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Cardiovascular System

8.1 Overview The cardiovascular system consists of the heart —a muscular pump—and closed vessels through which blood circulates in the body. Arteries leave the heart, branch repeatedly, and have smaller diameters as they course toward the periphery. They deliver blood to capillaries , which are the thinnest vessels and are closest to body cells. Blood in capillaries is returned to the heart via veins . The…

Blood and Bone Marrow

7.1 Overview Blood is a specialized type of connective tissue that consists of cells suspended in a circulating fluid known as plasma. The total amount of circulating blood in men is 5-6 L; that in women, 4-5 L. Fresh blood is a red, viscous fluid, whereas plasma is translucent and yellow. Cellular elements of blood constitute about 45% of blood volume in adults, with plasma making up the…

Cartilage and Bone

6.1 Overview Cartilage and bone are specialized forms of connective tissue that have critical roles in providing the skeletal framework of the body. Although they share similarities, many important differences set them apart. As with other connective tissues, they derive from embryonic mesenchyme; both consist of cells embedded in an extracellular matrix. Cartilage matrix is a firm yet resilient gel, with physical attributes of a plastic;…

Nervous Tissue

5.1 Overview The nervous system is divided anatomically into the central (CNS) and peripheral (PNS) nervous systems. The CNS comprises the brain, brainstem , and spinal cord ; the PNS, all nerve fibers ( axons and dendrites ), nerve endings , and collections of their cell bodies that lie outside the CNS. The autonomic nervous system , a subdivision of the PNS, is connected to the…

Muscle Tissue

4.1 Overview Muscle tissue in the body is classified into one of three major categories according to structure, function, and location. Skeletal muscle is the most common and characteristic type; the other two kinds are cardiac muscle and smooth muscle. Skeletal muscle produces purposeful movements of the skeleton. Cardiac muscle forms the myocardium and is responsible for beating of the heart to pump blood. Smooth muscle…

Connective Tissue

3.1 Overview Adult connective tissue comprises a diverse family of tissues whose major function is to provide form and support to the body and organs and to connect and anchor parts. It is also a medium for exchange of nutrients, oxygen, and waste products between other tissues; it aids in defense and protection; and in certain sites, as in adipose tissue, it stores fat for cushioning…

Epithelium and Exocrine Glands

2.1 Overview Epithelium is one of the four basic tissues, with a wide distribution and many functions. It consists of continuous sheets of cells that cover exposed body surfaces. It also lines internal cavities, such as those of the digestive, respiratory, cardiovascular, and genitourinary systems. During embryonic development, epithelium invaginates into underlying tissues to proliferate and form secretory glands. Its two classes are thus covering and…

The Cell

1.1 Overview The human body is organized into four basic tissues ( epithelial , muscle , nervous , and connective ) that consist of cells and associated extracellular matrix. The cell is the fundamental structural and functional unit of all living organisms. The body contains about 60 × 10 12 cells—some 200 different types whose size and shape vary widely—but all have a common structural plan.…

Sensory Organs

Eye The eyeball is formed by three distinct layers. The outermost fibrous corneoscleral layer comprises the translucent cornea and the nontransparent sclera. The middle layer is the uvea, a vascular layer that also includes the choroid (choroidea) as well as the stroma of the ciliary body and the iris. The innermost coat is the retina that surrounds the vitreous chamber. Cornea is composed of a corneal…

Nervous System

Nervous tissue Nervous tissue forms the parenchyma of the nervous system, and it is composed of neurons and glial cells. The major glial cell types of the central nervous system (CNS) are the astrocytes (astroglia), oligodendrocytes (oligodendroglia) microglia and ependymal cells, while peripheral nervous system (PNS) contains Schwann cells and satellite cells. Detailed description of the cells populating the nervous system is given in Chapter I…

Endocrine System

Hypophysis (pituitary gland) Hypophysis, together with the hypothalamus is considered to be the master organ of the endocrine system influencing all the endocrine functions of the body. It is composed of an anterior lobe (adenohypophysis) that derives from the ectoderm of the oropharynx (Rathke’s pouch) and the posterior lobe (neurohypophysis) that is developing from the neuroectoderm, and thus it is part of the central nervous system.…

Female Reproductive System

Ovary Ovary is covered by a single layer of low cuboidal cells (germinal epithelium) that transitions into a mesothelial cell lining near the mesovarium. The epithelium is attached to a dense connective tissue tunica albuginea that is thinner than the one in the testis. The parenchyma of the ovary is composed of the outer cortex, containing the ovarian follicles embedded into a cell rich stroma, and…

Male Reproductive System

Testis and epididymis Most of the testis and the epididymis are covered with a thin serous membrane layer, the tunica vaginalis, which is formed by mesothelial cells and the underlying loose connective tissue lamina propria serosae. Under the tunica vaginalis, testis is enclosed by a thick dense connective tissue capsule, the tunica albuginea that rests on a thin, vascular, loose connective tissue tunica vasculosa. Tunica albuginea…

Respiratory System

Nasal cavity The initial part of the airways are the nasal cavities that – apart from the vestibule, the cavity of the external nose that is lined with stratified squamous keratinized epithelium – are covered with kinociliated pseudostratified columnar epithelium with goblet cells and occasional sensory brush cells. The lamina propria under the epithelium is attached to the periosteum of the underlying bone and contains scattered…

Digestive System II: Lower Alimentary Tract

Esophagus The mucous membrane of the esophagus (oesophagus) is covered by stratified squamous nonkeratinized epithelium. The lamina propria is composed of loose connective tissue with lymphatic elements that form occasional lymphatic follicles. The muscularis mucosae is remarkably thick and it is formed by longitudinally arranged smooth muscle bundles. The underlying submucosa is composed of dense irregular connective tissue with occasional ganglion cells and nerve fibers (Meissner’s…

Digestive System I: Upper Alimentary Tract

Layers of the gastrointestinal tract The wall structure of the tubular (hollow) organs follows a general organization that is uniform along the gastrointestinal tract. The lumen of the organs is covered with tunica mucosa (mucous membrane) that is composed of the superficial epithelial lining , the underlying lamina propria mucosae and the tunica muscularis mucosae . Lamina propria is composed of loose connective tissue that often…