL

(ethanol) concentrations, usually from 70 to 100%

then specimen must be cleared of alcohol by

passing it through several changes of such clearing

agents as XYLENE

Once the specimen is impregnated with the clearing

agent xylene, it is then placed in a warm mold

containing melted PARAFFIN. Once removed from

the heat source, the paraffin in the mold cools,

solidifies, and encases the specimen.

paraffin block then trimmed to the size of the

specimen and mounted in an instrument called a

MICROTOME [precisely advances the paraffin block

so that the sections are cut at specific and

predetermined increments with a steel knife] =

sections are normally cut at 3-10 μm thickness.

thin paraffin sections are then collected and floated

in a warm water bath and placed onto a glass slide

that has been covered with a thin layer of albumen,

which serves as an adhesive medium for the

specimen.


paraffin sections on the glass slide

are colorless needs to be

stained.

paraffin must first be dissolved

from the specimen with solvents,

such as xylene, and the sections

rehydrated with a series of

decreasing alcohol concentrations.

hydrated sections can then be

stained with a variety of water-

soluble stains, which selectively

stain various components of the

specimen

Most of the stains used for

histologic slide preparations act

like acidic or basic compounds:

structures that stain most readily

with basic stains are called

BASOPHILIC, and those that stain

with acidic stains are called

ACIDOPHILIC [most common

stains are hematoxylin and eosin

stains]

Staining of Sections

Staining of Sections

Interpretation of Histologic Sections

the most challenging and difficult aspects of histology: interpretation of what the 2-dimensional histology sections represent in 3 dimensions.

Histologic sections = thin, flat slices of fixed and stained tissues or organs mounted on flat glass slides.

sections normally composed of cellular, fibrous, and tubular structures cut in different planes variety of shapes, sizes, and layers may be visible, depending on the plane of section.

Fibrous structures are solid and are found in connective, nervous, and muscle tissues.

Tubular structures are hollow and represent various types of blood vessels, lymph vessels, glandular ducts, and glands of the body.

Planes of Section of a Round, Solid Object

Planes of Section Through a Hollow Structure or a Tube

Transmission and Scanning Electron Microscopy

Cell microscopic anatomy (TEM)

Ciliated and nonciliated cells

Junctional complex

Basal region

Basal region in ions transporting cell

Cilia and microvilli

Nuclear envelope and pores

Mitochondria

Golgi apparatus

Lysosomes

Mitosis

The 4 Types of Tissues

1. Epithelial tissue (epithelium) = sheets of cells that cover exterior surfaces of the body, internal cavities and passageways, and forms certain glands.

2. Connective tissue = binds cells and organs together (functions in the protection, support, and integration of all parts of the body)

3. Muscle tissue = excitable, responding to stimulation and contracting to provide movement, and occurs as 3 major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart.

4. Nervous tissue = also excitable, allowing the propagation of electrochemical signals in the form of nerve impulses .

The 4 Types of Tissues

Organs are made of many different tissues…of the 4 fundamental types

sections through 4 different organs: Intestines, Skin, Lung, & Trachea. (each organ is made of multiple tissues and that their are variations on how the tissues are designed)

Embryonic Origin of Tissues

totipotent

three major cell lineages established within the embryo


3 lineages of embryonic cells forms 3 distinct germ layers identified by its relative position: 1. ectoderm (ecto-= “outer”), 2. mesoderm (meso- = “middle”), 3. endoderm (endo- = “inner”).


!!! epithelial tissue originates in all three layers, whereas nervous tissue derives primarily from the ectoderm and muscle tissue from mesoderm.

Tissue membrane = thin layer or sheet of

cells that covers the outside of the body (for

example, skin), the organs (for example,

pericardium), internal passageways that lead

to the exterior of the body (for example,

abdominal mesenteries), and the lining of the moveable joint cavities.

Tissue Membranes

2 basic types

1. connective tissue 2. epithelial membranes

Tissue Membranes

1. Connective Tissue Membranes = formed solely from connective

tissue, encapsulate organs, and line our movable joints (synovial

membrane)

2. Epithelial Membranes = composed of epithelium attached to a

layer of connective tissue

i. mucous membrane (mucosae) = line the body cavities and hollow

passageways that open to the external environment, and include the

digestive, respiratory, excretory, and reproductive tracts. Mucous,

produced by the epithelial exocrine glands, covers the epithelial layer.

The underlying connective tissue, called the lamina propria, supports

the epithelial layer.

ii. serous membrane = composed of mesodermally derived epithelium

called the mesothelium that is supported by connective tissue, line

coelomic cavities (do not open to outside).

iii. cutaneous membrane (skin) = stratified squamous epithelial membrane resting on top of connective tissue.

Epithelial Tissue

share structural/ functional features: highly cellular, with little or no extracellular

matrix between cells cell junction = specialized intercellular

connection between cell polarity = differences in structure and function

between the exposed or apical facing surface of the cell and the basal surface

basal lamina = (a mixture of glycoproteins and collagen) provides an attachment site for the epithelium, separating it from underlying connective tissue and attaches to a reticular lamina, which is secreted by the underlying connective tissue, forming a basement membrane that hold it all together.

nearly completely avascular. capable of rapidly replacing damaged and dead

cells.

= essentially large sheets of cells covering all the surfaces of the body exposed to the outside world + lining the outside of organs + much of the glandular tissue of the body;

Epithelial Tissue

Generalized Functions of Epithelial Tissue • provide the body’s first line of protection from physical, chemical, and biological wear and

tear, controlling permeability and allowing selective transfer of materials across a physical barrier

• are sometimes capable of secretion and release mucous and specific chemical compounds onto their apical surfaces.

The Epithelial Cell typically characterized by the polarized distribution of organelles and membrane-bound proteins between their basal and apical surfaces: certain organelles are segregated to the basal sides, whereas other organelles and extensions, such as cilia (microscopic extensions of the apical cell membrane that are supported by microtubules), when present, are on the apical surface and beat in unison and move fluids as well as trapped particles.

Epithelial Tissue

Cell to Cell Junctions Cells of epithelia are closely

connected and are not

separated by extracellular

material. 3 basic types of

connections allow varying

degrees of interaction between

the cells:

1. tight junctions,

2. anchoring junctions, 3. gap junctions

Epithelial Tissue

Classification of Epithelial Tissues

classified according to the shape

of the cells and number of the cell

layers formed. Transitional

describes a form of specialized

stratified epithelium in which the shape of the cells can vary.

Epithelial Tissue

Classification of Epithelial Tissues

classified according to the shape of the cells and number of the cell layers

formed. Transitional describes a form of specialized stratified epithelium in which the shape of the cells can vary.

Epithelial Tissue

Both simple and pseudostratified columnar epithelia

are heterogeneous epithelia because they include

additional types of cells interspersed among the

epithelial cells. For example, a goblet cell is a mucous-secreting

unicellular “gland” interspersed between the columnar epithelial cells of mucous membranes

goblet cell

Epithelial Tissue

different categories of epithelial cell tissue cells

Epithelial Tissue

Glandular Epithelium gland = a structure made up of one or more cells modified to synthesize and secrete chemical substances; most glands consist of groups of epithelial cells. 1. Endocrine Glands a ductless gland that releases secretions (hormones) directly into surrounding tissues and fluids (endo- = “inside”), that are part of regulatory system 2. Exocrine Glands gland whose secretions leave through a duct that opens directly, or indirectly, to the external environment (exo- = “outside”). through a tubular duct that leads to the epithelial surface

Epithelial Tissue

Exocrin Glandular Structure Exocrine glands classified: • unicellular = scattered

single cells (goblet cells)

• multicellular (classified by

structure)

Epithelial Tissue

Exocrin Glandular Methods and Types of Secretion Exocrine glands classified

• mode of secretion

• nature of the substances released

serous gland watery, blood-plasma-like secretions mucous gland watery to viscous products rich in the glycoprotein mucin. mixed glands both serous and mucous glands and release both types of secretions.

Epithelial Tissue

Sebaceous Glands secrete oils that lubricate and protect the skin and

are holocrine glands (are destroyed after releasing their contents, new glandular cells form to replace the cells that are lost).

Epithelial Tissue

Type of Tissue Function Location

Pseudostratified columnar removing dust and particles from airways, has cilia

lines the respiratory passageways

https://biologycorner.com/anatomy/histology/hist1.GIF

Epithelial Tissue

Simple Columnar Absorption lines the uterus and most organs of the digestive tract



Epithelial Tissue

Simple Cuboidal Secretion and Absorption glands, kidney tubules, ovaries

https://biologycorner.com/anatomy/histology/hist3.gif

https://biologycorner.com/anatomy/histology/hist3.gif

Epithelial Tissue

Simple Squamous Diffusion and Filtration lungs, walls of capillaries and vessels



Epithelial Tissue

Stratified Squamous Protects underlying cells Skin (keratinized) and the throat, vagina, mouth (soft)




https://biologycorner.com/anatomy/histology/keratin.gif

Epithelial Tissue

Stratified Cuboidal Protection lines ducts of the mammary glands, sweat glands, pancreas

https://biologycorner.com/anatomy/histology/hist17.jpg



Epithelial Tissue

Stratified Columnar Protection, secretion male urethra and vas deferens, parts of the pharynx




Epithelial Tissue

Transitional (unstretched) Specialized to become distended urinary tract






https://biologycorner.com/anatomy/histology/transit.gif

Connective Tissue

General structure of CT

cells are dispersed in a matrix

matrix = a large amount of extracellular

material produced by the CT cells and plays a

major role in the functioning

matrix component = ground substance often

crisscrossed by protein fibers

ground substance usually fluid, but it can also

be mineralized and solid (bones)

CTs = vast variety of forms, but typically 3

characteristic components: cells, large

amounts of amorphous ground substance,

and protein fibers.

Connective Tissue

In connective tissue, the ground substance is an amorphous gel-like substance surrounding the cells. In a tissue, cells are surrounded and supported by an extracellular matrix. Ground substance traditionally does not include fibers (collagen and elastic fibers), but does include all the other components of the extracellular matrix. The components of the ground substance vary depending on the tissue. Ground substance is primarily composed of water, glycosaminoglycans (most notably hyaluronan), proteoglycans, and glycoproteins. Usually it is not visible on slides, because it is lost during the preparation process.

GROUND SUBSTANCE

https://en.wikipedia.org/wiki/Connective_tissue

https://en.wikipedia.org/wiki/Extracellular_matrix

https://en.wikipedia.org/wiki/Collagen

https://en.wikipedia.org/wiki/Elastic_fiber

https://en.wikipedia.org/wiki/Glycosaminoglycans

https://en.wikipedia.org/wiki/Hyaluronan

https://en.wikipedia.org/wiki/Proteoglycans

https://en.wikipedia.org/wiki/Glycoproteins

Connective Tissue

Functions of Connective Tissues Support and connect other tissues Protection (fibrous capsules and bones that protect delicate organs and, of course, the

skeletal system). Transport of fluid, nutrients, waste, and chemical messengers is ensured by specialized

fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal

insulation of the body.

Embryonic Connective Tissue All connective tissues derive from the mesodermal layer of the embryo. The first connective tissue to develop in the embryo is mesenchyme, the stem cell line from which all connective tissues are later derived. Clusters of mesenchymal cells are scattered throughout adult tissue and supply the cells needed for replacement and repair after a connective tissue injury. A second type of embryonic connective tissue forms in the umbilical cord, called mucous connective tissue or Wharton’s jelly. This tissue is no longer present after birth, leaving only scattered mesenchymal cells throughout the body.

Connective Tissue

Classification of CTs 3 broad categories of CT are classified according to the characteristics of their ground substance and the types of fibers found within the matrix

Connective Tissue

Connective Tissue Proper CELLS Fibroblasts present in all CT proper Fibrocytes, adipocytes, and mesenchymal cells are fixed cells (remain

within the connective tissue). Other cells move in and out in response to chemical signals: macrophages,

mast cells, lymphocytes, plasma cells, and phagocytic cells (actually part of the immune system)

Connective Tissue

Connective Tissue Proper Connective Tissue Fibers and Ground Substance (all secreted by fibroblasts)

3 main types : • Collagen fiber = made from fibrous protein subunits linked together to form a

long and straight fiber, while flexible, have great tensile strength, resist stretching, and give ligaments and tendons their characteristic resilience and strength.

• Elastic fiber = protein elastin (that after being stretched or compressed, it will return to its original shape) along with lesser amounts of other proteins and glycoproteins.

• Reticular fiber = also formed from the same protein subunits as collagen fibers, but arrayed in a branching network.

• All of these fibers embedded in ground substance = made of polysaccharides, specifically hyaluronic acid, and proteins (combined to form a proteoglycan with a protein core and polysaccharide branches). The proteoglycan attracts and traps available moisture forming a clear, viscous, colorless matrix.

Connective Tissue

Connective Tissue Proper Loose Connective Tissue found between many organs where it acts both to absorb shock and bind tissues togethe + allows water, salts, and various nutrients to diffuse through to adjacent or imbedded cells and tissues. 1. Adipose tissue = mostly of fat storage cells, with little extracellular matrix. White fat contributes mostly to lipid storage and can serve as insulation from cold temperatures and mechanical injuries. Brown adipose tissue is more common in infants (“baby fat”) and is thermogenic

Connective Tissue

Connective Tissue Proper Loose Connective Tissue 2. Areolar tissue shows little specialization and fills the spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs in the abdominal cavity. Areolar tissue underlies most epithelia and represents the connective tissue component of epithelial membranes. 3. Reticular tissue = mesh-like, supportive framework for soft organs such as lymphatic tissue, spleen, and liver.

Connective Tissue

Supportive Connective Tissues allow the body to maintain its posture and protect internal organs + 2 major forms:

1. Cartilage The distinctive appearance of cartilage is due to polysaccharides called chondroitin sulfates, which bind with ground substance proteins to form proteoglycans. Embedded within the cartilage matrix are chondrocytes and the space they occupy are called lacunae (singular = lacuna). A layer of dense irregular connective tissue, the perichondrium, encapsulates the cartilage. avascular very slow healing. 3 main types:

2. Bone the hardest CT with rigid extracellular matrix contains mostly collagen fibers embedded in a mineralized ground substance containing hydroxyapatite. Osteocytes are located within lacunae. highly vascularized tissue.

Connective Tissue

Fluid Connective Tissue = blood and lymph where cells circulate in a liquid extracellular matrix

Connective Tissue

The following types of connective tissue are covered in this activity:

1. Loose (areolar) connective tissue (delicate thin layers between

tissues; present in all mucous membranes)

2. Adipose tissue (fat)

3. Dense connective tissue (tendons/ligaments)

4. Hyaline cartilage (nose/ends of long bones/ribs)

5. Elastic cartilage (outer ear/epiglottis)

6. Fibrocartilage (between vertebrae/knee joints/pubic joint)

7. Bone (skeletal system)

8 Blood (bloodstream)

Table 4.1 Comparison of Classes of Connective Tissues (1 of 2)

Connective Tissue

Connective Tissue

Table 4.1 Comparison of Classes of Connective Tissues (2 of 2)

Copyright © 2010 Pearson Education, Inc.

Figure 4.8a Connective tissues.

(a) Connective tissue proper: loose connective tissue, areolar

Description: Gel-like matrix with all three fiber types; cells: fibroblasts, macrophages, mast cells, and some white blood cells.

Function: Wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid.

Location: Widely distributed under epithelia of body, e.g., forms lamina propria of mucous membranes; packages organs; surrounds capillaries.

Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (300x).

Epithelium

Lamina propria

Fibroblast nuclei

Elastic fibers

Collagen fibers


Figure 4.7 Areolar connective tissue: A prototype (model) connective tissue.

Macrophage

Fibroblast

Lymphocyte

Fat cell

Mast cell

Neutrophil

Capillary

Cell types Extracellular

matrix

Fibers

• Collagen fiber • Elastic fiber • Reticular fiber

Ground substance


Figure 4.8b Connective tissues.

(b) Connective tissue proper: loose connective tissue, adipose

Description: Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, 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 the hypodermis; around kidneys and eyeballs; within abdomen; in breasts.

Photomicrograph: Adipose tissue from the subcutaneous layer under the skin (350x).

Nucleus of fat cell

Vacuole containing fat droplet

Adipose tissue

Mammary glands


Figure 4.8c Connective tissues.

(c) Connective tissue proper: loose connective tissue, reticular

Description: Network of reticular fibers in a typical loose ground substance; reticular cells lie on the network.

Function: Fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.

Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).

Photomicrograph: Dark-staining network of reticular connective tissue fibers forming the internal skeleton of the spleen (350x).

Spleen

White blood cell (lymphocyte)

Reticular

fibers


Figure 4.8d Connective tissues.

(d) Connective tissue proper: dense connective tissue, dense regular

Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast.

Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction.

Location: Tendons, most ligaments, aponeuroses.

Photomicrograph: Dense regular connective tissue from a tendon (500x).

Shoulder joint

Ligament

Tendon

Collagen fibers

Nuclei of fibroblasts


Figure 4.8e Connective tissues.

(e) Connective tissue proper: dense connective tissue, dense irregular

Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast.

Function: Able to withstand tension exerted in many directions; provides structural strength.

Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of digestive tract.

Photomicrograph: Dense irregular connective tissue from the dermis of the skin (400x).

Collagen

fibers

Nuclei of

fibroblasts

Fibrous

joint

capsule


Figure 4.8f Connective tissues.

(f) Connective tissue proper: dense connective tissue, elastic

Description: Dense regular connective tissue containing a high proportion of elastic fibers.

Function: Allows recoil of tissue following stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration.

Location: Walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tubes.

Elastic fibers

Aorta

Heart Photomicrograph: Elastic connective tissue in

the wall of the aorta (250x).


Figure 4.8g Connective tissues.

(g) Cartilage: hyaline

Description: Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) lie in lacunae.

Function: Supports and reinforces; has resilient cushioning properties; 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.

Photomicrograph: Hyaline cartilage from the

trachea (750x).

Costal cartilages

Chondrocyte in lacuna

Matrix


Figure 4.8h Connective tissues.

(h) Cartilage: elastic

Description: Similar to hyaline

cartilage, but more elastic fibers

in matrix.

Function: Maintains the shape

of a structure while allowing

great flexibility.

Location: Supports the external

ear (pinna); epiglottis.

Photomicrograph: Elastic cartilage from

the human ear pinna; forms the flexible

skeleton of the ear (800x).

Chondrocyte

in lacuna

Matrix


Figure 4.8i Connective tissues.

(i) Cartilage: fibrocartilage

Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate.

Function: Tensile strength with the ability to absorb compressive shock.

Location: Intervertebral discs; pubic symphysis; discs of knee joint.

Photomicrograph: Fibrocartilage of an

intervertebral disc (125x). Special staining

produced the blue color seen.

Intervertebral

discs

Chondrocytes

in lacunae

Collagen

fiber


Figure 4.8j Connective tissues.

(j) Others: bone (osseous tissue)

Description: Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized.

Function: Bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis).

Location: Bones

Photomicrograph: Cross-sectional view of bone (125x).

Lacunae

Lamella

Central canal


Figure 4.8k Connective tissues.

(k) Others: blood

Description: Red and white

blood cells in a fluid matrix

(plasma).

Function: Transport of

respiratory gases, nutrients,

wastes, and other substances.

Location: Contained within

blood vessels.

Photomicrograph: Smear of human blood (1860x); two

white blood cells (neutrophil in upper left and lymphocyte

in lower right) are seen surrounded by red blood cells.

Neutrophil

Red blood cells

Lymphocyte

Plasma

EXAMPLES

Can you name?

First, the tissue type

Second, where in the body the tissue is found

Connective Tissue

What kind of tissue does this represent?

Where in the body can you find this tissue?

delicate thin layers between tissues; present in all mucous membranes

Loose (areolar) connective tissue

Connective Tissue



Adipose tissue

fat

Connective Tissue



Dense connective tissue

tendons; ligaments

Connective Tissue



Hyaline cartilage

nose; ends of long bones; ribs

Connective Tissue



Elastic cartilage

outer ear; epiglottis

Connective Tissue



Fibrocartilage

between vertebrae; knee joints; pubic joint

Connective Tissue



Bone

skeletal system

Connective Tissue



Blood

bloodstream

Connective Tissue

• characterized by properties that allow movement.

• muscle cells are excitable (=respond to a stimulus) + contractile (=can shorten and

generate a pulling force)

• some muscle movement is voluntary (=under conscious control) other involuntary

(ie contraction of your pupil) • classified into 3 types according to structure and function

Muscle Tissue

Muscle Tissue

• Skeletal muscle makes possible locomotion, facial expressions, posture, and other voluntary movements (40% body mass), participate in thermal homeostasis: myocyte (from myoblasts, mesoderm) and their numbers remain relatively constant throughout life. Arranged in bundles surrounded by connective tissue. striated (due to the regular alternation of the contractile proteins actin and myosin), with many nuclei squeezed along the membranes (as a result of the fusion of the many myoblasts to form each long muscle fiber).

Muscle Tissue

Skeletal muscle cells (fibers), with cross-striations and peripheral nuclei.

Muscle Tissue

Higher power of skeletal muscle for details of cross-striations. Notice thin Z discs and heavy A bands. From one Z disc to the next is a sarcomere, the unit of muscle contraction. In the upper muscle cell notice shadowy myofibrils running longitudinally.

Muscle Tissue

EM of several myofibrils running longitudinally through skeletal muscle cell. Between individual myofibrils lie the mitochondria (M) and glycogen (G) of the cytoplasm. Within each myofibril are the typical striations: A= A band; I= I band; Z= Z line; and H= H band. The banding is formed by the arrangement of myosin and actin filaments.

Muscle Tissue

• Smooth muscle responsible for involuntary movements in the internal organs. It forms the contractile component of the digestive, urinary, and reproductive systems as well as the airways and arteries. Each cell is spindle shaped with a single nucleus and no visible striations

Muscle Tissue

Smooth muscle - long, slender central nuclei, lying within narrow, fusiform cells that lie parallel to each other in a smooth arrangement. (Muscle cells are often referred to as muscle fibers because of their narrowness and length.)

Muscle Tissue

Smooth muscle - with cells more separated so as to see their extent and shape better, and the central position of their nuclei. A loose, irregular connective tissue (endomysium) lies between the cells. Nuclei seen in this c.t. belong to fibroblasts mainly.

Muscle Tissue

Smooth muscle with wrinkled nuclei due to contraction of cells.

Muscle Tissue

EM of smooth muscle showing typical "hairy" look of primarily filaments in the cytoplasm. Part of the cytoplasm is clear of filaments and shows mitochondria and polyribosomes. The cell membrane is at the lower right of the field and shows a few pinocytotic vesicles toward the extreme right. The left-hand extent of that same membrane seems darker and denser: probably a plaque, where filaments attach. The fuzzy density just outside the cell membrane is the basal lamina.

Muscle Tissue

• Cardiac muscle (contractile walls of the heart), cardiomyocytes, also striated single cells typically with a single centrally located nucleus, contract on their own intrinsic rhythms without any external stimulation and attach to one another with specialized cell junctions = intercalated discs (both anchoring junctions and gap junctions) long, branching cardiac muscle fibers that are, essentially, a mechanical and electrochemical syncytium with synchronized actions that pumps blood under involuntary control.

Muscle Tissue

Cardiac muscle with cross-striations, dark intercalated discs, and centrally located nuclei. Notice too that the nuclei are stubby in appearance, and that they lie in a rather granular cytoplasm. Some of the intercalated discs form a straight line across muscle fibers; others make a step-like arrangement.

Muscle Tissue

EM of intercalated disc between the ends of two cardiac muscle cells. Both desmosomes (1) and fasciae adheretes (2) are identified. Notice mitochondria and glycogen particles lying between myofibrils.

Muscle Tissue

Another view of cardiac muscle showing wavy connective tissue (endomysium) between muscle cells. Also, notice capillaries with r.b.c.'s; muscle is a highly vascularized tissue. Some yellow granular cytoplasm can be seen inside the lower muscle cells, where myofibrils are parted. This picture also gives some indication of the branching of cardiac fibers.

• excitable and capable of sending and receiving electrochemical signals that provide the

body with information. • 2 main classes of cells: neuron (propagate information via electrochemical impulses,

called action potentials, which are biochemically linked to the release of chemical signals) and neuroglia (play an essential role in supporting neurons and modulating their information propagation)

Nervous Tissue

Nervous Tissue

Neurons = distinctive morphology role as conducting cells, with 3 parts. The cell body includes most of the cytoplasm, the organelles, and the nucleus. Dendrites branch off the cell body and appear as thin extensions. A long “tail,” the axon, extends from the neuron body and can be wrapped in an insulating layer known as myelin, which is formed by accessory cells. The synapse is the gap between nerve cells, or between a nerve cell and its target, for example, a muscle or a gland, across which the impulse is transmitted by chemical compounds known as neurotransmitters. Neurons categorized: multipolar, bipolar and unipolar. When a neuron is sufficiently stimulated, it generates an action potential that propagates down the axon towards the synapse. If enough neurotransmitters are released at the synapse to stimulate the next neuron or target, a response is generated.

Nervous Tissue

The second class of neural cells: neuroglia or glial cells, (from the Greek word for glue).

Astrocyte cells, (star shape) abundant in the CNS, have many functions: regulation of ion

concentration in the intercellular space, uptake and/or breakdown of some neurotransmitters,

and formation of the blood-brain barrier. Microglia protect the nervous system against

infection (related to macrophages). Oligodendrocytes produce myelin in the CSN (brain and

spinal cord) while the Schwann cell produces myelin in the peripheral nervous system

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