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Bone can be divided into two types: compact and spongy. Compact bone is found in the shaft (or diaphysis) of a long bone and the surface of the flat bones, while spongy bone is found in the end (or epiphysis) of a long bone. Compact bone is organized into subunits called osteons , as illustrated in [link] . A blood vessel and a nerve are found in the center of the structure within the Haversian canal, with radiating circles of lacunae around it known as lamellae. The wavy lines seen between the lacunae are microchannels called canaliculi ; they connect the lacunae to aid diffusion between the cells. Spongy bone is made of tiny plates called trabeculae these plates serve as struts to give the spongy bone strength. Over time, these plates can break causing the bone to become less resilient. Bone tissue forms the internal skeleton of vertebrate animals, providing structure to the animal and points of attachment for tendons.

 Illustration A shows a cross section of a long bone with wide protrusions at either end. The outer part is compact bone. Inside the compact bone is porous spongy bone made of web-like trabreculae. The spongy bone fills the wide part at either end of the bone. In the middle, a hollow exists inside the spongy bone. Illustration B shows several circular osteons clustered together in compact bone. At the hub of each osteon is an opening called the Haversian canal filled with blood and lymph vessels and nerves. The lamellae surrounding the Haversian canal resemble tree rings.  Lacunae are wide spaces in the rings between the lamellae. Microchannels called canaliculi radiate through the rings out from the central Haversian canal, connecting the lacunae together. Illustration C shows small osteoclasts surrounding the outside of bone. Larger osteoclasts are also on the outer surface, forming a hollow in the bone. Osteocytes are long, thin cells in the lacunae.
(a) Compact bone is a dense matrix on the outer surface of bone. Spongy bone, inside the compact bone, is porous with web-like trabeculae. (b) Compact bone is organized into rings called osteons. Blood vessels, nerves, and lymphatic vessels are found in the central Haversian canal. Rings of lamellae surround the Haversian canal. Between the lamellae are cavities called lacunae. Canaliculi are microchannels connecting the lacunae together. (c) Osteoblasts surround the exterior of the bone. Osteoclasts bore tunnels into the bone and osteocytes are found in the lacunae.

Adipose tissue

Adipose tissue, or fat tissue, is considered a connective tissue even though it does not have fibroblasts or a real matrix and only has a few fibers. Adipose tissue is made up of cells called adipocytes that collect and store fat in the form of triglycerides, for energy metabolism. Adipose tissues additionally serve as insulation to help maintain body temperatures, allowing animals to be endothermic, and they function as cushioning against damage to body organs. Under a microscope, adipose tissue cells appear empty due to the extraction of fat during the processing of the material for viewing, as seen in [link] . The thin lines in the image are the cell membranes, and the nuclei are the small, black dots at the edges of the cells.

Illustration shows irregularly shaped cells with tiny nuclei clustered next to the cell’s outer membrane.
Adipose is a connective tissue is made up of cells called adipocytes. Adipocytes have small nuclei localized at the cell edge.


Blood is considered a connective tissue because it has a matrix, as shown in [link] . The living cell types are red blood cells (RBC), also called erythrocytes, and white blood cells (WBC), also called leukocytes. The fluid portion of whole blood, its matrix, is commonly called plasma.

Different types of blood cells are shown. Red blood cells are disc-shaped, with a central indentation. Platelets are much smaller than red blood cells, narrow and long. Neutrophils, eosinophils, lymphocytes, monocytes and basophils are all about three times the diameter of a red blood cell and round. They differ in the shape of the nucleus, and in the presence or absence of granules in the cytoplasm. Macrophages, which are the largest cell type, have pseudopods which give them an irregular shape.
Blood is a connective tissue that has a fluid matrix, called plasma, and no fibers. Erythrocytes (red blood cells), the predominant cell type, are involved in the transport of oxygen and carbon dioxide. Also present are various leukocytes (white blood cells) involved in immune response.

The cell found in greatest abundance in blood is the erythrocyte. Erythrocytes are counted in millions in a blood sample: the average number of red blood cells in primates is 4.7 to 5.5 million cells per microliter. Erythrocytes are consistently the same size in a species, but vary in size between species. For example, the average diameter of a primate red blood cell is 7.5 µl, a dog is close at 7.0 µl, but a cat’s RBC diameter 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 made. Fish, amphibian, and avian red blood cells maintain their nuclei and mitochondria throughout the cell’s life. The principal job of an erythrocyte is to carry and deliver oxygen to the tissues.

Questions & Answers

Is the "growth and maintenance phase" in a cell's life cycle when cell division is about to occur
Somto Reply
what is the common name of Basidiomycetes
Ogechukwu Reply
الاجزاء النباتية لابد من تعقيمها قبل زراعتها في القوارير
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Shahzad Reply
which are present In Body And such elements Have Great role in our Body there are 16 bio elements that maintains human Body but on The basis of amount There are 6 bio elements present in Concen. of 99% and More Valuable And Highly Concen. element is Oxygent with 65 %
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describe the anatomy of cell division
Ivanovic Reply
Complex traits such as height result from 
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Nkalubo Reply
chloroplast in plants and bacterial cell ; mitochondria in animal cells
Diagram of a living cell
Eliza Reply
what is cell
A cell is the smallest basic unit of life.
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Ogochukwu Reply
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Nutty Reply
Describe the structure of starch?
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water is life!.. Discuss?
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Dennis Reply
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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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