BIOL 101L – ZOOLOGY LABORATORY EXERCISE 3 - ORGANS

OrganOrgan

  • a ==tissue complex== associated with performing some general bodily functions
  • Organs (lungs, heart, kidney, etc.) of higher organisms are exceedingly diverse and intricate with respect to tissue arrangement.
  • the specific kinds and amounts of tissues present are related to the function of the organ.
  • no organ of the body operates in isolation.
  • Each is ==structurally and functionally integrated== with a number of other organs.

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OrganSystemOrgan System

  • a @@specialized system@@ consisting of series of organs arranged in a particular way, and cooperative to perform one of the general functions of the body.
  • various organs @@contribute to the functioning of the entire organism@@.

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@@Types of Organs@@

^^A. Frog Skin^^

  • a part of the %%Integumentary System%%
  • forms the %%outermost covering%% of the body

==Functions:==

  • physicalprotectionphysical protection
  • biologicalprotectionbiological protection against invasion of foreign organisms
  • respirationrespiration, the exchange of oxygen and carbon dioxide
  • productionofusefulsecretionsproduction of useful secretions like mucus to keep the skin moist and slippery to avoid capture by enemies, and poisons to paralyze the enemies

==Parts of the Skin:==

  • %%Epidermis%% – from outer layers:   * ^^cornified layer^^ – outermost, very thin acellular layer and often partly broken.   * ^^intermediate layer^^ – consisting of lined squamous cells.   * ^^germinative layer^^ (Malphigan) – low columnar cells with large nuclei.   * ^^epidermal glands^^ – multicellular; their bases extending into dermis. These glands are of two types:     * @@mucus gland@@ – club-shaped, composed of mucus-secreting cells; with distinct ducts.     * @@poison glands@@ – circular, filled with small pink granules.   * ^^pigment granules^^ – scattered minute, blackish spots
  • %%Dermis%% – the thicker inner layer is mainly connective tissue and differentiated into:   * ^^spongy part^^ – scattered fibrous connective tissue below the epidermis; contains blackish chromatophores (pigment cells).   * ^^middle part^^ – layers of alternately crossed layers of connective tissue fibers; with few nuclei.   * ^^inner part^^ – thin, compact, just above lymph spaces beneath skin.

\ ^^B. Small Intestine^^

  • The @@longest portion@@ of the digestive tract.
  • It is @@slender and neatly coiled@@ within the body cavity.

==Parts of the Small Intestine:==

  • %%lumen%% – the interior cavity.
  • %%mucosa%% – the inner layer of columnar epithelium and scattered goblet cells; produces sticky mucus.
  • %%submucosa%% – next to the mucosa, a layer of spongy fibrous connective tissue that contains b__lood vessels__, nerves, and bases of multicellular glands that open into the lumen.
  • %%muscularis%% – layer of smooth muscle cells; consists of two parts:   * a thick inner layer of circular muscles (that go around the intestine)   * thinner outer part of longitudinal smooth muscle cells arranged somewhat in bundles and are cut transversely
  • %%serosa%% – very thin (one cell thick) outermost layer, of squamous cells with connective tissue beneath it; produces watery or serous secretions. This is the peritoneum that covers this organ and other organs within the body cavity.

[Fibrous connective tissue with transparent gelatinous matrix binds the various layers together.]

\ ^^C. Liver^^

  • The @@largest organ in mammals@@
  • @@Performs various functions@@, including the manufacture of bile salts used for emulsification and absorption of fatty substances
  • @@made up of lobules@@, which in turn are composed of rows of liver cells

==Parts of the Liver:==

  • %%liver cells%% – polygonal or cuboidal cells with darkly stained nuclei; these make up most of the section.
  • %%Hepatic portal canal%% – the site where the portal vein, hepatic artery, bile duct, nerves and lymphatic vessels enter or leave the liver. The portal vein, hepatic artery and bile duct form a triad through the connective tissues surrounding the hepatic lobule.   * ^^portal vein^^ – irregular cavity filled with blood cells.   * ^^hepatic artery^^ – hollow structure with thick boundary; appears more rounded than the portal vein.   * ^^bile duct^^ – cavity lined with cuboidal epithelium.
  • %%bile canaculi%% or %%bile capillaries%% – spaces between rows of cuboidal epithelium arranged in rows.

\ ^^D. Kidney^^

  • the @@major excretory organ@@ of most vertebrates
  • @@cleanses the blood@@ of impurities and waste products and helps maintain the osmotic concentration of the body

==Parts of the Kidney:==

  • %%renal portal vein%% – large blood vessel found towards the more pointed end of the section (lateral).
  • %%ureter%% or %%mesonephric duct%% – large tube extending from the kidney.
  • %%renal blood vessels%% – the renal vein and renal artery.
  • %%cortex%% – forms the outer rim of the kidney, and contains the microscopic renal corpuscles.
  • %%medulla%% – more centrally located, and contains the tubular portions of the nephron.
  • %%renal pelvis%% – large collecting duct that connects with the ureter.
  • %%renal corpuscles%% or %%Malphigian bodies%% – these are the ventrally located round masses consisting of the:   * ^^glomerulus^^ – a network of blood capillaries through which waste materials from the blood are forced to pass.   * ^^Bowman’s capsule^^ – double-membraned cup-shaped structure that surrounds the glomerulus. This receives the filtrate from the glomerulus and connects with the renal tubule at the distal end.
  • %%renal%% or %%uriniferous tubules%% – the intricately coiled narrow passageways lined by a layer of cuboidal epithelium. It consists of three distinct regions, named after their relative location and shapes, the:   * ^^proximal convoluted tubule^^   * ^^loop of Henle^^   * ^^distal convoluted tubule^^

[Because of the coiling, tubules may appear circular in some parts of the section and cylindrical in others. The central cavity is also called lumen. Small blood vessels may be observed between the tubules.]

\ ^^E. Spinal Cord^^

  • (together with the brain) @@makes up part of the Central Nervous System@@
  • @@found inside the neural cavity@@ of the vertebral column or backbone

==Parts of the Spinal Cord:==

  • %%dura mater%% – the outermost covering.
  • %%arachnoid mater%% – the material between dura mater and pia mater. The name is derived from its web-like appearance under extremely high magnification.
  • %%pia mater%% – thin membrane between the dura matter and white matter.
  • %%white matter%% – the outer portion of the spinal cord which consists of medullated nerve fibers originating from the grey matter.
  • %%gray matter%% – the innermost H-shaped mass of tissues surrounding the central canal, consisting of compactly arranged cell bodies and neuroglial cells. This part has “horn-like” corners. Note the cells with large neclei present in the ventral horn. These are motor cells.
  • %%central canal%% – the small cavity at the center of the section surrounded by ependymal cells.
  • %%spinal artery%% – the blood vessel enclosed in the ventral fissure.
  • %%Ventral and dorsal fissures%% – ventral and dorsal indentations. The ventral fissure is wider and deeper compared to the dorsal fissure.

\ ^^F. Ovary^^

  • a @@female reproductive organ@@
  • @@stores eggs@@ in various stages of maturity

==Parts of the Ovary:==

  • %%theca externa%% – the outermost membrane of the ovary.
  • %%theca interna%% – a thin layer of cells below the theca externa; that surrounds the egg chambers.
  • %%ovarian follicle%% – the rounded structures that contain the oocyte; a small portion of the theca externa, the theca interna, and the surrounding small cells between the theca interna and the oocyte are called follicle cells.
  • %%oocyte%% – maturing egg, much larger than oogonia.
  • %%oogonia%% – (sing. Oogonium) developing eggs found outside of the maturing follicle and next to the theca externa

\ ^^G. Testis^^

  • the @@male counterpart of the ovaries@@
  • @@produce great numbers of sperms@@ from stem cells

==Parts of the Testis:==

  • %%tunica propia%% – the membrane bounding the seminiferous tubules.
  • %%spermatogonia%% – small cells at the periphery of the tubule.
  • %%spermatocyte%% – bigger cells next to the spermatogonia.
  • %%spermatids%% – the darkly stained spherical cells with short tails next to the spermatocyte.
  • %%sperms%% – centrally located cells, with deeply stained heads and tails projecting into the lumen of the tubule.
  • %%Sertoli cells%% – columnar cells that protect and nurture sperm cells; also known as nurse cells. The heads of mature sperms are embedded in these cells.
  • %%tunica albuginea%% – outer fibromuscular covering of the testis.
  • %%interstitial cells%% – cluster of tiny cells between the seminiferous tubules.

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