5.6: connective tissue (2023)

to develop skills

  • Describe epithelial tissue.
  • Discuss the different types of connective tissue in animals.
  • Describe three types of muscle tissue.
  • Describe nerve tissue.

The tissues of complex multicellular animals are of four main types: epithelial, connective, muscular, and neural. Remember that tissues are groups of similar cells, a group of similar cells that perform related functions. These tissues combine to form organs such as the skin or kidneys, which have specific, specialized functions in the body. Organs are organized into organ systems to perform functions; Examples are the circulatory system, which is made up of the heart and blood vessels, and the digestive system, which is made up of various organs including the stomach, intestines, liver, and pancreas. Organ systems together form a complete organism.


EpithelgewebeThey cover the exterior of organs and structures in the body and line the lumens of organs in a single layer or multiple layers of cells. The types of epithelium are classified according to the shape of the cells present and the number of cell layers. Epithelia formed by a single layer of cells are calledsimple epithelium; Epithelial tissue composed of several layers is calledstratified epithelium. The table summarizes the different types of epithelial tissues.

Table \(\PageIndex{1}\):Different types of epithelial tissue
Zellform Description Location
scaly flat, irregular round shape simple: alveoli, layered capillaries: skin, mouth, vagina
cubic cuboid central core glands, renal tubules
the pillar high, narrow, nucleus towards the base high, narrow, nucleus along the cell simple: digestive tract, pseudostratified: respiratory tract
transition round, simple, but seemingly complex bladder

squamous epithelium

squamous epitheliumCells are generally round, flat, and have a small nucleus in the middle. The cell outline is slightly irregular and the cells fit together to form a cover or lining. When cells are arranged in a single layer (simple epithelium), they facilitate diffusion into tissues such as B. Gas exchange areas in the lungs and the exchange of nutrients and waste products in blood capillaries.

5.6: connective tissue (1)

Figure \(\PageIndex{1}\) shows a layer of squamous epithelial cells whose membranes are connected to form an epithelium. The figure \(\PageIndex{1}\) shows squamous epithelial cells arranged in stratified layers where protection is needed in the body from external abrasion and damage. This is called stratified squamous epithelium and occurs in the skin and tissues lining the mouth and vagina.

cuboid epithelium

cuboid epitheliumThe cells shown in figure \(\PageIndex{2}\) are cuboidal with a single central nucleus. They are most commonly found in a single layer, which is a simple epithelium, in glandular tissues throughout the body, where they prepare and secrete glandular material. They are also found in the walls of the tubules and in the ducts of the kidneys and liver.

5.6: connective tissue (2)

Columnar epithelium

columnar epitheliumCells are taller than they are wide: they resemble a stack of columns in a layer of epithelium and are most commonly found in a monolayer arrangement. The nuclei of the columnar epithelial cells of the digestive tract appear to be aligned at the base of the cells, as shown in figure \(\PageIndex{3}\). These cells absorb material from the lumen of the digestive tract and prepare it for entry into the body through the circulatory and lymphatic systems.

5.6: connective tissue (3)

The columnar epithelial cells lining the airways appear to be stratified. However, each cell is attached to the basement membrane of the tissue and hence they are simple tissues. The cell nuclei are arranged at different levels in the cell layer, which makes it appear that there is more than one layer, as can be seen in figure \(\PageIndex{4}\). Calledpseudostratified, columnar epithelium. This cell covering has cilia on the apical or free surface of the cells. Cilia improve the movement of trapped particles and mucus from the airways and help protect the system from invading microorganisms and harmful materials that have been inhaled into the body. Goblet cells are scattered in some tissues (eg, the lining of the trachea). The goblet cells contain mucus that traps irritants, which in the case of the trachea prevents those irritants from reaching the lungs.

5.6: connective tissue (4)

transitional epithelium

crossingor uroepithelial cells are found only in the urinary system, mainly in the bladder and ureter. These cells are arranged in a stratified layer, but can stack on top of each other in an empty, relaxed bubble, as shown in figure \(\PageIndex{5}\). As the bladder fills, the epithelial layer unfolds and expands to accommodate the volume of urine that enters it. As the bladder fills, it expands and the lining thins. In other words, the fabric goes from thick to thin.

5.6: connective tissue (5)

A practice

Which of the following statements about epithelial cell types is incorrect?

  1. Simple columnar epithelial cells line the lung tissue.
  2. Simple cuboid epithelial cells are involved in filtering the blood in the kidney.
  3. Pseudostratified columnar epithelia appear in a single layer, but the arrangement of the nuclei suggests that more than one layer is present.
  4. The transitional epithelium changes thickness depending on how full the bladder is.


connective tissue

connective tissueThey consist of a matrix made up of living cells and a non-living substance called the ground substance. The basic substance consists of an organic substance (usually a protein) and an inorganic substance (usually a mineral or water). The main cell of connective tissue is the fibroblast. This cell produces the fibers found in almost all connective tissues. Fibroblasts are motile, capable of mitosis, and able to synthesize any connective tissue needed. Macrophages, lymphocytes, and occasionally leukocytes can be found in some tissues. Some tissues have specialized cells not found in others. Heheadquartersin the connective tissue it gives density to the tissue. When a connective tissue has a high concentration of cells or fibers, it has a proportionally less dense matrix.

The organic parts or protein fibers found in the connective tissue are collagenous, elastic or reticular fibers. Collagen fibers give the fabric strength and prevent it from tearing or detaching from the surrounding tissue. Elastic fibers are made from the protein elastin; This fiber can stretch to half its length and return to its original size and shape. Elastic fibers give fabrics flexibility. Reticular fibers are the third type of protein fibers found in connective tissue. This fiber is made up of fine strands of collagen that form a fibrous network to support the tissues and other organs to which it is connected. The table summarizes the different types of connective tissue, the types of cells and fibers that make them up, and the locations of the tissue samples.

Table \(\PageIndex{2}\):connective tissue
tissue cells fibers Location
locker/areolar fibroblasts, macrophages, some lymphocytes, some neutrophils few: collagen, elastic, reticular around blood vessels; anchoring epithelium
dense, fibrous connective tissue fibroblasts, macrophages, mainly collagen irregular: normal skin: tendons, ligaments
cartilage chondrocytes, chondroblasts hyaline: little collagen fibrous cartilage: lots of collagen Shark skeleton, fetal bones, human ears, intervertebral discs
Osso Osteoblasts, Osteozytes, Osteoclasts some: collagen, elastic Vertebrate skeletons
fett Adipocytes some obese (fat)
blood red blood cells, white blood cells none blood

loose/areolar connective tissue

Loose connective tissue, also called areolar connective tissue, contains a sample of all components of a connective tissue. As shown in figure \(\PageIndex{6}\), the loose connective tissue shows some fibroblasts; Macrophages are also present. Collagen fibers are relatively wide and stain light pink, while elastic fibers are thin and stain dark blue to black. The space between the formed tissue elements is filled with the matrix. The material in the connective tissue gives it a fluffy consistency similar to a stretched cotton ball. Loose connective tissue surrounds each blood vessel and helps hold the vessel in place. Tissue is also found around and between most organs in the body. In summary, areolar tissue is tough yet flexible and comprises membranes.

5.6: connective tissue (6)

Fibrous connective tissue

fibrous connective tissuethey contain large amounts of collagen fibers and few cells or matrix material. The fibers can be arranged irregularly or regularly with strands aligned in parallel. Irregularly arranged fibrous connective tissues are found in areas of the body where stress occurs in all directions, such as in the dermis of the skin. Normal fibrous connective tissue, shown in figure \(\PageIndex{7}\), is found in tendons (connecting muscles to bone) and ligaments (connecting bone to bone).

5.6: connective tissue (7)


cartilageIt is a connective tissue with a large amount of matrix and a variable amount of fibers. The cells, calledchondrocytes, form the matrix and fibers of the tissue. Chondrocytes reside in spaces within tissues called chondrocytesGaps.

A cartilage with few collagen and elastic fibers is hyaline cartilage, shown in figure \(\PageIndex{8}\). The gaps are randomly scattered throughout the tissue, and the matrix appears milky or rubbed in routine histological stains. Sharks have cartilaginous skeletons, as do almost all human skeletons at some stage of prenatal development. A remnant of this cartilage persists outside of the human nose. Hyaline cartilage is also found at the ends of long bones, which reduces friction and cushions the joints of those bones.

5.6: connective tissue (8)

Elastic cartilage has a large number of elastic fibers, giving it great flexibility. The ears of most vertebrates contain this cartilage, as do parts of the larynx, or larynx. Fibrous cartilage contains a large number of collagen fibers that give the tissue enormous strength. Fibrous cartilage comprises the intervertebral discs in vertebrates. The hyaline cartilage in mobile joints such as the knee and shoulder is damaged by age or trauma. Damaged hyaline cartilage is replaced with fibrocartilage and causes the joints to become "stiff".


Bone, or bone tissue, is connective tissue that contains a large amount of two different types of matrix material. The organic matrix resembles matrix material found in other connective tissues and contains some collagen and elastic fibers. This gives the fabric strength and flexibility. The inorganic matrix consists of mineral salts, mainly calcium salts, which impart hardness to the tissue. Without sufficient organic material in the matrix, tissue degrades; without suitable inorganic material in the matrix, the tissue bends.

There are three types of cells in bone: osteoblasts, osteocytes and osteoclasts. Osteoblasts are active in producing bone for growth and remodeling. Osteoblasts deposit bone material in the matrix and continue to live after the matrix surrounds them, but in a reduced metabolic state as osteocytes. Osteocytes are located in the gaps in the bone. Osteoclasts are active in bone remodeling for bone remodeling and provide access to calcium stored in tissues. Osteoclasts are usually found on the tissue surface.

Bones can be divided into two types: compact and spongy. Compact bone is found at the shaft (or shaft) of a long bone and on the surface of flat bones, while cancellous bone is found at the end (or epiphysis) of a long bone. Compact bone is organized into subunits calledOsteonasen, as shown in figure \(\PageIndex{9}\). A blood vessel and nerve are at the center of the structure within Haversian canal, surrounded by radiating circles of gaps known as lamellae. The wavy lines between the gaps are called microchannelscanals; They plug the gaps to help spread between cells. Cancellous bone consists of small plates calledbunchThese plates serve as supports to give strength to the cancellous bone. Over time, these plates can break, causing the bone to become weaker. Bone tissue forms the internal skeleton of vertebrates and provides the animal with structure and attachment points for tendons.

5.6: connective tissue (9)

adipose tissue

Adipose tissue, or adipose tissue, is considered connective tissue even though it has no fibroblasts or matrix proper and few fibers. Adipose tissue is made up of cells called adipocytes, which collect and store fat in the form of triglycerides for energy metabolism. Adipose tissue also serves as insulation to maintain body temperature, allowing animals to be endothermic and acting as a buffer against damage to body organs. Under the microscope, adipose tissue cells appear empty due to the removal of fat during processing of the material for visualization, as shown in figure \(\PageIndex{10}\). The thin lines in the image are the cell membranes, and the nuclei are the small black dots at the edges of the cells.

5.6: connective tissue (10)


Blood is considered connective tissue because it has a matrix as shown in figure \(\PageIndex{11}\). The types of living cells are red blood cells (erythrocytes), also called erythrocytes, and white blood cells (leukocytes), also called leukocytes. The liquid part of whole blood, its matrix, is commonly referred to as plasma.

5.6: connective tissue (11)

The most common cell in the blood is the erythrocyte. The number of red blood cells in a blood sample is in the millions: the average number of red blood cells in primates is 4.7 to 5.5 million cells per microliter. Red blood cells are consistently the same size within a species but vary in size between species. For example, the average diameter of the red blood cells in a primate is 7.5 µl, in a dog almost 7.0 µl, but the diameter of the red blood cells in a cat is 5.9 µl. Sheep erythrocytes are even smaller at 4.6 µl. Mammalian erythrocytes lose their nuclei and mitochondria when they are released from the bone marrow, where they are produced. Red blood cells in fish, amphibians, and birds maintain their nuclei and mitochondria throughout the cell's lifespan. The main task of an erythrocyte is to transport and deliver oxygen to the tissue.

Leukocytes are the predominant white blood cells in the peripheral blood. The number of white blood cells in the blood is in the thousands, with measurements expressed as ranges: the number in primates ranges from 4,800 to 10,800 cells per µl, in dogs from 5,600 to 19,200 cells per µl, in cats from 8,000 to 25,000 cells per µl, in cattle from 4,000 to 12,000 cells per µl and in pigs from 11,000 to 22,000 cells per µl.

Lymphocytes act primarily in the immune response to foreign antigens or materials. Different types of lymphocytes produce antibodies adapted to foreign antigens and control the production of these antibodies. Neutrophils are phagocytes and participate in one of the first lines of defense against microbial invaders by helping to eliminate bacteria that have entered the body. Another leukocyte found in the peripheral blood is the monocyte. Monocytes give rise to phagocytic macrophages, which remove dead and damaged cells from the body, whether foreign or from the host animal. Two other leukocytes in the blood are eosinophils and basophils that help facilitate the inflammatory response.

The slightly granular material between the cells is a cytoplasmic fragment of a bone marrow cell. This is called a platelet or thrombocyte. Platelets are involved in the steps that lead to blood clotting to stop bleeding from damaged blood vessels. Blood has multiple functions, but primarily it carries material around the body, to carry nutrients to cells and to remove waste from cells.

muscle tissue

There are three types of muscle in the animal body: smooth, skeletal, and cardiac. They are distinguished by the presence or absence of stripes or bands, the number and location of nuclei, whether they are controlled voluntarily or involuntarily, and their location in the body. The table summarizes these differences.

Table \(\PageIndex{3}\):muscle types
type of muscle Stretch marks Nuclear Check Location
Together NO alone in the middle involuntarily visceral organs
skeletal Sim Many on the periphery voluntarily Skelettmuskeln
Herz Sim alone in the middle involuntarily Herz

smooth muscle cells

Smooth muscle has no stripes in its cells. It has a single core located in the middle as shown in figure \(\PageIndex{12}\). Smooth muscle constriction occurs under involuntary autonomic nerve control and in response to local tissue conditions. Smooth muscle tissue is also referred to as non-striated because it does not have the banded appearance of cardiac and skeletal muscle. The walls of blood vessels, the ducts of the digestive system, and the ducts of the reproductive system are composed primarily of smooth muscle.

5.6: connective tissue (12)

skeletal muscles

Skeletal muscle has streaks along its cells caused by the arrangement of the contractile proteins actin and myosin. These muscle cells are relatively long and have multiple nuclei at the edge of the cell. Skeletal muscle is under the voluntary control of the somatic nervous system and resides in the muscles that move bones. Figure \(\PageIndex{12}\) illustrates the histology of skeletal muscle.


The heart muscle, shown in figure \(\PageIndex{12}\), only occurs in the heart. Like skeletal muscle, it has transverse stripes in its cells, but cardiac muscle has a single, centrally located nucleus. The heart muscle is not under voluntary control but can be influenced by the autonomic nervous system to speed up or slow down. An additional feature of heart muscle cells is a line that runs along the edge of the cell when it rests on the next heart cell in the line. This line is called the intercalated disc: it helps conduct the electrical impulse efficiently from one cell to another and maintains the strong connection between adjacent heart cells.

nerve tissue

Nerve tissues are made up of specialized cells that receive and transmit electrical impulses from specific areas of the body and send them to specific locations in the body. The main cell of the nervous system is the neuron, shown in figure \(\PageIndex{13}\). The large structure with a central nucleus is the cell body of the neuron. Cell body projections are dendrites specialized to receive information or a single axon specialized to transmit impulses. Some glial cells are also shown. Astrocytes regulate the chemical environment of the nerve cell, and oligodendrocytes insulate the axon so that the nerve's electrical impulse is transmitted more efficiently. Other glial cells, not shown, fulfill the neuron's nutritional and waste requirements. Some of the glial cells are phagocytic, removing debris or damaged cells from tissues. A nerve consists of neurons and glial cells.

5.6: connective tissue (13)

link to learning

5.6: connective tissue (14)

click nointeractive reviewto learn more about epithelial tissue.

Professional Connections: Pathologist

A pathologist is a doctor or veterinarian who specializes in the laboratory detection of disease in animals, including humans. These professionals complete their education in medical school and follow it with an extensive postgraduate residency in a medical center. A pathologist may oversee clinical laboratories to examine body tissues and blood samples for disease or infection. They examine tissue samples through a microscope to identify cancer and other diseases. Some pathologists perform autopsies to determine cause of death and disease progression.


The basic components of complex animals are four primary tissues. These combine to form organs that have a specific and specialized function in the body, such as the skin or the kidneys. Organs are organized together to perform common functions in the form of systems. The four primary tissues are epithelium, connective tissue, muscle tissue, and neural tissue.


Microchannel that connects gaps and facilitates diffusion between cells
Type of connective tissue with large amounts of ground substance matrix, cells called chondrocytes, and some fibers
Cell found in cartilage
Columnar epithelium
Epithelium composed of cells that are larger than wide and specialized for absorption
connective tissue
Type of tissue composed of cells, ground substance matrix and fibers
cuboid epithelium
Cubic cell epithelium specialized in glandular functions
Tissue lining or covering organs or other tissues
Fibrous connective tissue
Type of connective tissue with a high concentration of fibers
Space in cartilage and bone that contains living cells
loose connective tissue (areolar)
connective tissue type with low cell, matrix and fiber count; found around blood vessels
Component of connective tissue made up of living and non-living cells (basic materials)
compact bone subunit
Epithelial layer that appears multi-layered but is a simple covering
simple epithelium
single layer of epithelial cells
squamous epithelium
Type of flat-cell epithelium specialized to aid in diffusion or to prevent abrasion
stratified epithelium
several layers of epithelial cells
small plate that forms spongy bone and gives it strength
transitional epithelium
epithelium that can change from stratified to simple; also called uroepithelium
Top Articles
Latest Posts
Article information

Author: Prof. Nancy Dach

Last Updated: 04/26/2023

Views: 5518

Rating: 4.7 / 5 (57 voted)

Reviews: 88% of readers found this page helpful

Author information

Name: Prof. Nancy Dach

Birthday: 1993-08-23

Address: 569 Waelchi Ports, South Blainebury, LA 11589

Phone: +9958996486049

Job: Sales Manager

Hobby: Web surfing, Scuba diving, Mountaineering, Writing, Sailing, Dance, Blacksmithing

Introduction: My name is Prof. Nancy Dach, I am a lively, joyous, courageous, lovely, tender, charming, open person who loves writing and wants to share my knowledge and understanding with you.