Organic Compounds PDF

Organization levels 1  Organic compounds The four types most important to human structure and function are: carbohydrates, lipids, proteins, and nucleotides. 1- Carbohydrate is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are fo...

Organization levels 1  Organic compounds The four types most important to human structure and function are: carbohydrates, lipids, proteins, and nucleotides. 1- Carbohydrate is a molecule composed of carbon, hydrogen, and oxygen; in most carbohydrates, hydrogen and oxygen are found in the same two-to- one relative proportions they have in water. In fact, the chemical formula for molecule of carbohydrate is (CH2O)n. ▪Carbohydrates are referred to as saccharides, a word meaning “sugars.” Three forms are important in the body. Monosaccharides (mono = one)are the monomers of carbohydrates. Disaccharides (di = two) are made up of two monomers. Polysaccharides are the polymers, and can consist of hundreds to thousands of monomers. 2 Monosaccharides include: sugars, glucose, fructose, and galactose (hexose). ribose and deoxyribose (pentose) disaccharide is a pair of monosaccharides. Disaccharides are formed via dehydration synthesis. These are sucrose, commonly referred to as table sugar; lactose, or milk sugar; and maltose, or malt sugar. Polysaccharides Polysaccharides can contain a few to a thousand or more monosaccharides. Three are important to the body: Starches are polymers of glucose. Glycogen is also a polymer of glucose, but it is stored in the tissues of animals, especially in the muscles and liver. Cellulose, a polysaccharide that is the primary component of the cell wall of green plants, is the component 3 of plant  Structure of carbohydrates 4  2- Lipids A lipid is one of a highly diverse group of compounds made up mostly of hydrocarbons. The few oxygen atoms they contain. They are used in the body for: insulation protection of body parts energy storage. Their nonpolar hydrocarbons make all lipids hydrophobic. In water, lipids do not form a true solution, but they may form an emulsion, which is the term for a mixture of solutions that do not mix well. lipids include: Triglycerides, phospholipid, and steroid Triglycerides (referred to as a fat) A triglyceride is one of the most common dietary lipid groups, and5 the type found most abundantly in body tissues. This compound is formed from the synthesis of two types of molecules: A glycerol backbone at the core of triglycerides, consists of three carbon atoms. Three fatty acids, long chains of hydrocarbons with a carboxyl group and a methyl group at opposite ends, extend from each of the carbons of the glycerol. phospholipids are similar in structure to triglycerides. However, instead of having three fatty acids, a phospholipid is generated from a diglyceride, a glycerol with just two fatty acid chains. Steroid has four hydrocarbon rings bonded to a variety of other atoms and molecules sterols synthesize in both plants and animals cholesterol in human structure and function is, which is synthesized by the liver in humans Sex hormoners 6  Structure of Triglycerides Structure of fatty acids 7  Structure of phospholipids Structure of Steroids 8  3- protein protein is an organic molecule composed of amino acids linked by peptide bonds. Proteins include the keratin in the epidermis of skin that All proteins also contain nitrogen (N), and many contain sulfur (S), in addition to carbon, hydrogen, and oxygen. Proteins are polymers made up of nitrogen-containing monomers called amino acids. An amino acid is a molecule composed of an amino group NH2 and a carboxyl group COOH, together with a variable side chain. Just 20 different amino acids The unique bond holding amino acids together is called a peptide bond. 9 When two amino acids join up the reaction expels a molecule of water and the resulting bond is called a peptide bond. Important groups of biologically active substances are proteins, e.g.: carrier molecules, e.g. haemoglobin enzymes many hormones, e.g. insulin antibodies Proteins can also be used as an alternative energy source, usually in dietary inadequacy, although the process is much less efficient than when carbohydrates or fats are broken down. 10  4- Nucleotides The fourth type of organic compound important to human structure and function are the nucleotides. nucleotide is one of a class of organic compounds composed of three subunits: one or more phosphate groups a pentose sugar: either deoxyribose or ribose a nitrogen-containing base: adenine, cytosine, guanine, thymine, or uracil Nucleotides can be assembled into nucleic acids (DNA or RNA) or the energy compound adenosine triphosphate. 11 12 Nucleic Acids The nucleic acids differ in their type of pentose sugar. Deoxyribonucleic acid (DNA) is nucleotide that stores genetic information. DNA contains deoxyribose (so-called because it has one less atom of oxygen than ribose) plus one phosphate group and one nitrogen-containing base. The base for DNA are adenine, cytosine, guanine, and thymine. Ribonucleic acid (RNA) is a ribose-containing nucleotide that helps manifest the genetic code as protein. RNA contains ribose, one phosphate group, and one nitrogen-containing base, but the base for RNA are adenine, cytosine, guanine, and uracil. 13  The nitrogen-containing bases adenine and guanine are classified as purines. A purine is a nitrogen-containing molecule with a double ring structure, which accommodates several nitrogen atoms. The bases cytosine, thymine (found in DNA only) and uracil (found in RNA only) are pyramidines. A pyramidine is a nitrogen-containing base with a single ring structure 14  Adenosine triphosphate (ATP) ATP is a nucleotide which contains ribose (the sugar unit), adenine (the base) and three phosphate groups attached to the ribose. It is sometimes known as the energy currency of the body, which implies that the body has to 'earn' (synthesis) it before it can 'spend' it. Many of the body's huge number of reactions release energy, e.g. the breakdown of sugars in the presence of O2. 15  The Nucleus Enclosed by a double membrane called the nuclear envelope. The nuclear envelope: – controls the entry and exit of materials between the nucleus and the cytoplasm. The cell nucleus may contain one or more nucleoli. Nucleoli: – are responsible for making the small and the large subunits of ribosomes. 16  Chromatin and DNA DNA is the genetic material housed within the nucleus. – DNA is a polymer of nucleotides (sugar, phosphate, nitrogen base) – Is a double helix. – Chromatin: Strands of DNA and histone proteins – Euchromatin: uncoiled; active – Heterochromatin: coiled. inactive 17  Insert Figure 2.18 18  Chromosome The chromosome is the most organized level of genetic material. Each chromosome contains a single, long molecule of DNA and associated proteins. Chromosomes become visible only when the cell is dividing. 19  PROTOZOA CLASSIFICATION OF PROTOZOA Sarcodina Single-celled Motility by pseudopodia Cysts and trophozoite Entamoeba histolytica (amoebae) forms Asexual reproduction Mastigophora Single-celled Giardia lamblia (flagellates) Movement chiefly by flagella Leishmania species Cysts and trophozoites for intestinal organisms Trichomonas spp. Asexual reproduction Trypanosoma species Blood flagellates may be included Ciliophora Single-celled Balantidium coli (ciliates) Movement chiefly by cilia Cysts and trophozoites stages Asexual reproduction Apicomplexa Single-celled Babesia microti Coccidia Inhabit host’s cells Cryptosporidium parvum Life cycle complex and involves insects, mammals other than host Isospora belli Both sexual and asexual reproduction may be involved Plasmodium species Toxoplasma gondii 1  Characteristics of Protozoa 1. Number of cells Unicellular 2. Mode of multiplication Asexual (with exception) 3. Infection caused by Multiplication 4. Rate of Multiplication Fast 5. Longivity Short 2 3 4 5  Trypanosoma spp. Americana trypanosoma cause Chagas disease and the vectors is the bloodsucking bugs African trypanosomiasis or acute African sleeping sickness. is spread by the tsetse fly 6 LEISHMANIA : cause Vector: sand fly 7 8  PLASMODIUM: causes malaria 9 Cause 10 viruses 1  viruses In the opinion of most biologists viruses are not living. This is based primarily on the absence of two major characteristics associated with living things: viruses are not cellular and they have no metabolism. On the other hand, they do exhibit heredity and are made of biochemicals. Proteins form the structures and receptors of the virus particle (not cell!), and DNA or RNA (all cellular organisms use DNA) is the hereditary material. And, whereas cells always possess both DNA and RNA (for protein synthesis), viruses have only one or the other and use it as the genome. They are also very small, usually much smaller than bacteria. They are capable of making more of themselves 2 (replication), but require a cellular host to do the work. As such, they are obligate intracellular parasites. And, unlike cells that remain intact when they reproduce, viruses disassemble during replication, then the progeny reassemble prior to release from the host—hence “viral replication” rather than “viral reproduction.” A virus particle consists minimally of a protein capsid surrounding its genome. The capsid is one of two basic geometric shapes and is composed of protein subunits called capsomeres. Some viruses have an icosahedral capsid with 20 triangular faces in which capsomeres combine to form the faces. Others have a rod shape in which the capsomeres form a helix and the genome is threaded in the helical grooves Others (typically viruses that infect animals) have an outer envelope composed of membrane obtained from the host cell upon release. 3 Viral replication involves the same basic stages, regardless of the host. These are: attachment to the host, penetration into the host, uncoating of the genome, genome replication and synthesis of viral proteins, assembly of progeny, and release. illustrates the replicative cycle of bacteriophage T4. The viral genome is either DNA or RNA. Further, some DNA viruses have double-stranded DNA (dsDNA), whereas others have single- stranded DNA (ssDNA), which does not exist in cells. RNA viruses can also have ssRNA or dsRNA. David Baltimore devised a viral taxonomy based on viral genome and the steps necessary to get information from the genome to messenger RNA. 4 By convention, mRNA is considered to be “+” sense. A strand of DNA or RNA complementary to it is considered “–” sense. There are six categories. 1 “+” ssRNA viruses. The genome acts as messenger RNA. A “–” ssRNA molecule is synthesized from the “+” ssRNA and acts as the template for genome replication and mRNA synthesis. Examples are poliovirus, hepatitis A and C viruses, and West Nile virus. 2 _ssRNA viruses. These viruses synthesize “+” ssRNA from the genome that acts as mRNA and as a template for genome replication. Examples include rabies virus, Ebola virus, measles virus, mumps virus, and influenza A virus. 3 dsRNA viruses. The negative strand is used to produce “+” ssRNA that acts as mRNA. Both strands are used as templates for genome replication. Examples include rotavirus (gastroenteritis) and reovirus (mild respiratory and digestive symptoms). 5 4 dsDNA viruses. These viruses make mRNA and replicate their genomes just as cells do. Examples include herpes simplex viruses, variola virus (small pox), and human papillomaviruses (cervical cancer and genital warts). 5 ssDNA viruses. These viruses must first replicate their genome to dsDNA, which is then used for transcription to mRNA. Normal DNA replication provides more ssDNA for the progeny genome. In most instances, only one “sense” of the ssDNA is packaged into the viral progeny, but there are exceptions where the progeny end up with one or the other. An example is human parvo virus B19 (which causes Fifth disease—a rash, seen mostly 6 in children).  viruses 6 “+” ssRNA retroviruses. Retroviruses are capable of using an RNA template to make dsDNA, which is then incorporated into the host genome and becomes latent. When active, transcription produces “+” ssRNA, which can be used as mRNA or genome for the progeny. Examples include Human Immunodeficiency Viruses (HIV—causes AIDS) and Human T-lymphotrophic. Viruses (HTLV—causes T-cell leukemia). 7 Organization and Functions of the Respiratory System Structural classifications: – upper respiratory tract – lower respiratory tract. Functional classifications: – Conducting portion: transports air. Nose nasal cavity Pharynx Larynx Trachea progressively smaller airways, from the primary bronchi to the bronchioles 25-1 Organization and Functions of the Respiratory System Functional classifications: continued – Conducting portion: transports air. – Respiratory portion: carries out gas exchange. respiratory bronchioles alveolar ducts air sacs called alveoli Upper respiratory tract is all conducting Lower respiratory tract has both conducting and respiratory portions 25-2 3 Respiratory System Functions Breathing (pulmonary ventilation): – consists of two cyclic phases: inhalation, also called inspiration exhalation, also called expiration – Inhalation draws gases into the lungs. – Exhalation forces gases out of the lungs. Gas exchange: O2 and CO2 – External respiration External environment and blood – Internal respiration Blood and cells 25-4 Respiratory System Functions Gas conditioning: – Warmed – Humidified – Cleaned of particulates Sound production: – Movement of air over true vocal cords – Also involves nose, paranasal sinuses, teeth, lips and tongue Olfaction: – Olfactory epithelium over superior nasal conchae Defense: – Course hairs, mucus, lymphoid tissue 25-5  Upper Respiratory Tract Composed of – the nose – the nasal cavity – the paranasal sinuses – the pharynx (throat) – and associated structures. All part of the conducting portion of the respiratory system. 25-6 7  Paranasal Sinuses Paranasal sinuses: – In four skull bones – paired air spaces – decrease skull bone weight Named for the bones in which they are housed. – frontal – ethmoidal – sphenoidal – maxillary Communicate with the nasal cavity by ducts. Covered with the same pseudostratified ciliated columnar epithelium as the nasal cavity. 25-8 9  Pharynx Common to both the respiratory and digestive systems. Commonly called the throat. Funnel-shaped – slightly wider superiorly and narrower inferiorly. Originates posterior to the nasal and oral cavities Extends inferiorly near the level of the bifurcation of the larynx and esophagus. Common pathway for both air and food. 25-10 11  Pharynx Walls: – lined by a mucosa – contain skeletal muscles primarily used for swallowing. Flexible lateral walls – distensible – to force swallowed food into the esophagus. Partitioned into three adjoining regions: – nasopharynx – oropharynx – laryngopharynx 25-12  Nasopharynx Superior most region of the pharynx. Location: – posterior to the nasal cavity – superior to the soft palate separates it from the posterior part of the oral cavity. Normally, only air passes through. Soft palate – Blocks material from the oral cavity and oropharynx – elevates when we swallow. Auditory tubes – paired – In the lateral walls of the nasopharynx – connect the nasopharynx to the middle ear. Pharyngeal tonsil – posterior nasopharynx wall – single – commonly called the adenoids. 25-13  Oropharynx The middle pharyngeal region. Location: – Immediately posterior to the oral cavity. – Bounded by the soft palate superiorly, – the hyoid bone inferiorly. Common respiratory and digestive pathway – both air and swallowed food and drink pass through. 2 pairs of muscular arches – anterior palatoglossal arches – posterior palatopharyngeal arches – form the entrance from the oral cavity. Lymphatic organs – provide the “first line of defense” against ingested or inhaled foreign materials. – Palatine tonsils on the lateral wall between the arches – Lingual tonsils 25-14 At the base of the tongue.  Laryngopharynx Inferior, narrowed region of the pharynx. Location: – Extends inferiorly from the hyoid bone – is continuous with the larynx and esophagus. – Terminates at the superior border of the esophagus is equivalent to the inferior border of the cricoid cartilage in the larynx. The larynx (voice box) forms the anterior wall Lined with a nonkeratinized stratified squamous epithelium (mucus membrane) Permits passage of both food and air. 25-15  Lower Respiratory Tract Conducting portion – Larynx – Trachea – Bronchi – bronchioles and their associated structures Respiratory portion of the respiratory system – respiratory bronchioles – alveolar ducts – alveoli 25-16  Larynx Short, somewhat cylindrical airway Location: – bounded posteriorly by the laryngopharynx, – inferiorly by the trachea. Prevents swallowed materials from entering the lower respiratory tract. Conducts air into the lower respiratory tract. Produces sounds. 25-17  Larynx Nine pieces of cartilage – three individual pieces Thyroid cartilage Cricoid cartilage Epiglottis – three cartilage pairs Arytenoids: on cricoid Corniculates: attach to arytenoids Cuniforms:in aryepiglottic fold – held in place by ligaments and muscles. Intrinsic muscles: regulate tension on true vocal cords Extrinsic muscles: stabilize the larynx 25-18 19  Sound Production Two pairs of ligaments Inferior ligaments, called vocal ligaments – covered by a mucous membrane – vocal folds: ligament and mucosa. – are “true vocal cords” they produce sound when air passes between them Superior ligaments, called vestibular ligaments – Covered by mucosa – vestibular folds: ligament and mucosa – Are “false vocal cords” no function in sound production protect the vocal folds. – The vestibular folds attach to the corniculate cartilages. 25-20  Sound Production The tension, length, and position of the vocal folds determine the quality of the sound. – Longer vocal folds produce lower sounds – More taunt, higher pitch – Loudness based on force of air Rima glottidis: opening between the vocal folds Glottis: rima glottidis and the vocal folds 25-21 22 23 24  Trachea A flexible, slightly rigid tubular organ – often referred to as the “windpipe.” Extends through the mediastinum – immediately anterior to the esophagus – inferior to the larynx – superior to the primary bronchi of the lungs. Anterior and lateral walls of the trachea are supported by 15 to 20 C-shaped tracheal cartilages. – cartilage rings reinforce and provide some rigidity to the tracheal wall to ensure that the trachea remains open (patent) at all times – cartilage rings are connected by elastic sheets 25-25 called anular ligaments 26  Trachea At the level of the sternal angle, the trachea bifurcates into two smaller tubes, called the right and left primary bronchi. Each primary bronchus projects laterally toward each lung. The most inferior tracheal cartilage separates the primary bronchi at their origin and forms an internal ridge called the carina. 25-27  Bronchial Tree A highly branched system – air-conducting passages – originate from the left and right primary bronchi. Progressively branch into narrower tubes as they diverge throughout the lungs before terminating in terminal bronchioles. Primary bronchi – Incomplete rings of hyaline cartilage ensure that they remain open. – Right primary bronchus shorter, wider, and more vertically oriented than the left primary bronchus. – Foreign particles are more likely to lodge in the 25-28 right primary bronchus.  Bronchial Tree Primary bronchi – enter the hilum of each lung – Also entering hilum: pulmonary vessels lymphatic vessels nerves. Secondary bronchi (or lobar bronchi) – Branch of primary bronchus – left lung: two lobes two secondary bronchi – right lung three lobes three secondary bronchi. Tertiary bronchi (or segmental bronchi) – Branch of secondary bronchi – left lung is supplied by 8 to 10 tertiary bronchi. – right lung is supplied by 10 tertiary bronchi – supply a part of the lung called a bronchopulmonary segment. 25-29 30 31  Respiratory Bronchioles, Alveolar Ducts, and Alveoli Contain small saccular outpocketings called alveoli. An alveolus is about 0.25 to 0.5 millimeter in diameter. Its thin wall is specialized to promote diffusion of gases between the alveolus and the blood in the pulmonary capillaries. Gas exchange can take place in the respiratory bronchioles and alveolar ducts as well as in the lungs, which contain approximately 300–400 million alveoli. The spongy nature of the lung is due to the packing of millions of alveoli together. 25-32 33 34 35 36  Gross Anatomy of the Lungs Each lung has a conical shape. Its wide, concave base rests upon the muscular diaphragm. Its relatively blunt superior region, called the apex or (cupola), projects superiorly to a point that is slightly superior and posterior to the clavicle. Both lungs are bordered by the thoracic wall anteriorly, laterally, and posteriorly, and supported by the rib cage. Toward the midline, the lungs are separated from each other by the mediastinum. The relatively broad, rounded surface in contact with the thoracic wall is called the costal surface of the lung. 25-37 38 39 40 41 42  Pleura and Pleural Cavities The outer surface of each lung and the adjacent internal thoracic wall are lined by a serous membrane called pleura, which is formed from simple squamous epithelium. The outer surface of each lung is tightly covered by the visceral pleura, while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura. The parietal and visceral pleural layers are continuous at the hilum of each lung. 25-43  Pleura and Pleural Cavities The outer surface of each lung is tightly covered by the visceral pleura, while the internal thoracic walls, the lateral surfaces of the mediastinum, and the superior surface of the diaphragm are lined by the parietal pleura. The potential space between these serous membrane layers is a pleural cavity. The pleural membranes produce a thin, serous fluid that circulates in the pleural cavity and acts as a lubricant, ensuring minimal friction during breathing. 25-44 45 46  Boyle’s Law “The pressure of a gas decreases if the volume of the container increases, and vice versa.” When the volume of the thoracic cavity increases even slightly during inhalation, the intrapulmonary pressure decreases slightly, and air flows into the lungs through the conducting airways. Air flows into the lungs from a region of higher pressure (the atmosphere) into a region of lower pressure (the intrapulmonary region). When the volume of the thoracic cavity decreases during exhalation, the intrapulmonary pressure increases and forces air out of the lungs into the atmosphere. 25-47  Ventilation Control by Respiratory Centers of the Brain The trachea, bronchial tree, and lungs are innervated by the autonomic nervous system. The autonomic nerve fibers that innervate the heart also send branches to the respiratory structures. The involuntary, rhythmic activities that deliver and remove respiratory gases are regulated in the brainstem. Regulatory respiratory centers are located within the reticular formation through both the medulla oblongata and pons. 25-48 49  Aging and the Respiratory System Becomes less efficient with age due to several structural changes. Decrease in elastic connective tissue in the lungs and the thoracic cavity wall. Loss of elasticity reduces the amount of gas that can be exchanged with each breath and results in a decrease in the ventilation rate. Emphysema may cause a loss of alveoli or their functionality Reduced capacity for gas exchange can cause an older person to become “short of breath” upon exertion. Carbon, dust, and pollution material gradually accumulate in our lymph nodes and lungs. 25-50 51 Digestive System General Structure and Functions of the Digestive System ◼ Organs of the Digestive System to: ◼ Ingest the food. ◼ Transport the food. ◼ Digest the food into smaller usable components. ◼ Absorb the necessary nutrients into the bloodstream. ◼ Expel the waste products from the body. General Structure and Functions of the Digestive System ◼ Composed of two separate categories of organs: ◼ digestive organs ◼ accessory digestive organs. ◼ Digestive organs collectively make up the: ◼ gastrointestinal (GI) tract. ◼ Also called: ◼ the digestive tract ◼ alimentary canal. General Structure and Functions of the Digestive System ◼ The GI tract organs: ◼ oral cavity ◼ pharynx ◼ esophagus ◼ stomach ◼ small intestine ◼ large intestine ◼ continuous tube ◼ about 30 feet (9–10 meters) ◼ from mouth to anus. ◼ Smooth muscle in the wall ◼ responsible for motility ◼ pushes materials from one end to the other. General Structure and Functions of the Digestive System ◼ Accessory digestive organs: ◼ do not form the GI tube ◼ can develop as outgrowths ◼ are connected to the GI tract (some by ducts) ◼ Assist the GI tract in the digestion of food. ◼ Include: ◼ Teeth ◼ Tongue ◼ Salivary glands ◼ Liver ◼ Gallbladder ◼ Pancreas Digestive System Functions ◼ Ingestion ◼ Digestion: break down of large particles of food ◼ mechanical digestion ◼ chemical digestion ◼ Propulsion ◼ peristalsis ◼ segmentation ◼ Secretion: ◼ digestive enzymes ◼ hormones ◼ Absorption: ◼ from external environment into internal environment ◼ across mucosa ◼ Elimination of wastes (defecation) Oral Cavity (mouth) ◼ Entrance to the GI tract. ◼ Initial site of digestion: ◼ mechanical digestion (via mastication) ◼ chemical digestion (via enzymes in saliva). ◼ Bounded anteriorly by the teeth and lips ◼ Bounded posteriorly by the oropharynx. ◼ Superior boundary is formed by the hard and soft palates. ◼ Floor, or inferior surface, of the oral cavity ◼ the tongue ◼ the mylohyoid muscle covered with mucosa. Oral Cavity (mouth) ◼ Two regions of the oral cavity ◼ Vestibule is the space between the cheeks or lips and the gums. ◼ Oral cavity proper. ◼ The lateral walls are formed by the cheeks. ◼ Contain buccinator muscles ◼ Lips (labia). ◼ Orbicularis oris muscle ◼ Keratinized stratified squamous ET ◼ Gingivae, or gums. ◼ Dense regular CT ◼ Nonkeratinized ET ◼ Labial frenulum. Palate ◼ Hard palate ◼ Anterior two-thirds of the palate ◼ hard and bony ◼ Soft palate ◼ Posterior one-third ◼ soft and muscular ◼ primarily composed of skeletal muscle. ◼ Extending inferiorly from the posterior part of the soft palate is the uvula. ◼ When swallowing, the soft palate and the uvula elevate to close off the opening of the nasopharynx. Palate ◼ Fauces represent the opening between the oral cavity and the oropharynx. ◼ Fauces are bounded by paired muscular folds: ◼ glossopalatine arch (anterior fold) ◼ pharyngopalatine arch (posterior fold) ◼ Palatine tonsils are housed between the arches. Tongue ◼ An accessory digestive organ ◼ Formed from: ◼ skeletal muscle ◼ covered with lightly keratinized stratified squamous epithelium. ◼ Manipulates and mixes ingested materials during chewing ◼ Forms the bolus. ◼ a globular mass of partially digested material ◼ Performs important functions in swallowing. Tongue ◼ Inferior surface of the tongue ◼ attaches to the floor of the oral cavity ◼ By the lingual frenulum. ◼ Numerous small projections (papillae) cover the superior (dorsal) surface. ◼ Posterior surface contains lingual tonsils. ◼ Skeletal muscles move the tongue. Salivary Glands ◼ Collectively produce and secrete saliva. ◼ a fluid that assists in the initial activities of digestion ◼ Volume of saliva secreted daily ranges between 1.0 and 1.5 L. ◼ Most is produced during mealtime ◼ Smaller amounts are produced continuously to ensure that the oral cavity remains moist. Salivary Glands ◼ Components of saliva ◼ Water: makes up 99% ◼ Amylase: first step of chemical digestion ◼ Lysozyme: antimicrobial ◼ Functions ◼ Moisten food ◼ Food molecules into solution: taste ◼ Form bolus: for swallowing ◼ Cleanse oral cavity. Salivary Glands ◼ Three pairs of large, multicellular salivary glands: ◼ parotid glands ◼ submandibular glands ◼ sublingual glands The Parotid Glands ◼ Largest salivary glands. ◼ located anterior and inferior to the ear ◼ partially overlying the masseter muscle. ◼ Produce about 25–30% of saliva ◼ conducted through the parotid duct to the oral cavity. The Submandibular Glands ◼ Inferior to the body of the mandible. ◼ Produce most of the saliva (about 60– 70%). ◼ ducts opens through a papilla in the floor of the mouth ◼ lateral to the the lingual frenulum. The Sublingual Glands ◼ Inferior to the tongue ◼ internal to the oral cavity mucosa. ◼ Each gland has multiple tiny sublingual ducts ◼ open onto the inferior surface of the oral cavity ◼ posterior to the submandibular duct papilla. ◼ Contribute only about 3–5% of the total saliva. Teeth ◼ Collectively known as the dentition. ◼ Responsible for mastication ◼ first part of the mechanical digestion. ◼ A tooth has: ◼ exposed crown ◼ constricted neck ◼ one or more roots ◼ Roots of the teeth fit into dental alveoli ◼ are sockets within the alveolar processes ◼ on both the maxillae and the mandible. ◼ Collectively, the roots, the dental alveoli, and the periodontal ligament that binds the roots to the alveolar processes form a gomphosis joint. Teeth ◼ Two sets of teeth ◼ 20 deciduous teeth, also called “milk teeth,” erupt between 6 months and 30 months after birth. ◼ These teeth are eventually lost and replaced by 32 permanent teeth. ◼ The more anteriorly placed permanent teeth tend to appear first, followed by the posteriorly placed teeth. ◼ The last teeth to erupt are the third molars, often called “wisdom teeth,” in the late teens or early 20’s. ◼ Often the jaw lacks space to accommodate these final molars, and they may either emerge only partially or grow at an angle and become impacted. ◼ Impacted teeth cannot erupt properly because of the angle of their growth. Pharynx ◼ Review ◼ Pharyngeal constrictors ◼ Innervated by the vagus nerves General arrangement of abdominal GI organs ◼ Peritoneum ◼ Parietal peritoneum ◼ Visceral peritoneum ◼ Peritoneal cavity ◼ Intraperitoneal organs ◼ Retroperitoneal organs General arrangement of abdominal GI organs ◼ Mesentaries ◼ Double layered folds of peritoneum ◼ Greater omentum ◼ Lesser omentum ◼ Mesentery proper ◼ Suspends small intestine from posterior wall of abdomen ◼ Mesocolon ◼ Suspends large intestine ◼ Peritoneal ligament ◼ Peritoneum that attaches one organ to another General Histology of GI Organs ◼ from the esophagus through the large intestine ◼ a tube ◼ composed of four concentric layers called tunics. ◼ From deep to superficial, these tunics are: ◼ the mucosa ◼ the submucosa ◼ submucosal nerve plexus (Meissner plexus) ◼ the muscularis ◼ myenteric plexus (Auerbach plexus) ◼ the adventitia or serosa Esophagus ◼ Tubular passageway ◼ Pharynx to stomach ◼ Bolus ◼ About 25 cm in adult ◼ Esophageal hiatus: through diaphragm ◼ Histology ◼ Mucosa: nonkeritinized stratified squamous ep. ◼ Submucosa: thick, elastic fibers, mucous glands ◼ Muscularis: inner circular, outer longitudinal ◼ Both skeletal and smooth ◼ Adventitia Esophagus ◼ Superior esophageal sphincter: ◼ Skeletal muscle ◼ Where pharynx and esophagus meet ◼ Inferior esophageal sphincter ◼ Also cardiac sphincter ◼ Circular smooth muscle ◼ Orifice between esophagus and stomach Stomach ◼ General ◼ J-shaped ◼ Functions ◼ Digestion ◼ Chemical ◼ Mechanical ◼ Results in chyme ◼ Limited absorption Stomach ◼ Gross anatomy ◼ Cardia ◼ Cardiac orifice ◼ Fundus ◼ Body ◼ Pylorus ◼ Pyloric sphincter ◼ Pyloric orifice ◼ Greater curvature ◼ Greater omentum ◼ Lesser curvature ◼ Lesser omemtum ◼ Gastric folds (rugae) Stomach ◼ Histology ◼ Mucosa: simple columnar ◼ Gastric pits ◼ Gastric glands ◼ Muscularis ◼ 3 layers ◼ Inner oblique ◼ Middle circular ◼ Outer longitudinal Small Intestine ◼ Finishes chemical digestion ◼ Responsible for absorbing most of the nutrients. ◼ Ingested nutrients spend at least 12 hours in the small intestine. ◼ thin-walled tube ◼ about 6 meters (20 feet) in length. ◼ coiled ◼ Extends from the pylorus of the stomach to the cecum of the large intestine ◼ occupies a significant portion of the abdominal cavity. Small Intestine ◼ The duodenum ◼ first segment of the small intestine. ◼ approximately 25 centimeters (10 inches) long ◼ originates at the pyloric sphincter ◼ major duodenal papilla ◼ The jejunum ◼ middle region of the small intestine. ◼ approximately 2.5 meters (7.5 feet) ◼ makes up approximately two-fifths of the small intestine’s total length. ◼ primary region for chemical digestion and nutrient absorption ◼ The ileum ◼ is the last region of the small intestine. ◼ about 3.6 meters (10.8 feet) in length ◼ forms approximately three-fifths of the small intestine. ◼ terminates at the ileocecal valve ◼ sphincter that controls the entry of materials into the large intestine. Large Intestine ◼ approximate length of 1.5 meters (5 feet) ◼ diameter of 6.5 centimeters (2.5 inches). ◼ Absorbs most of the water and electrolytes from the remaining digested material. ◼ Watery material that first enters the large intestine soon solidifies and becomes feces. ◼ Stores fecal material until the body is ready to defecate. ◼ Absorbs a very small percentage of nutrients still remaining in the digested material. ◼ Composed of four segments: ◼ the cecum, colon, rectum, anal canal Accessory Digestive Organs ◼ The liver ◼ composed of four incompletely separated lobes ◼ supported by two ligaments ◼ Right lobe ◼ Left lobe ◼ Falciform ligament ◼ Round ligament ◼ Caudate lobe ◼ Quadrate lobe Functions of The Liver ◼ Produce bile. ◼ a greenish fluid that breaks down fats into small droplets to assist in their chemical digestion ◼ Detoxify drugs, metabolites, and poisons. ◼ Store excess nutrients and vitamins and release them when they are needed. ◼ Synthesize blood plasma proteins such as albumins, globulins, and proteins required for blood clotting. ◼ Phagocytize debris in the blood. ◼ Help break down and recycle components of aged erythrocytes and damaged or worn-out formed elements.  Accessory Digestive Organs The liver – composed of four incompletely separated lobes – supported by two ligaments Right lobe Left lobe Falciform ligament Round ligament Caudate lobe Quadrate lobe Accessory Digestive Organs ◼ Gallbladder ◼ concentrates bile produced by the liver and stores this concentrate until it is needed for digestion ◼ cystic duct connects the gallbladder to the common bile duct ◼ can hold approximately 40 to 60 milliliters of concentrated bile Accessory Digestive Organs ◼ Pancreas ◼ mixed gland because it exhibits both endocrine and exocrine functions ◼ Endocrine functions are performed by the pancreatic islets. ◼ Exocrine activity results in the secretion of digestive enzymes, collectively called pancreatic juice, into the duodenum. Accessory Digestive Organs ◼ The biliary apparatus. ◼ network of thin ducts that carry bile from the liver and gallbladder to the duodenum ◼ the left and right lobes of the liver drain bile into the left and right hepatic ducts, respectively ◼ the left and right hepatic ducts merge to form a single common hepatic duct ◼ the cystic duct attaches to the common hepatic duct and carries bile to and from the gallbladder The Cardiovascular System The Heart 1  Heart Anatomy Approximately the size of your fist Location – Superior surface of diaphragm – Left of the midline – Anterior to the vertebral column, posterior to the sternum 2  Coverings of the Heart: Anatomy Pericardium – a double-walled sac around the heart composed of: 1. A superficial fibrous pericardium 2. A deep two-layer serous pericardium a. The parietal layer lines the internal surface of the fibrous pericardium b. The visceral layer or epicardium lines the surface of the heart They are separated by the fluid-filled pericardial cavity 3 Pericardial Layers of the Heart 4  Heart Wall Epicardium – visceral layer of the serous pericardium Myocardium – cardiac muscle layer forming the bulk of the heart Fibrous skeleton of the heart – crisscrossing, interlacing layer of connective tissue Endocardium – endothelial layer of the inner myocardial surface 5  Chambers of the Heart Atria of the Heart Atria: are the receiving chambers of the heart Each atrium has a protruding auricle Pectinate muscles mark atrial walls Blood enters right atria from superior and inferior venae cavae and coronary sinus Blood enters left atria from pulmonary veins 6  Ventricles of the Heart Ventricles are the discharging chambers of the heart Papillary muscles and trabeculae carneae muscles mark ventricular walls Right ventricle pumps blood into the pulmonary trunk Left ventricle pumps blood into the aorta 7  Heart Valves Heart valves ensure unidirectional blood flow through the heart Atrioventricular (AV) valves lie between the atria and the ventricles – AV valves prevent backflow into the atria when ventricles contract Chordae tendineae anchor AV valves to papillary muscles 8  Heart Valves Semilunar valves prevent backflow of blood into the ventricles Aortic semilunar valve lies between the left ventricle and the aorta Pulmonary semilunar valve lies between the right ventricle and pulmonary trunk 9  Microscopic Anatomy of Heart Muscle Cardiac muscle is striated, short, fat, branched, and interconnected The connective tissue endomysium acts as both tendon and insertion Intercalated discs anchor cardiac cells together and allow free passage of ions Heart muscle behaves as a functional syncytium 10 Microscopic Anatomy of Heart Muscle 11  Blood Vessels Arteries, veins, and capillaries Vessels conveying blood away from the heart are arteries Vessels returning blood to the heart are veins Vessels that contact with the Heart: veins: 1. Superior and inferior venae cavae 2. Right and left pulmonary veins arteries: 1. Pulmonary trunk, which splits into right and left pulmonary arteries 2. Ascending aorta (three branches) – a. Brachiocephalic b. Left common carotid 12 c. Subclavian arteries External Heart: Anterior View 13 Gross Anatomy of Heart: Frontal Section 14 15 Comparison between a vein and its companion muscular artery Both are tubes lined by endothelium and may contain RBCs. Artery Vein (a) Shape less deformed (a) Flattened (b) Thick wall (b) Thin wall (c) Intima crinkled (c) Intima smooth (d) Three distinct layers (d) Layering indistinct (media prominent) (media weak) (e) Internal elastic lamina (e) No internal elastic lamina 16 17  Reproductive Systems ◼ Main function: propagation of the species ◼ To achieve this goal: ◼ Must ensure sexual maturation ◼ Produce gametes (n). ◼ Male and female structures are homologues: ◼ derived from common developmental tissues Comparison of the Female and Male Reproductive Systems ◼ Primary sex organs called gonads. ◼ ovaries in females ◼ testes in males ◼ Produce gametes which unite to form a new individual. ◼ oocytes ◼ sperm ◼ Gonads produce large amounts of sex hormones which affect maturation, development, and changes in the activity of the reproductive system organs. ◼ estrogen and progesterone in the female ◼ androgens (esp. testosterone) in the male Comparison of the Female and Male Reproductive Systems ◼ Both have accessory reproductive organs ◼ duct systems ◼ carry gametes away from the gonads ◼ toward the site of fertilization in females ◼ to the outside of the body in males ◼ Fertilization occurs when male and female gametes meet: ◼ copulation, coitus, sexual intercourse ◼ Restores the diploid number (2n) Comparison of the Female and Male Reproductive Systems ◼ Primarily nonfunctional and “dormant” until puberty. ◼ At puberty, external sex characteristics become more prominent. ◼ breast enlargement in females ◼ fat distribution patterns in both sexes ◼ pubic hair in both sexes ◼ reproductive organs become fully functional ◼ gametes mature ◼ gonads secrete sex hormones ◼ Both reproductive systems produce gametes. Comparison of the Female and Male Reproductive Systems ◼ Puberty: ◼ Initiated by hypothalamus ◼ Secretes GnRH (gonadotropin-releasing hormone ◼ Stimulates release of FSH and LH ◼ Prior to puberty, not present ◼ Stimulate gonads to produce: ◼ Sex hormones ◼ gametes Comparison of the Female and Male Reproductive Systems ◼ Female typically produces and releases a single oocyte monthly. ◼ Male produces 100,000,000’s of (sperm) daily. ◼ male gametes are stored for a short time ◼ if they are not expelled from the body within that period, they are resorbed Perineum ◼ Diamond-shaped area between the thighs that is circumscribed anteriorly by the pubic symphysis, laterally by the ischial tuberosities, and posteriorly by the coccyx. ◼ 2 distinct triangle bases ◼ formed by an imaginary horizontal line extending between the ischial tuberosities of the ossa coxae. ◼ Anterior triangle, or urogenital triangle ◼ contains the urethral and vaginal orifices in females ◼ contains the base of the penis and the scrotum in males. ◼ Posterior triangle, or anal triangle ◼ location of the anus in both sexes. Anatomy of the Female Reproductive System ◼ Peritoneum folds around the various pelvic organs and creates two major dead-end recesses, or pouches. ◼ anterior vesicouterine pouch forms the space between the uterus and the urinary bladder ◼ posterior rectouterine pouch forms the space between the uterus anteriorly and the rectum posteriorly ◼ Primary sex organs of the female are the ovaries. ◼ Accessory sex organs include ◼ uterine tubes ◼ uterus, ◼ vagina, ◼ clitoris ◼ mammary glands. ◼ Mesovarium: ◼ Double folds of peritoneum ◼ Attaches ovaries to broad ligament ◼ Broad ligament ◼ Peritonium ◼ Drapes over the uterus ◼ Ovarian ligament ◼ Ovary to uterus ◼ Suspensory ligament ◼ Ovary to pelvic wall Ovarian Follicles ◼ Within the cortex are thousands of ovarian follicles. ◼ Consist of ◼ Follicle cells ◼ granulosa cells ◼ nurse cells that support the oocyte ◼ a type of oocyte. ◼ Several different kinds of ovarian follicles, each representing a different stage of development. ◼ Oogenesis: ◼ maturation of a primary oocyte to a secondary oocyte. Before Birth ◼ The process of oogenesis occurs in a female fetus before birth. At this time, the ovary contains primordial germ cells called oogonia, which are diploid cells, meaning they have 23 pairs of chromosomes. ◼ During the fetal period, the oogonia start the process of meiosis, but they are stopped at prophase I. At this point, the cells are called primary oocytes. ◼ At birth, the ovary of a female child is estimated to contain approximately 1.5 to 2 million primordial follicles within its cortex. ◼ The primary oocytes in the primordial follicles remain arrested in prophase I until after puberty. From Puberty to Menopause ◼ During childhood ovaries are inactive, and no follicles develop. ◼ Atresia occurs, in which some primordial follicles regress or break down. ◼ By the time she reaches puberty only about 400,000 primordial follicles remain. ◼ At puberty, the hypothalamus releases GnRH (gonadotropin- releasing hormone), which stimulates the anterior pituitary to release FSH (follicle-stimulating hormone) and LH (luteinizing hormone). ◼ The levels of FSH and LH vary in a cyclical pattern and produce a monthly ovarian cycle. ◼ The three phases of the ovarian cycle: are the follicular phase, ovulation, and the luteal phase. The Three Phases of the Ovarian Cycle ◼ Follicular phase occupies days 1–13 of an approximate 28-day ovarian cycle. ◼ Ovulation occurs on day 14 of a 28-day ovarian cycle and is defined as the release of the secondary oocyte from a vesicular follicle. ◼ only one ovary ovulates each month ◼ Luteal phase occurs during days 15–28 when the remaining follicle cells in the ruptured vesicular follicle turn into a corpus luteum. ◼ secretes progesterone and estrogen that stabilize and build up the uterine lining, and prepare for possible implantation of a fertilized oocyte ◼ has a life span of about 10–13 days if the secondary oocyte is not fertilized ◼ it regresses and becomes a corpus albicans ◼ the uterine lining to be shed as menstruation ◼ menarche After Menopause ◼ The time when a woman is nearing menopause is called perimenopause. ◼ estrogen levels begin to drop, and ◼ a woman may experience irregular periods, skip some periods, or have very light periods ◼ When a woman has stopped having monthly menstrual cycles for 1 year and is not pregnant, she is said to be in menopause. ◼ The age at onset typically is between 45 and 55 years ◼ follicles stop maturing, and significant amounts of estrogen and progesterone are no longer being secreted ◼ a woman’s endometrial lining does not grow, and she no longer has a menstrual period Uterine Tubes ◼ The uterine tubes, also called the fallopian tubes or oviducts, extend laterally from both sides of the uterus toward the ovaries. ◼ In these tubes, the secondary oocyte is fertilized, and the pre- embryo begins to develop as it travels toward the uterus. ◼ Usually it takes the pre-embryo about 5 to 6 days to reach the lumen of the uterus. ◼ Parts: lined with mucosa (simple ciliated columnar ep), muscularis, serosa ◼ Infundibulum ◼ Ampulla ◼ Isthmus ◼ Interstitial segment The Uterus Serves Four Functions ◼ Site for implantation. ◼ pre-embryo implants into the inner uterine wall and becomes connected to the uterine lining ◼ Supports, protects, and nourishes the developing embryo/fetus ◼ forms a vascular connection with the mother’s uterine wall that later develops into the placenta ◼ Ejects the fetus at birth after maternal oxytocin levels increase to initiate the uterine contractions of labor. ◼ Site for menstruation. ◼ if an oocyte is not fertilized or after a baby is expelled, the muscular wall of the uterus contracts and sheds its inner lining as menstruation Regions of the Uterus ◼ Fundus ◼ Body ◼ Isthmus ◼ Cervix ◼ Cervical canal ◼ Internal os ◼ External os Support of the Uterus ◼ Pelvic floor muscles ◼ Pelvic diaphragm ◼ Urogenital diaphragm ◼ Round ligaments ◼ Lateral uterus, through inguinal canal, to labia majora ◼ Maintain anteverted position ◼ Transverse cervical ligaments ◼ Lateral cervix and vagina to pelvic wall ◼ Uterosacral ligaments ◼ Inferior uterus to sacrum Wall of the Uterus ◼ Composed of three concentric tunics: ◼ Perimetrium ◼ Myometrium ◼ Endometrium ◼ The outer tunic of most of the uterus is a serosa called the perimetrium. ◼ continuous with the broad ligament ◼ The myometrium is the thick, middle tunic of the uterine wall formed from three intertwining layers of smooth muscle. ◼ in the nonpregnant uterus, the muscle cells are less than 0.25 millimeters in length ◼ during the course of a pregnancy, smooth muscle cells increase both in size and in number Uterine (Menstrual) Cycle and Menstruation ◼ The menstrual phase occurs approximately during days 1–5 of the cycle. This phase is marked by sloughing of the functional layer and lasts through the period of menstrual bleeding. ◼ The proliferative phase follows, spanning approximately days 6–14. The initial development of the functional layer of the endometrium overlaps the time of follicle growth and estrogen secretion. ◼ The last phase is the secretory phase, which occurs at approximately days 15–28. During the secretary phase, increased progesterone secretion from the corpus luteum results in increased vascularization and development of uterine glands. ◼ If the oocyte is not fertilized, the corpus luteum degenerates, and the progesterone level drops dramatically. ◼ Without progesterone, the functional layer lining sloughs off, and the next menstrual phase begins. Vagina ◼ The vagina is ◼ thick-walled, fibromuscular tube ◼ forms the inferior-most region of the female reproductive tract ◼ measures about 10 centimeters in length in an adult female. ◼ The vagina connects the uterus with the outside of the body anteroventrally ◼ functions as the birth canal. ◼ Also the copulatory organ of the female ◼ Serves as the passageway for menstruation. ◼ The vaginal wall is heavily invested with both blood vessels and lymphatic vessels. ◼ The vagina’s relatively thin, distensible wall consists of three tunics: ◼ an inner mucosa, a middle muscularis, and an outer adventitia External Genitalia ◼ The external sex organs of the female, are collectively called the vulva. ◼ The mons pubis is an expanse of skin and subcutaneous connective tissue immediately anterior to the pubic symphysis. ◼ covered with pubic hair in postpubescent females ◼ labia majora ◼ labia minora ◼ Contain the vestibule ◼ Urethral orifice ◼ Vaginal oriface ◼ Clitoris located at the anterior regions of the labia minora ◼ glans ◼ prepuce−an external fold of the labia minora that forms a hoodlike covering over the clitoris. Mammary Glands ◼ Each mammary gland, or breast, is located within the anterior thoracic wall and is composed of a compound tubuloalveolar exocrine gland. ◼ Breast milk contains proteins, fats, and a sugar to provide nutrition to infants. ◼ The nipple is a cylindrical projection on the center of the breast. It contains multiple tiny openings of the excretory ducts that produce breast milk. ◼ The areola is the pigmented rosy or brownish ring of skin around the nipple. Its surface often appears uneven and grainy due to the numerous sebaceous glands immediately internal to the surface. ◼ The color of the areola may vary, depending upon whether or not a woman has given birth. In a nulliparous woman (a woman who has never given birth), the areola is rosy or light brown in color. ◼ In a parous woman (a woman who has given birth), the areola may change to a darker rose or brown color. Anatomy of the Male Reproductive System ◼ Primary organs: gonads are the testes ◼ Accessory sex organs include: ◼ a complex set of ducts and tubules leading from the testes to the penis ◼ a group of male accessory glands ◼ the penis, which is the organ of copulation Scrotum ◼ Skin covered sac ◼ Raphe: external midline seam ◼ Continues on inferior surface of the penis, and to anus. ◼ Components of scrotal wall. ◼ Skin ◼ Fascia ◼ Dartos muscle ◼ External spermatic fascia ◼ Cremaster muscle ◼ Internal spermatic fascia ◼ Tunica vaginalis. ◼ Scrotum ◼ Male gametes are sensitive to elevated temperatures ◼ often exhibit abnormal or completely curtailed development ◼ Gamete development occurs outside the body ◼ Scrotum: a skin-covered sac that houses: ◼ male gonads ◼ first portion of the duct system ◼ site of early sperm maturation and development, reside outside the body proper. ◼ Testes exposed to elevated temperatures ◼ Skin of the scrotal sac becomes thin ◼ result of dartos muscle relaxation. ◼ The cremaster muscle relaxes ◼ allows the testes to move inferiorly away from the body ◼ The testes temperature becomes less than normal body temperature. ◼ The opposite occurs if the testes are exposed to cold. Testes ◼ Small, oval organ ◼ Housed in the scrotum ◼ Produces: ◼ Sperm ◼ androgens. ◼ Coverings ◼ Serous membrane called tunica vaginalis ◼ Parietal layer ◼ Visceral layer. ◼ Tunica albuginea ◼ Forms internal septa ◼ 250 lobules per testis ◼ Each lobule has up to 4 seminiferous tubules ◼ Two types of cell ◼ Sustentacular cells ◼ Germ cells ◼ Interior is called mediastinum testis. Testes ◼ Blood-testis barrier ◼ Tight junctions between sustentacular cells ◼ Spern develop in the semineferous tubules ◼ Interstitial spaces: surround the seminiferous tubules. ◼ Contain interstitial (Leydig) cells ◼ produce hormones called androgens. ◼ Several types of androgens ◼ most common one is testosterone. ◼ the adrenal cortex secretes a small amount of androgens ◼ the vast majority of androgen release is via interstitial cells in the testis ◼ beginning at puberty. ◼ These hormones cause males to develop the classic characteristics: ◼ axillary and pubic hair ◼ deeper voice ◼ sperm production.  Testes ◼ Series of tubes: ◼ Seminiferous tubules ◼ Straight ducts ◼ Rete testis ◼ Efferent ductule ◼ Epididymis ◼ Ductus deferens Spermatic Cord ◼ The blood vessels and nerves to the testis travel from within the abdomen to the scrotum in a multilayered structure called the spermatic cord. ◼ Layers ◼ Contain ◼ Testicular artery ◼ Pampiniform plexus ◼ Autonomic nerves Developmemt of sperm ◼ Called spermatogenesis ◼ Occurs in the seminiferous tubules ◼ Process: ◼ Spermatogonium ◼ Primary spermatocyte ◼ Secondary spermatocyte ◼ Spermatid ◼ Spermiogenesis ◼ Spermatid matures into spermatozoon Epididymis ◼ The epididymis is a comma-shaped structure composed of an internal duct and an external covering of connective tissue. ◼ Its head lies on the superior surface of the testis, while the body and tail are posterior to the testis. ◼ Internally, the epididymis contains a long, convoluted duct of the epididymis, which is approximately 4 to 5 meters in length. ◼ Sperm must reside in the epididymis for a period of time to become mature and fully motile. ◼ If they are expelled too soon, they lack the motility necessary to travel through the female reproductive tract and fertilize an oocyte. ◼ If sperm are not ejected from the male reproductive system in a timely manner, the old sperm degenerate in the epididymis. Ductus Deferens ◼ When sperm leave the epididymis, they enter the ductus deferens, also called the vas deferens. ◼ The ductus deferens is a thick-walled tube that travels within the spermatic cord, through the inguinal canal, and within the pelvic cavity before it reaches the prostate gland. ◼ The ampulla of the ductus deferens unites with the proximal region of the seminal vesicle to form the terminal portion of the reproductive duct system, called the ejaculatory duct. Urethra ◼ Transports semen from the ejaculatory duct to the outside of the body. ◼ Subdivided into: ◼ prostatic urethra that extends through the prostate gland ◼ membranous urethra that travels through the urogenital diaphragm ◼ penile urethra that ends through the penis ◼ Sperm leave the body through the urethra. Accessory Glands ◼ The vagina has a highly acidic environment to prevent bacterial growth. ◼ Sperm cannot survive in this type of environment, so an alkaline secretion called seminal fluid is needed to lessen the acidity of the vagina and bring pH values closer to neutral. ◼ As the sperm travel through the reproductive tract (a process that can take several days), they are nourished by nutrients within the seminal fluid. ◼ The components of seminal fluid are produced by accessory glands: ◼ seminal vesicles ◼ prostate gland ◼ bulbourethral glands Seminal Vesicles ◼ The paired seminal vesicles are located on the posterior surface of the urinary bladder adjacent to the ampulla of the ductus deferens. ◼ Each seminal vesicle is an elongated, pouchlike hollow organ approximately 5–8 centimeters long. ◼ It is the proximal portion of each seminal vesicle that merges with a ductus deferens to form the ejaculatory duct. ◼ The seminal vesicles secrete a viscous, whitish-yellow alkaline fluid containing both fructose and prostaglandins. ◼ The fructose is a sugar that nourishes the sperm as they travel through the female reproductive tract, while the prostaglandins promote the widening and slight dilation of the external os of the cervix. Prostate Gland ◼ A compact encapsulated organ that weighs about 20 grams and is shaped like a walnut, measuring approximately 2 cm by 3 cm by 4 cm. ◼ Located immediately inferior to the bladder. ◼ Secretes a slightly milky fluid that is weakly acidic and rich in citric acid, seminalplasmin, and prostate-specific antigen (PSA). ◼ citric acid is a nutrient for sperm health ◼ seminalplasmin is an antibiotic that combats urinary tract infections ◼ PSA acts as an enzyme to help liquefy semen following ejaculation Bulbourethral Glands ◼ Paired, pea-shaped ◼ Also called Cowper’s glands ◼ Location: ◼ within the urogenital diaphragm ◼ on each side of the membranous urethra. ◼ Each gland has a short duct ◼ projects into the base of the penis ◼ enters the spongy urethra. ◼ secretory product ◼ clear, viscous mucin (forms mucus when mixed with water). ◼ mucin protects the urethra ◼ serves as a lubricant during sexual intercourse. Semen ◼ Combination of seminal fluid from the accessory glands and sperm. ◼ Called the ejaculate (when released during ejaculation) ◼ normally about 3 to 5 milliliters ◼ contains approximately 200 to 500 million spermatozoa. ◼ Average transit time: about 2 weeks ◼ from release of sperm into the lumen of the seminiferous tubules, passage through the duct system, and appearance in the ejaculate. ◼ Sperm count can vary, semen amount usually remains the same. Aging and the Reproductive Systems ◼ Our reproductive systems are basically nonfunctional for several years following birth. When we reach puberty, hormonal changes in the hypothalamus and anterior pituitary gland stimulate the gonads to begin producing sex hormones. ◼ Thereafter, changes occur in many body structures, the reproductive organs mature, and gonads begin to produce gametes. ◼ Gametes stop maturing in females in their 40s or 50s, and menopause occurs. ◼ A reduction in hormone production that accompanies menopause causes some atrophy of the reproductive organs and the breasts. ◼ The vaginal wall thickness decreases, as do glandular secretions for maintaining a lubricated and moist lining. ◼ The uterus shrinks and atrophies, becoming much smaller than it was before puberty.